Cleanup: move public doc-strings into headers for 'blenlib'

- Added space below non doc-string comments to make it clear
  these aren't comments for the symbols directly below them.
- Use doxy sections for some headers.
- Minor improvements to doc-strings.

Ref T92709

1 files changed, 607 insertions, 28 deletions

diff --git a/source/blender/blenlib/BLI_math_geom.h b/source/blender/blenlib/BLI_math_geom.h
index be10b302144..539bb338032 100644
--- a/source/blender/blenlib/BLI_math_geom.h
+++ b/source/blender/blenlib/BLI_math_geom.h
@@ -37,16 +37,26 @@
 extern "C" {
 #endif
 
-/********************************** Polygons *********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Polygons
+ * \{ */
 
 float normal_tri_v3(float n[3], const float v1[3], const float v2[3], const float v3[3]);
 float normal_quad_v3(
     float n[3], const float v1[3], const float v2[3], const float v3[3], const float v4[3]);
+/**
+ * Computes the normal of a planar polygon See Graphics Gems for computing newell normal.
+ */
 float normal_poly_v3(float n[3], const float verts[][3], unsigned int nr);
 
 MINLINE float area_tri_v2(const float v1[2], const float v2[2], const float v3[2]);
 MINLINE float area_squared_tri_v2(const float v1[2], const float v2[2], const float v3[2]);
 MINLINE float area_tri_signed_v2(const float v1[2], const float v2[2], const float v3[2]);
+
+/* Triangles */
+
 float area_tri_v3(const float v1[3], const float v2[3], const float v3[3]);
 float area_squared_tri_v3(const float v1[3], const float v2[3], const float v3[3]);
 float area_tri_signed_v3(const float v1[3],
@@ -68,38 +78,88 @@ float cotangent_tri_weight_v3(const float v1[3], const float v2[3], const float
 void cross_tri_v3(float n[3], const float v1[3], const float v2[3], const float v3[3]);
 MINLINE float cross_tri_v2(const float v1[2], const float v2[2], const float v3[2]);
 void cross_poly_v3(float n[3], const float verts[][3], unsigned int nr);
+/**
+ * Scalar cross product of a 2d polygon.
+ *
+ * - equivalent to `area * 2`
+ * - useful for checking polygon winding (a positive value is clockwise).
+ */
 float cross_poly_v2(const float verts[][2], unsigned int nr);
 
-/********************************* Planes **********************************/
+/** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Planes
+ * \{ */
+
+/**
+ * Calculate a plane from a point and a direction,
+ * \note \a point_no isn't required to be normalized.
+ */
 void plane_from_point_normal_v3(float r_plane[4],
                                 const float plane_co[3],
                                 const float plane_no[3]);
+/**
+ * Get a point and a direction from a plane.
+ */
 void plane_to_point_vector_v3(const float plane[4], float r_plane_co[3], float r_plane_no[3]);
+/**
+ * Version of #plane_to_point_vector_v3 that gets a unit length vector.
+ */
 void plane_to_point_vector_v3_normalized(const float plane[4],
                                          float r_plane_co[3],
                                          float r_plane_no[3]);
 
 MINLINE float plane_point_side_v3(const float plane[4], const float co[3]);
 
-/********************************* Volume **********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Volume
+ * \{ */
 
+/**
+ * The volume from a tetrahedron, points can be in any order
+ */
 float volume_tetrahedron_v3(const float v1[3],
                             const float v2[3],
                             const float v3[3],
                             const float v4[3]);
+/**
+ * The volume from a tetrahedron, normal pointing inside gives negative volume
+ */
 float volume_tetrahedron_signed_v3(const float v1[3],
                                    const float v2[3],
                                    const float v3[3],
                                    const float v4[3]);
 
+/**
+ * The volume from a triangle that is made into a tetrahedron.
+ * This uses a simplified formula where the tip of the tetrahedron is in the world origin.
+ * Using this method, the total volume of a closed triangle mesh can be calculated.
+ * Note that you need to divide the result by 6 to get the actual volume.
+ */
 float volume_tri_tetrahedron_signed_v3_6x(const float v1[3], const float v2[3], const float v3[3]);
 float volume_tri_tetrahedron_signed_v3(const float v1[3], const float v2[3], const float v3[3]);
 
+/**
+ * Check if the edge is convex or concave
+ * (depends on face winding)
+ * Copied from BM_edge_is_convex().
+ */
 bool is_edge_convex_v3(const float v1[3], const float v2[3], const float v3[3], const float v4[3]);
+/**
+ * Evaluate if entire quad is a proper convex quad
+ */
 bool is_quad_convex_v3(const float v1[3], const float v2[3], const float v3[3], const float v4[3]);
 bool is_quad_convex_v2(const float v1[2], const float v2[2], const float v3[2], const float v4[2]);
 bool is_poly_convex_v2(const float verts[][2], unsigned int nr);
+/**
+ * Check if either of the diagonals along this quad create flipped triangles
+ * (normals pointing away from eachother).
+ * - (1 << 0): (v1-v3) is flipped.
+ * - (1 << 1): (v2-v4) is flipped.
+ */
 int is_quad_flip_v3(const float v1[3], const float v2[3], const float v3[3], const float v4[3]);
 bool is_quad_flip_v3_first_third_fast(const float v1[3],
                                       const float v2[3],
@@ -111,36 +171,88 @@ bool is_quad_flip_v3_first_third_fast_with_normal(const float v1[3],
                                                   const float v4[3],
                                                   const float normal[3]);
 
-/********************************* Distance **********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Distance
+ * \{ */
 
