Fix T57891: Radius of strip hair doesn't scale with object scale

Note that this only works fine with uniformly scaled objects.
Otherwise, the hair thickness will vary in a weird way depending on viewing
angles.

1 files changed, 6 insertions, 2 deletions

diff --git a/source/blender/draw/modes/shaders/common_hair_lib.glsl b/source/blender/draw/modes/shaders/common_hair_lib.glsl
index e272db02318..c0c5f84d166 100644
--- a/source/blender/draw/modes/shaders/common_hair_lib.glsl
+++ b/source/blender/draw/modes/shaders/common_hair_lib.glsl
@@ -135,7 +135,7 @@ float hair_shaperadius(float shape, float root, float tip, float time)
 }
 
 void hair_get_pos_tan_binor_time(
-        bool is_persp, vec3 camera_pos, vec3 camera_z,
+        bool is_persp, mat4 invmodel_mat, vec3 camera_pos, vec3 camera_z,
         out vec3 wpos, out vec3 wtan, out vec3 wbinor, out float time, out float thickness, out float thick_time)
 {
 	int id = hair_get_base_id();
@@ -159,7 +159,11 @@ void hair_get_pos_tan_binor_time(
 		thick_time = float(gl_VertexID % hairThicknessRes) / float(hairThicknessRes - 1);
 		thick_time = thickness * (thick_time * 2.0 - 1.0);
 
-		wpos += wbinor * thick_time;
+		/* Take object scale into account.
+		 * NOTE: This only works fine with uniform scaling. */
+		float scale = 1.0 / length(mat3(invmodel_mat) * wbinor);
+
+		wpos += wbinor * thick_time * scale;
 	}
 }