Cleanup: DRW: Renaming of glsl utility macros

1 files changed, 31 insertions, 8 deletions

diff --git a/source/blender/draw/modes/shaders/common_view_lib.glsl b/source/blender/draw/modes/shaders/common_view_lib.glsl
index 50d6760cafa..40c43856b43 100644
--- a/source/blender/draw/modes/shaders/common_view_lib.glsl
+++ b/source/blender/draw/modes/shaders/common_view_lib.glsl
@@ -14,11 +14,34 @@ layout(std140) uniform viewBlock
   vec4 clipPlanes[2];
 };
 
-/* Transform shortcuts. */
-#define transform_normal_object_to_world(nor) (transpose(mat3(ModelMatrixInverse)) * nor)
-#define transform_normal_world_to_object(nor) (transpose(mat3(ModelMatrix)) * nor)
-#define transform_normal_world_to_view(nor) (transpose(mat3(ViewMatrixInverse)) * nor)
-#define transform_normal_object_to_view(nor) \
-  (transpose(mat3(ViewMatrixInverse)) * (transpose(mat3(ModelMatrixInverse)) * nor))
-#define transform_point_view_to_object(point) \
-  ((ModelMatrixInverse * (ViewMatrixInverse * vec4(point, 1.0))).xyz)
+  /** Transform shortcuts. */
+  /* Rule of thumb: Try to reuse world positions and normals because converting though viewspace
+   * will always be decomposed in at least 2 matrix operation. */
+
+  /**
+   * Some clarification:
+   * Usually Normal matrix is transpose(inverse(ViewMatrix * ModelMatrix))
+   *
+   * But since it is slow to multiply matrices we decompose it. Decomposing
+   * inversion and transposition both invert the product order leaving us with
+   * the same original order:
+   * transpose(ViewMatrixInverse) * transpose(ModelMatrixInverse)
+   *
+   * Knowing that the view matrix is orthogonal, the transpose is also the inverse.
+   * Note: This is only valid because we are only using the mat3 of the ViewMatrixInverse.
+   * ViewMatrix * transpose(ModelMatrixInverse)
+   **/
+#define normal_object_to_view(nor) (mat3(ViewMatrix) * normal_object_to_world(nor))
+#define normal_object_to_world(nor) (transpose(mat3(ModelMatrixInverse)) * nor)
+#define normal_world_to_object(nor) (transpose(mat3(ModelMatrix)) * nor)
+#define normal_world_to_view(nor) (mat3(ViewMatrix) * nor)
+
+#define point_object_to_ndc(point) (ViewProjectionMatrix * (ModelMatrix * vec4(pt, 1.0)))
+#define point_object_to_view(point) ((ViewMatrix * (ModelMatrix * vec4(pt, 1.0))).xyz)
+#define point_object_to_world(point) ((ModelMatrix * vec4(point, 1.0)).xyz)
+#define point_view_to_ndc(point) (ProjectionMatrix * vec4(point, 1.0))
+#define point_view_to_object(point) ((ModelMatrixInverse * (ViewMatrixInverse * vec4(pt, 1.))).xyz)
+#define point_view_to_world(point) ((ViewMatrixInverse * vec4(point, 1.0)).xyz)
+#define point_world_to_ndc(point) (ViewProjectionMatrix * vec4(point, 1.0))
+#define point_world_to_object(point) ((ModelMatrixInverse * vec4(point, 1.0)).xyz)
+#define point_world_to_view(point) ((ViewMatrix * vec4(point, 1.0)).xyz)