+/**
+ * Distance p to line v1-v2 using Hesse formula (NO LINE PIECE!)
+ */
 float dist_squared_to_line_v2(const float p[2], const float l1[2], const float l2[2]);
 float dist_to_line_v2(const float p[2], const float l1[2], const float l2[2]);
+/**
+ * Distance p to line-piece v1-v2.
+ */
 float dist_squared_to_line_segment_v2(const float p[2], const float l1[2], const float l2[2]);
 float dist_to_line_segment_v2(const float p[2], const float l1[2], const float l2[2]);
 
 float dist_signed_squared_to_plane_v3(const float p[3], const float plane[4]);
 float dist_squared_to_plane_v3(const float p[3], const float plane[4]);
+/**
+ * Return the signed distance from the point to the plane.
+ */
 float dist_signed_to_plane_v3(const float p[3], const float plane[4]);
 float dist_to_plane_v3(const float p[3], const float plane[4]);
 
-/* plane3 versions */
+/* Plane3 versions. */
+
 float dist_signed_squared_to_plane3_v3(const float p[3], const float plane[3]);
 float dist_squared_to_plane3_v3(const float p[3], const float plane[3]);
 float dist_signed_to_plane3_v3(const float p[3], const float plane[3]);
 float dist_to_plane3_v3(const float p[3], const float plane[3]);
 
+/**
+ * Distance v1 to line-piece l1-l2 in 3D.
+ */
 float dist_squared_to_line_segment_v3(const float p[3], const float l1[3], const float l2[3]);
 float dist_to_line_segment_v3(const float p[3], const float l1[3], const float l2[3]);
 float dist_squared_to_line_v3(const float p[3], const float l1[3], const float l2[3]);
 float dist_to_line_v3(const float p[3], const float l1[3], const float l2[3]);
+/**
+ * Check if \a p is inside the 2x planes defined by `(v1, v2, v3)`
+ * where the 3x points define 2x planes.
+ *
+ * \param axis_ref: used when v1,v2,v3 form a line and to check if the corner is concave/convex.
+ *
+ * \note the distance from \a v1 & \a v3 to \a v2 doesn't matter
+ * (it just defines the planes).
+ *
+ * \return the lowest squared distance to either of the planes.
+ * where `(return < 0.0)` is outside.
+ *
+ * <pre>
+ *            v1
+ *            +
+ *           /
+ * x - out  /  x - inside
+ *         /
+ *        +----+
+ *        v2   v3
+ *           x - also outside
+ * </pre>
+ */
 float dist_signed_squared_to_corner_v3v3v3(const float p[3],
                                            const float v1[3],
                                            const float v2[3],
                                            const float v3[3],
                                            const float axis_ref[3]);
+/**
+ * Compute the squared distance of a point to a line (defined as ray).
+ * \param ray_origin: A point on the line.
+ * \param ray_direction: Normalized direction of the line.
+ * \param co: Point to which the distance is to be calculated.
+ */
 float dist_squared_to_ray_v3_normalized(const float ray_origin[3],
                                         const float ray_direction[3],
                                         const float co[3]);
+/**
+ * Find the closest point in a seg to a ray and return the distance squared.
+ * \param r_point: Is the point on segment closest to ray
+ * (or to ray_origin if the ray and the segment are parallel).
+ * \param r_depth: the distance of r_point projection on ray to the ray_origin.
+ */
 float dist_squared_ray_to_seg_v3(const float ray_origin[3],
                                  const float ray_direction[3],
                                  const float v0[3],
@@ -148,6 +260,9 @@ float dist_squared_ray_to_seg_v3(const float ray_origin[3],
                                  float r_point[3],
                                  float *r_depth);
 
+/**
+ * Returns the coordinates of the nearest vertex and the farthest vertex from a plane (or normal).
+ */
 void aabb_get_near_far_from_plane(const float plane_no[3],
                                   const float bbmin[3],
                                   const float bbmax[3],
@@ -162,12 +277,17 @@ struct DistRayAABB_Precalc {
 void dist_squared_ray_to_aabb_v3_precalc(struct DistRayAABB_Precalc *neasrest_precalc,
                                          const float ray_origin[3],
                                          const float ray_direction[3]);
+/**
+ * Returns the distance from a ray to a bound-box (projected on ray)
+ */
 float dist_squared_ray_to_aabb_v3(const struct DistRayAABB_Precalc *data,
                                   const float bb_min[3],
                                   const float bb_max[3],
                                   float r_point[3],
                                   float *r_depth);
-/* when there is no advantage to precalc. */
+/**
+ * Use when there is no advantage to pre-calculation.
+ */
 float dist_squared_ray_to_aabb_v3_simple(const float ray_origin[3],
                                          const float ray_direction[3],
                                          const float bb_min[3],
@@ -182,10 +302,17 @@ struct DistProjectedAABBPrecalc {
   float pmat[4][4];
   float mval[2];
 };
+/**
+ * \param projmat: Projection Matrix (usually perspective
+ * matrix multiplied by object matrix).
+ */
 void dist_squared_to_projected_aabb_precalc(struct DistProjectedAABBPrecalc *precalc,
                                             const float projmat[4][4],
                                             const float winsize[2],
                                             const float mval[2]);
+/**
+ * Returns the distance from a 2D coordinate to a bound-box (projected).
+ */
 float dist_squared_to_projected_aabb(struct DistProjectedAABBPrecalc *data,
                                      const float bbmin[3],
                                      const float bbmax[3],
@@ -205,21 +332,42 @@ double closest_to_line_v2_db(double r_close[2],
                              const double p[2],
                              const double l1[2],
                              const double l2[2]);
+/**
+ * Find closest point to p on line through (l1, l2) and return lambda,
+ * where (0 <= lambda <= 1) when cp is in the line segment (l1, l2).
+ */
 float closest_to_line_v3(float r_close[3], const float p[3], const float l1[3], const float l2[3]);
+/**
+ * Point closest to v1 on line v2-v3 in 2D.
+ */
 void closest_to_line_segment_v2(float r_close[2],
                                 const float p[2],
                                 const float l1[2],
                                 const float l2[2]);
+/**
+ * Point closest to v1 on line v2-v3 in 3D.
+ */
 void closest_to_line_segment_v3(float r_close[3],
                                 const float p[3],
                                 const float l1[3],
                                 const float l2[3]);
 void closest_to_plane_normalized_v3(float r_close[3], const float plane[4], const float pt[3]);
+/**
+ * Find the closest point on a plane.
+ *
+ * \param r_close: Return coordinate
+ * \param plane: The plane to test against.
+ * \param pt: The point to find the nearest of
+ *
+ * \note non-unit-length planes are supported.
+ */
 void closest_to_plane_v3(float r_close[3], const float plane[4], const float pt[3]);
 void closest_to_plane3_normalized_v3(float r_close[3], const float plane[3], const float pt[3]);
 void closest_to_plane3_v3(float r_close[3], const float plane[3], const float pt[3]);
 
