Viewport normal drawing with constant length

Patch for: T37878

{F10169694}

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D11487

2 files changed, 23 insertions, 2 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_edit_mesh.c b/source/blender/draw/engines/overlay/overlay_edit_mesh.c
index a7ed6c777e8..3a2871249a2 100644
--- a/source/blender/draw/engines/overlay/overlay_edit_mesh.c
+++ b/source/blender/draw/engines/overlay/overlay_edit_mesh.c
@@ -132,6 +132,11 @@ void OVERLAY_edit_mesh_cache_init(OVERLAY_Data *vedata)
     DRW_shgroup_uniform_float_copy(grp, "normalSize", v3d->overlay.normals_length);
     DRW_shgroup_uniform_float_copy(grp, "alpha", backwire_opacity);
     DRW_shgroup_uniform_texture_ref(grp, "depthTex", depth_tex);
+    DRW_shgroup_uniform_bool_copy(grp,
+                                  "isConstantScreenSizeNormals",
+                                  (flag & V3D_OVERLAY_EDIT_CONSTANT_SCREEN_SIZE_NORMALS) != 0);
+    DRW_shgroup_uniform_float_copy(
+        grp, "normalScreenSize", v3d->overlay.normals_constant_screen_size);
   }
   {
     /* Mesh Analysis Pass */
diff --git a/source/blender/draw/engines/overlay/shaders/edit_mesh_normal_vert.glsl b/source/blender/draw/engines/overlay/shaders/edit_mesh_normal_vert.glsl
index 007495f84e0..f649a5cb3ed 100644
--- a/source/blender/draw/engines/overlay/shaders/edit_mesh_normal_vert.glsl
+++ b/source/blender/draw/engines/overlay/shaders/edit_mesh_normal_vert.glsl
@@ -1,5 +1,7 @@
 
 uniform float normalSize;
+uniform float normalScreenSize;
+uniform bool isConstantScreenSizeNormals;
 uniform sampler2D depthTex;
 uniform float alpha = 1.0;
 
@@ -49,11 +51,25 @@ void main()
   }
 
   vec3 n = normalize(normal_object_to_world(nor));
-
   vec3 world_pos = point_object_to_world(pos);
 
   if (gl_VertexID == 0) {
-    world_pos += n * normalSize;
+    if (isConstantScreenSizeNormals) {
+      bool is_persp = (ProjectionMatrix[3][3] == 0.0);
+      if (is_persp)
+      {
+        float dist_fac = length(cameraPos - world_pos);
+        float cos_fac = dot(cameraForward, cameraVec(world_pos));
+        world_pos += n * normalScreenSize * dist_fac * cos_fac * pixelFac * sizePixel;
+      }
+      else {
+        float frustrum_fac = mul_project_m4_v3_zfac(n) * sizePixel;
+        world_pos += n * normalScreenSize * frustrum_fac;
+      }
+    }
+    else {
+      world_pos += n * normalSize;
+    }
   }
 
   gl_Position = point_world_to_ndc(world_pos);