BLI Math: Add and use new `projmat_dimensions` utility.

2 files changed, 31 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_geom.h b/source/blender/blenlib/BLI_math_geom.h
index 4d095ab1900..2f81fbf37f6 100644
--- a/source/blender/blenlib/BLI_math_geom.h
+++ b/source/blender/blenlib/BLI_math_geom.h
@@ -441,6 +441,11 @@ void window_translate_m4(float winmat[4][4], float perspmat[4][4],
 void planes_from_projmat(float mat[4][4], float left[4], float right[4], float top[4], float bottom[4],
                          float front[4], float back[4]);
 
+void projmat_dimensions(const float projmat[4][4],
+                        float *r_left, float *r_right,
+                        float *r_bottom, float *r_top,
+                        float *r_near, float *r_far);
+
 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],
diff --git a/source/blender/blenlib/intern/math_geom.c b/source/blender/blenlib/intern/math_geom.c
index a513aca8e46..619a73f712f 100644
--- a/source/blender/blenlib/intern/math_geom.c
+++ b/source/blender/blenlib/intern/math_geom.c
@@ -4152,6 +4152,32 @@ void planes_from_projmat(float mat[4][4], float left[4], float right[4], float t
 	}
 }
 
+void projmat_dimensions(const float projmat[4][4],
+                        float *r_left, float *r_right,
+                        float *r_bottom, float *r_top,
+                        float *r_near, float *r_far)
+{
+	bool is_persp = projmat[3][3] == 0.0f;
+
+	if (is_persp) {
+		*r_left   = (projmat[2][0] - 1.0f) / projmat[0][0];
+		*r_right  = (projmat[2][0] + 1.0f) / projmat[0][0];
+		*r_bottom = (projmat[2][1] - 1.0f) / projmat[1][1];
+		*r_top    = (projmat[2][1] + 1.0f) / projmat[1][1];
+		*r_near   = projmat[3][2] / (projmat[2][2] - 1.0f);
+		*r_far    = projmat[3][2] / (projmat[2][2] + 1.0f);
+	}
+	else {
+		*r_left   = (-projmat[3][0] - 1.0f) / projmat[0][0];
+		*r_right  = (-projmat[3][0] + 1.0f) / projmat[0][0];
+		*r_bottom = (-projmat[3][1] - 1.0f) / projmat[1][1];
+		*r_top    = (-projmat[3][1] + 1.0f) / projmat[1][1];
+		*r_near   = ( projmat[3][2] + 1.0f) / projmat[2][2];
+		*r_far    = ( projmat[3][2] - 1.0f) / projmat[2][2];
+	}
+
+}
+
 static void i_multmatrix(float icand[4][4], float Vm[4][4])
 {
 	int row, col;