-/* Set 'r' to the point in triangle (v1, v2, v3) closest to point 'p' */
+/**
+ * Set 'r' to the point in triangle (v1, v2, v3) closest to point 'p'.
+ */
 void closest_on_tri_to_point_v3(
     float r[3], const float p[3], const float v1[3], const float v2[3], const float v3[3]);
 
@@ -232,6 +380,13 @@ float ray_point_factor_v3(const float p[3],
                           const float ray_origin[3],
                           const float ray_direction[3]);
 
+/**
+ * A simplified version of #closest_to_line_v3
+ * we only need to return the `lambda`
+ *
+ * \param epsilon: avoid approaching divide-by-zero.
+ * Passing a zero will just check for nonzero division.
+ */
 float line_point_factor_v3_ex(const float p[3],
                               const float l1[3],
                               const float l2[3],
@@ -246,14 +401,25 @@ float line_point_factor_v2_ex(const float p[2],
                               const float fallback);
 float line_point_factor_v2(const float p[2], const float l1[2], const float l2[2]);
 
+/**
+ * \note #isect_line_plane_v3() shares logic.
+ */
 float line_plane_factor_v3(const float plane_co[3],
                            const float plane_no[3],
                            const float l1[3],
                            const float l2[3]);
 
+/**
+ * Ensure the distance between these points is no greater than 'dist'.
+ * If it is, scale them both into the center.
+ */
 void limit_dist_v3(float v1[3], float v2[3], const float dist);
 
-/******************************* Intersection ********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Intersection
+ * \{ */
 
 /* TODO: int return value consistency. */
 
@@ -263,7 +429,13 @@ void limit_dist_v3(float v1[3], float v2[3], const float dist);
 #define ISECT_LINE_LINE_EXACT 1
 #define ISECT_LINE_LINE_CROSS 2
 
+/**
+ * Intersect Line-Line, floats.
+ */
 int isect_seg_seg_v2(const float v1[2], const float v2[2], const float v3[2], const float v4[2]);
+/**
+ * Returns a point on each segment that is closest to the other.
+ */
 void isect_seg_seg_v3(const float a0[3],
                       const float a1[3],
                       const float b0[3],
@@ -271,7 +443,21 @@ void isect_seg_seg_v3(const float a0[3],
                       float r_a[3],
                       float r_b[3]);
 
+/* intersect Line-Line, shorts */
 int isect_seg_seg_v2_int(const int v1[2], const int v2[2], const int v3[2], const int v4[2]);
+/**
+ * Get intersection point of two 2D segments.
+ *
+ * \param endpoint_bias: Bias to use when testing for end-point overlap.
+ * A positive value considers intersections that extend past the endpoints,
+ * negative values contract the endpoints.
+ * Note the bias is applied to a 0-1 factor, not scaled to the length of segments.
+ *
+ * \returns intersection type:
+ * - -1: collinear.
+ * -  1: intersection.
+ * -  0: no intersection.
+ */
 int isect_seg_seg_v2_point_ex(const float v0[2],
                               const float v1[2],
                               const float v2[2],
@@ -284,12 +470,37 @@ bool isect_seg_seg_v2_simple(const float v1[2],
                              const float v2[2],
                              const float v3[2],
                              const float v4[2]);
+/**
+ * If intersection == ISECT_LINE_LINE_CROSS or ISECT_LINE_LINE_NONE:
+ * <pre>
+ * pt = v1 + lambda * (v2 - v1) = v3 + mu * (v4 - v3)
+ * </pre>
+ * \returns intersection type:
+ * - ISECT_LINE_LINE_COLINEAR: collinear.
+ * - ISECT_LINE_LINE_EXACT: intersection at an endpoint of either.
+ * - ISECT_LINE_LINE_CROSS: interaction, not at an endpoint.
+ * - ISECT_LINE_LINE_NONE: no intersection.
+ * Also returns lambda and mu in r_lambda and r_mu.
+ */
 int isect_seg_seg_v2_lambda_mu_db(const double v1[2],
                                   const double v2[2],
                                   const double v3[2],
                                   const double v4[2],
                                   double *r_lambda,
                                   double *r_mu);
+/**
+ * \param l1, l2: Coordinates (point of line).
+ * \param sp, r: Coordinate and radius (sphere).
+ * \return r_p1, r_p2: Intersection coordinates.
+ *
+ * \note The order of assignment for intersection points (\a r_p1, \a r_p2) is predictable,
+ * based on the direction defined by `l2 - l1`,
+ * this direction compared with the normal of each point on the sphere:
+ * \a r_p1 always has a >= 0.0 dot product.
+ * \a r_p2 always has a <= 0.0 dot product.
+ * For example, when \a l1 is inside the sphere and \a l2 is outside,
+ * \a r_p1 will always be between \a l1 and \a l2.
+ */
 int isect_line_sphere_v3(const float l1[3],
                          const float l2[3],
                          const float sp[3],
@@ -303,8 +514,17 @@ int isect_line_sphere_v2(const float l1[2],
                          float r_p1[2],
                          float r_p2[2]);
 
