Fix T73518: Normal Overlay

This change will not render the normals for faces that are hidden.
Before we had instance drawing the hidden faces were registered in the
index buffer. During the overlay refactoring the rendering was migrated
to instance rendering. Instance rendering does not use the index buffer
so the data was ignored.

This patch stored the normal visibility in the .w part of the normal or
for face normals it will set the normal to zero. The shader looks at
this and renders the normals fully transparent when detected.

Reviewed By: Clément Foucault

Differential Revision: https://developer.blender.org/D6798

1 files changed, 18 insertions, 6 deletions

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 2a00160836b..8833490e818 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
@@ -4,8 +4,8 @@ uniform sampler2D depthTex;
 uniform float alpha = 1.0;
 
 in vec3 pos;
-in vec3 lnor;
-in vec3 vnor;
+in vec4 lnor;
+in vec4 vnor;
 in vec4 norAndFlag;
 
 flat out vec4 finalColor;
@@ -22,16 +22,28 @@ void main()
 
   vec3 nor;
   /* Select the right normal by cheking if the generic attrib is used.  */
-  if (!all(equal(lnor, vec3(0)))) {
-    nor = lnor;
+  if (!all(equal(lnor.xyz, vec3(0)))) {
+    if (lnor.w < 0.0) {
+      finalColor = vec4(0.0);
+      return;
+    }
+    nor = lnor.xyz;
     finalColor = colorLNormal;
   }
-  else if (!all(equal(vnor, vec3(0)))) {
-    nor = vnor;
+  else if (!all(equal(vnor.xyz, vec3(0)))) {
+    if (vnor.w < 0.0) {
+      finalColor = vec4(0.0);
+      return;
+    }
+    nor = vnor.xyz;
     finalColor = colorVNormal;
   }
   else {
     nor = norAndFlag.xyz;
+    if (all(equal(nor, vec3(0.0)))) {
+      finalColor = vec4(0.0);
+      return;
+    }
     finalColor = colorNormal;
   }