+/**
+ * Intersect Line-Line, floats - gives intersection point.
+ */
 int isect_line_line_v2_point(
     const float v0[2], const float v1[2], const float v2[2], const float v3[2], float r_vi[2]);
+/**
+ * \return The number of point of interests
+ * 0 - lines are collinear
+ * 1 - lines are coplanar, i1 is set to intersection
+ * 2 - i1 and i2 are the nearest points on line 1 (v1, v2) and line 2 (v3, v4) respectively
+ */
 int isect_line_line_epsilon_v3(const float v1[3],
                                const float v2[3],
                                const float v3[3],
@@ -318,12 +538,22 @@ int isect_line_line_v3(const float v1[3],
                        const float v4[3],
                        float r_i1[3],
                        float r_i2[3]);
+/**
+ * Intersection point strictly between the two lines
+ * \return false when no intersection is found.
+ */
 bool isect_line_line_strict_v3(const float v1[3],
                                const float v2[3],
                                const float v3[3],
                                const float v4[3],
                                float vi[3],
                                float *r_lambda);
+/**
+ * Check if two rays are not parallel and returns a factor that indicates
+ * the distance from \a ray_origin_b to the closest point on ray-a to ray-b.
+ *
+ * \note Neither directions need to be normalized.
+ */
 bool isect_ray_ray_epsilon_v3(const float ray_origin_a[3],
                               const float ray_direction_a[3],
                               const float ray_origin_b[3],
@@ -338,30 +568,85 @@ bool isect_ray_ray_v3(const float ray_origin_a[3],
                       float *r_lambda_a,
                       float *r_lambda_b);
 
+/**
+ * if clip is nonzero, will only return true if lambda is >= 0.0
+ * (i.e. intersection point is along positive \a ray_direction)
+ *
+ * \note #line_plane_factor_v3() shares logic.
+ */
 bool isect_ray_plane_v3(const float ray_origin[3],
                         const float ray_direction[3],
                         const float plane[4],
                         float *r_lambda,
                         const bool clip);
 
+/**
+ * Check if a point is behind all planes.
+ */
 bool isect_point_planes_v3(float (*planes)[4], int totplane, const float p[3]);
+/**
+ * Check if a point is in front all planes.
+ * Same as isect_point_planes_v3 but with planes facing the opposite direction.
+ */
 bool isect_point_planes_v3_negated(const float (*planes)[4], const int totplane, const float p[3]);
 
+/**
+ * Intersect line/plane.
+ *
+ * \param r_isect_co: The intersection point.
+ * \param l1: The first point of the line.
+ * \param l2: The second point of the line.
+ * \param plane_co: A point on the plane to intersect with.
+ * \param plane_no: The direction of the plane (does not need to be normalized).
+ *
+ * \note #line_plane_factor_v3() shares logic.
+ */
 bool isect_line_plane_v3(float r_isect_co[3],
                          const float l1[3],
                          const float l2[3],
                          const float plane_co[3],
                          const float plane_no[3]) ATTR_WARN_UNUSED_RESULT;
 
+/**
+ * Intersect three planes, return the point where all 3 meet.
+ * See Graphics Gems 1 pg 305
+ *
+ * \param plane_a, plane_b, plane_c: Planes.
+ * \param r_isect_co: The resulting intersection point.
+ */
 bool isect_plane_plane_plane_v3(const float plane_a[4],
                                 const float plane_b[4],
                                 const float plane_c[4],
                                 float r_isect_co[3]) ATTR_WARN_UNUSED_RESULT;
+/**
+ * Intersect two planes, return a point on the intersection and a vector
+ * that runs on the direction of the intersection.
+ * \note this is a slightly reduced version of #isect_plane_plane_plane_v3
+ *
+ * \param plane_a, plane_b: Planes.
+ * \param r_isect_co: The resulting intersection point.
+ * \param r_isect_no: The resulting vector of the intersection.
+ *
+ * \note \a r_isect_no isn't unit length.
+ */
 bool isect_plane_plane_v3(const float plane_a[4],
                           const float plane_b[4],
                           float r_isect_co[3],
                           float r_isect_no[3]) ATTR_WARN_UNUSED_RESULT;
 
+/**
+ * Intersect all planes, calling `callback_fn` for each point that intersects
+ * 3 of the planes that isn't outside any of the other planes.
+ *
+ * This can be thought of as calculating a convex-hull from an array of planes.
+ *
+ * \param eps_coplanar: Epsilon for testing if two planes are aligned (co-planar).
+ * \param eps_isect: Epsilon for testing of a point is behind any of the planes.
+ *
+ * \warning As complexity is a little under `O(N^3)`, this is only suitable for small arrays.
+ *
+ * \note This function could be optimized by some spatial structure.
+ */
 bool isect_planes_v3_fn(
     const float planes[][4],
     const int planes_len,
@@ -371,6 +656,11 @@ bool isect_planes_v3_fn(
     void *user_data);
 
 /* line/ray triangle */
+
+/**
+ * Test if the line starting at p1 ending at p2 intersects the triangle v0..v2
+ * return non zero if it does.
+ */
 bool isect_line_segment_tri_v3(const float p1[3],
                                const float p2[3],
                                const float v0[3],
@@ -378,6 +668,9 @@ bool isect_line_segment_tri_v3(const float p1[3],
                                const float v2[3],
                                float *r_lambda,
                                float r_uv[2]);
+/**
+ * Like #isect_line_segment_tri_v3, but allows epsilon tolerance around triangle.
+ */
 bool isect_line_segment_tri_epsilon_v3(const float p1[3],
                                        const float p2[3],
                                        const float v0[3],
@@ -394,6 +687,10 @@ bool isect_axial_line_segment_tri_v3(const int axis,
                                      const float v2[3],
                                      float *r_lambda);
 
+/**
+ * Test if the ray starting at p1 going in d direction intersects the triangle v0..v2
+ * return non zero if it does.
+ */
 bool isect_ray_tri_v3(const float ray_origin[3],
                       const float ray_direction[3],
                       const float v0[3],
@@ -417,6 +714,16 @@ bool isect_ray_tri_epsilon_v3(const float ray_origin[3],
                               float *r_lambda,
                               float r_uv[2],
                               const float epsilon);
+/**
+ * Intersect two triangles.
+ *
+ * \param r_i1, r_i2: Retrieve the overlapping edge between the 2 triangles.
+ * \param r_tri_a_edge_isect_count: Indicates how many edges in the first triangle are intersected.
+ * \return true when the triangles intersect.
+ *
+ * \note If it exists, \a r_i1 will be a point on the edge of the 1st triangle.
+ * \note intersections between coplanar triangles are currently undetected.
+ */
 bool isect_tri_tri_v3_ex(const float tri_a[3][3],
                          const float tri_b[3][3],
                          float r_i1[3],
@@ -438,7 +745,9 @@ bool isect_tri_tri_v2(const float p1[2],
                       const float q2[2],
                       const float r2[2]);
 
-/* water-tight ray-cast (requires pre-calculation). */
+/**
+ * Water-tight ray-cast (requires pre-calculation).
+ */
 struct IsectRayPrecalc {
   /* Maximal dimension `kz`, and orthogonal dimensions. */
   int kx, ky, kz;
@@ -456,7 +765,9 @@ bool isect_ray_tri_watertight_v3(const float ray_origin[3],
                                  const float v2[3],
                                  float *r_dist,
                                  float r_uv[2]);
-/* slower version which calculates IsectRayPrecalc each time */
+/**
+ * Slower version which calculates #IsectRayPrecalc each time.
+ */
 bool isect_ray_tri_watertight_v3_simple(const float ray_origin[3],
                                         const float ray_direction[3],
                                         const float v0[3],
@@ -478,7 +789,8 @@ bool isect_ray_line_v3(const float ray_origin[3],
                        const float v1[3],
                        float *r_lambda);
 
-/* point in polygon */
+/* Point in polygon. */
+
 bool isect_point_poly_v2(const float pt[2],
                          const float verts[][2],
                          const unsigned int nr,
@@ -488,27 +800,50 @@ bool isect_point_poly_v2_int(const int pt[2],
                              const unsigned int nr,
                              const bool use_holes);
 
+/**
+ * Point in quad - only convex quads.
+ */
 int isect_point_quad_v2(
     const float p[2], const float v1[2], const float v2[2], const float v3[2], const float v4[2]);
 
 int isect_point_tri_v2(const float pt[2], const float v1[2], const float v2[2], const float v3[2]);
+/**
+ * Only single direction.
+ */
 bool isect_point_tri_v2_cw(const float pt[2],
                            const float v1[2],
                            const float v2[2],
                            const float v3[2]);
+/**
+ * \code{.unparsed}
+ * x1,y2
+ * |  \
+ * |   \     .(a,b)
+ * |    \
+ * x1,y1-- x2,y1
+ * \endcode
+ */
 int isect_point_tri_v2_int(
     const int x1, const int y1, const int x2, const int y2, const int a, const int b);
 bool isect_point_tri_prism_v3(const float p[3],
                               const float v1[3],
                               const float v2[3],
                               const float v3[3]);
+/**
+ * \param r_isect_co: The point \a p projected onto the triangle.
+ * \return True when \a p is inside the triangle.
+ * \note Its up to the caller to check the distance between \a p and \a r_vi
+ * against an error margin.
+ */
 bool isect_point_tri_v3(const float p[3],
                         const float v1[3],
                         const float v2[3],
                         const float v3[3],
                         float r_isect_co[3]);
 
-/* axis-aligned bounding box */
+/**
+ * Axis-aligned bounding box.
+ */
 bool isect_aabb_aabb_v3(const float min1[3],
                         const float max1[3],
                         const float min2[3],
@@ -527,6 +862,13 @@ bool isect_ray_aabb_v3(const struct IsectRayAABB_Precalc *data,
                        const float bb_min[3],
                        const float bb_max[3],
                        float *tmin);
+/**
+ * Test a bounding box (AABB) for ray intersection.
+ * Assumes the ray is already local to the boundbox space.
+ *
+ * \note \a direction should be normalized
+ * if you intend to use the \a tmin or \a tmax distance results!
+ */
 bool isect_ray_aabb_v3_simple(const float orig[3],
                               const float dir[3],
                               const float bb_min[3],
@@ -539,6 +881,14 @@ bool isect_ray_aabb_v3_simple(const float orig[3],
 #define ISECT_AABB_PLANE_CROSS_ANY 1
 #define ISECT_AABB_PLANE_IN_FRONT_ALL 2
 
+/**
+ * Checks status of an AABB in relation to a list of planes.
+ *
+ * \returns intersection type:
+ * - ISECT_AABB_PLANE_BEHIND_ONE   (0): AABB is completely behind at least 1 plane;
+ * - ISECT_AABB_PLANE_CROSS_ANY    (1): AABB intersects at least 1 plane;
+ * - ISECT_AABB_PLANE_IN_FRONT_ALL (2): AABB is completely in front of all planes;
+ */
 int isect_aabb_planes_v3(const float (*planes)[4],
                          const int totplane,
                          const float bbmin[3],
@@ -564,7 +914,12 @@ bool clip_segment_v3_plane_n(const float p1[3],
 
 bool point_in_slice_seg(float p[3], float l1[3], float l2[3]);
 
-/****************************** Interpolation ********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Interpolation
+ * \{ */
+
 void interp_weights_tri_v3(
     float w[3], const float v1[3], const float v2[3], const float v3[3], const float co[3]);
 void interp_weights_quad_v3(float w[4],
@@ -576,6 +931,7 @@ void interp_weights_quad_v3(float w[4],
 void interp_weights_poly_v3(float w[], float v[][3], const int n, const float co[3]);
 void interp_weights_poly_v2(float w[], float v[][2], const int n, const float co[2]);
 
+/* (x1, v1)(t1=0)------(x2, v2)(t2=1), 0<t<1 --> (x, v)(t) */
 void interp_cubic_v3(float x[3],
                      float v[3],
                      const float x1[3],
@@ -584,8 +940,17 @@ void interp_cubic_v3(float x[3],
                      const float v2[3],
                      const float t);
 
+/**
+ * Given an array with some invalid values this function interpolates valid values
+ * replacing the invalid ones.
+ */
 int interp_sparse_array(float *array, const int list_size, const float skipval);
 
+/**
+ * Given 2 triangles in 3D space, and a point in relation to the first triangle.
+ * calculate the location of a point in relation to the second triangle.
+ * Useful for finding relative positions with geometry.
+ */
 void transform_point_by_tri_v3(float pt_tar[3],
                                float const pt_src[3],
                                const float tri_tar_p1[3],
@@ -594,6 +959,10 @@ void transform_point_by_tri_v3(float pt_tar[3],
                                const float tri_src_p1[3],
                                const float tri_src_p2[3],
                                const float tri_src_p3[3]);
+/**
+ * Simply re-interpolates,
+ * assumes p_src is between \a l_src_p1-l_src_p2
+ */
 void transform_point_by_seg_v3(float p_dst[3],
                                const float p_src[3],
                                const float l_dst_p1[3],
@@ -601,12 +970,32 @@ void transform_point_by_seg_v3(float p_dst[3],
                                const float l_src_p1[3],
                                const float l_src_p2[3]);
 
+/**
+ * \note Using #cross_tri_v2 means locations outside the triangle are correctly weighted.
+ *
+ * \note This is *exactly* the same calculation as #resolve_tri_uv_v2,
+ * although it has double precision and is used for texture baking, so keep both.
+ */
 void barycentric_weights_v2(
     const float v1[2], const float v2[2], const float v3[2], const float co[2], float w[3]);
+/**
+ * A version of #barycentric_weights_v2 that doesn't allow negative weights.
+ * Useful when negative values cause problems and points are only
+ * ever slightly outside of the triangle.
+ */
 void barycentric_weights_v2_clamped(
     const float v1[2], const float v2[2], const float v3[2], const float co[2], float w[3]);
+/**
+ * still use 2D X,Y space but this works for verts transformed by a perspective matrix,
+ * using their 4th component as a weight
+ */
 void barycentric_weights_v2_persp(
     const float v1[4], const float v2[4], const float v3[4], const float co[2], float w[3]);
+/**
+ * same as #barycentric_weights_v2 but works with a quad,
+ * NOTE: untested for values outside the quad's bounds
+ * this is #interp_weights_poly_v2 expanded for quads only
+ */
 void barycentric_weights_v2_quad(const float v1[2],
                                  const float v2[2],
                                  const float v3[2],
@@ -614,20 +1003,47 @@ void barycentric_weights_v2_quad(const float v1[2],
                                  const float co[2],
                                  float w[4]);
 
+/**
+ * \return false for degenerated triangles.
+ */
 bool barycentric_coords_v2(
     const float v1[2], const float v2[2], const float v3[2], const float co[2], float w[3]);
+/**
+ * \return
+ * - 0 if the point is outside of triangle.
+ * - 1 if the point is inside triangle.
+ * - 2 if it's on the edge.
+ */
 int barycentric_inside_triangle_v2(const float w[3]);
 
+/**
+ * Barycentric reverse
+ *
+ * Compute coordinates (u, v) for point \a st with respect to triangle (\a st0, \a st1, \a st2)
+ *
+ * \note same basic result as #barycentric_weights_v2, see its comment for details.
+ */
 void resolve_tri_uv_v2(
     float r_uv[2], const float st[2], const float st0[2], const float st1[2], const float st2[2]);
+/**
+ * Barycentric reverse 3d
+ *
+ * Compute coordinates (u, v) for point \a st with respect to triangle (\a st0, \a st1, \a st2)
+ */
 void resolve_tri_uv_v3(
     float r_uv[2], const float st[3], const float st0[3], const float st1[3], const float st2[3]);
+/**
+ * Bilinear reverse.
+ */
 void resolve_quad_uv_v2(float r_uv[2],
                         const float st[2],
                         const float st0[2],
                         const float st1[2],
                         const float st2[2],
                         const float st3[2]);
+/**
+ * Bilinear reverse with derivatives.
+ */
 void resolve_quad_uv_v2_deriv(float r_uv[2],
                               float r_deriv[2][2],
                               const float st[2],
@@ -635,22 +1051,35 @@ void resolve_quad_uv_v2_deriv(float r_uv[2],
                               const float st1[2],
                               const float st2[2],
                               const float st3[2]);
+/**
+ * A version of resolve_quad_uv_v2 that only calculates the 'u'.
+ */
 float resolve_quad_u_v2(const float st[2],
                         const float st0[2],
                         const float st1[2],
                         const float st2[2],
                         const float st3[2]);
 
-/* use to find the point of a UV on a face */
+/**
+ * Use to find the point of a UV on a face.
+ * Reverse of `resolve_*` functions.
+ */
 void interp_bilinear_quad_v3(float data[4][3], float u, float v, float res[3]);
 void interp_barycentric_tri_v3(float data[3][3], float u, float v, float res[3]);
 
-/***************************** View & Projection *****************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name View & Projection
+ * \{ */
 
 void lookat_m4(
     float mat[4][4], float vx, float vy, float vz, float px, float py, float pz, float twist);
 void polarview_m4(float mat[4][4], float dist, float azimuth, float incidence, float twist);
 
+/**
+ * Matches `glFrustum` result.
+ */
 void perspective_m4(float mat[4][4],
                     const float left,
                     const float right,
@@ -665,6 +1094,9 @@ void perspective_m4_fov(float mat[4][4],
                         const float angle_down,
                         const float nearClip,
                         const float farClip);
+/**
+ * Matches `glOrtho` result.
+ */
 void orthographic_m4(float mat[4][4],
                      const float left,
                      const float right,
@@ -672,8 +1104,18 @@ void orthographic_m4(float mat[4][4],
                      const float top,
                      const float nearClip,
                      const float farClip);
+/**
+ * Translate a matrix created by orthographic_m4 or perspective_m4 in XY coords
+ * (used to jitter the view).
+ */
 void window_translate_m4(float winmat[4][4], float perspmat[4][4], const float x, const float y);
 
+/**
+ * Frustum planes extraction from a projection matrix
+ * (homogeneous 4d vector representations of planes).
+ *
+ * plane parameters can be NULL if you do not need them.
+ */
 void planes_from_projmat(const float mat[4][4],
                          float left[4],
                          float right[4],
@@ -697,6 +1139,14 @@ void projmat_dimensions_db(const float winmat[4][4],
                            double *r_near,
                            double *r_far);
 
+/**
+ * Creates a projection matrix for a small region of the viewport.
+ *
+ * \param projmat: Projection Matrix.
+ * \param win_size: Viewport Size.
+ * \param x_min, x_max, y_min, y_max: Coordinates of the subregion.
+ * \return r_projmat: Resulting Projection Matrix.
+ */
 void projmat_from_subregion(const float projmat[4][4],
                             const int win_size[2],
                             const int x_min,
@@ -708,7 +1158,11 @@ void projmat_from_subregion(const float projmat[4][4],
 int box_clip_bounds_m4(float boundbox[2][3], const float bounds[4], float winmat[4][4]);
 void box_minmax_bounds_m4(float min[3], float max[3], float boundbox[2][3], float mat[4][4]);
 
-/********************************** Mapping **********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Mapping
+ * \{ */
 
 void map_to_tube(float *r_u, float *r_v, const float x, const float y, const float z);
 void map_to_sphere(float *r_u, float *r_v, const float x, const float y, const float z);
@@ -718,7 +1172,11 @@ void map_to_plane_axis_angle_v2_v3v3fl(float r_co[2],
                                        const float axis[3],
                                        const float angle);
 
-/********************************** Normals **********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Normals
+ * \{ */
 
 void accumulate_vertex_normals_tri_v3(float n1[3],
                                       float n2[3],
@@ -738,13 +1196,21 @@ void accumulate_vertex_normals_v3(float n1[3],
                                   const float co3[3],
                                   const float co4[3]);
 
+/**
+ * Add weighted face normal component into normals of the face vertices.
+ * Caller must pass pre-allocated vdiffs of nverts length.
+ */
 void accumulate_vertex_normals_poly_v3(float **vertnos,
                                        const float polyno[3],
                                        const float **vertcos,
                                        float vdiffs[][3],
                                        const int nverts);
 
-/********************************* Tangents **********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Tangents
+ * \{ */
 
 void tangent_from_uv_v3(const float uv1[2],
                         const float uv2[2],
@@ -755,8 +1221,31 @@ void tangent_from_uv_v3(const float uv1[2],
                         const float n[3],
                         float r_tang[3]);
 
-/******************************** Vector Clouds ******************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Vector Clouds
+ * \{ */
 
+/**
+ * Input:
+ *
+ * \param list_size: 4 lists as pointer to array[list_size]
+ * \param pos: current pos array of 'new' positions
+ * \param weight: current weight array of 'new'weights (may be NULL pointer if you have no weights)
+ * \param rpos: Reference rpos array of 'old' positions
+ * \param rweight: Reference rweight array of 'old'weights
+ * (may be NULL pointer if you have no weights).
+ *
+ * Output:
+ *
+ * \param lloc: Center of mass pos.
+ * \param rloc: Center of mass rpos.
+ * \param lrot: Rotation matrix.
+ * \param lscale: Scale matrix.
+ *
+ * pointers may be NULL if not needed
+ */
 void vcloud_estimate_transform_v3(const int list_size,
                                   const float (*pos)[3],
                                   const float *weight,
@@ -767,12 +1256,16 @@ void vcloud_estimate_transform_v3(const int list_size,
                                   float lrot[3][3],
                                   float lscale[3][3]);
 
-/****************************** Spherical Harmonics *************************/
+/** \} */
 
-/* Uses 2nd order SH => 9 coefficients, stored in this order:
- * 0 = (0, 0),
- * 1 = (1, -1), 2 = (1, 0), 3 = (1, 1),
- * 4 = (2, -2), 5 = (2, -1), 6 = (2, 0), 7 = (2, 1), 8 = (2, 2) */
+/* -------------------------------------------------------------------- */
+/** \name Spherical Harmonics
+ *
+ * Uses 2nd order SH => 9 coefficients, stored in this order:
+ * - 0 = `(0, 0)`
+ * - 1 = `(1, -1), 2 = (1, 0), 3 = (1, 1)`
+ * - 4 = `(2, -2), 5 = (2, -1), 6 = (2, 0), 7 = (2, 1), 8 = (2, 2)`
+ * \{ */
 
 MINLINE void zero_sh(float r[9]);
 MINLINE void copy_sh_sh(float r[9], const float a[9]);
@@ -785,7 +1278,11 @@ MINLINE float diffuse_shv3(const float r[9], const float v[3]);
 MINLINE void vec_fac_to_sh(float r[9], const float v[3], const float f);
 MINLINE void madd_sh_shfl(float r[9], const float sh[9], const float f);
 
-/********************************* Form Factor *******************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Form Factor
+ * \{ */
 
 float form_factor_quad(const float p[3],
                        const float n[3],
@@ -805,37 +1302,117 @@ bool form_factor_visible_quad(const float p[3],
 float form_factor_hemi_poly(
     float p[3], float n[3], float v1[3], float v2[3], float v3[3], float v4[3]);
 
+/**
+ * Same as axis_dominant_v3_to_m3, but flips the normal
+ */
 void axis_dominant_v3_to_m3_negate(float r_mat[3][3], const float normal[3]);
+/**
+ * \brief Normal to x,y matrix
+ *
+ * Creates a 3x3 matrix from a normal.
+ * This matrix can be applied to vectors so their 'z' axis runs along \a normal.
+ * In practice it means you can use x,y as 2d coords. \see
+ *
+ * \param r_mat: The matrix to return.
+ * \param normal: A unit length vector.
+ */
 void axis_dominant_v3_to_m3(float r_mat[3][3], const float normal[3]);
 
+/**
+ * Get the 2 dominant axis values, 0==X, 1==Y, 2==Z.
+ */
 MINLINE void axis_dominant_v3(int *r_axis_a, int *r_axis_b, const float axis[3]);
+/**
+ * Same as #axis_dominant_v3 but return the max value.
+ */
 MINLINE float axis_dominant_v3_max(int *r_axis_a,
                                    int *r_axis_b,
                                    const float axis[3]) ATTR_WARN_UNUSED_RESULT;
+/**
+ * Get the single dominant axis value, 0==X, 1==Y, 2==Z.
+ */
 MINLINE int axis_dominant_v3_single(const float vec[3]);
+/**
+ * The dominant axis of an orthogonal vector.
+ */
 MINLINE int axis_dominant_v3_ortho_single(const float vec[3]);
 
 MINLINE int max_axis_v3(const float vec[3]);
 MINLINE int min_axis_v3(const float vec[3]);
 
+/**
+ * Simple function to either:
+ * - Calculate how many triangles needed from the total number of polygons + loops.
+ * - Calculate the first triangle index from the polygon index & that polygons loop-start.
+ *
+ * \param poly_count: The number of polygons or polygon-index
+ * (3+ sided faces, 1-2 sided give incorrect results).
+ * \param corner_count: The number of corners (also called loop-index).
+ */
 MINLINE int poly_to_tri_count(const int poly_count, const int corner_count);
 
+/**
+ * Useful to calculate an even width shell, by taking the angle between 2 planes.
+ * The return value is a scale on the offset.
+ * no angle between planes is 1.0, as the angle between the 2 planes approaches 180d
+ * the distance gets very high, 180d would be inf, but this case isn't valid.
+ */
 MINLINE float shell_angle_to_dist(const float angle);
+/**
+ * Equivalent to `shell_angle_to_dist(angle_normalized_v3v3(a, b))`.
+ */
 MINLINE float shell_v3v3_normalized_to_dist(const float a[3], const float b[3]);
+/**
+ * Equivalent to `shell_angle_to_dist(angle_normalized_v2v2(a, b))`.
+ */
 MINLINE float shell_v2v2_normalized_to_dist(const float a[2], const float b[2]);
+/**
+ * Equivalent to `shell_angle_to_dist(angle_normalized_v3v3(a, b) / 2)`.
+ */
 MINLINE float shell_v3v3_mid_normalized_to_dist(const float a[3], const float b[3]);
+/**
+ * Equivalent to `shell_angle_to_dist(angle_normalized_v2v2(a, b) / 2)`.
+ */
 MINLINE float shell_v2v2_mid_normalized_to_dist(const float a[2], const float b[2]);
 
-/********************************* Cubic (Bezier) *******************************/
+/** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Cubic (Bezier)
+ * \{ */
+
+/**
+ * Return the value which the distance between points will need to be scaled by,
+ * to define a handle, given both points are on a perfect circle.
+ *
+ * Use when we want a bezier curve to match a circle as closely as possible.
+ *
+ * \note the return value will need to be divided by 0.75 for correct results.
+ */
 float cubic_tangent_factor_circle_v3(const float tan_l[3], const float tan_r[3]);
 
-/********************************** Geodesics *********************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Geodesics
+ * \{ */
 
+/**
+ * Utility for computing approximate geodesic distances on triangle meshes.
+ *
+ * Given triangle with vertex coordinates v0, v1, v2, and known geodesic distances
+ * dist1 and dist2 at v1 and v2, estimate a geodesic distance at vertex v0.
+ *
+ * From "Dart Throwing on Surfaces", EGSR 2009. Section 7, Geodesic Dart Throwing.
+ */
 float geodesic_distance_propagate_across_triangle(
     const float v0[3], const float v1[3], const float v2[3], const float dist1, const float dist2);
 
-/**************************** Inline Definitions ******************************/
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Inline Definitions
+ * \{ */
 
 #if BLI_MATH_DO_INLINE
 #  include "intern/math_geom_inline.c"
@@ -845,6 +1422,8 @@ float geodesic_distance_propagate_across_triangle(
 #  pragma GCC diagnostic pop
 #endif
 
+/** \} */
+
 #ifdef __cplusplus
 }
 #endif