From 7df0e8b9492cf74fa73ca908637af9b8327d3afc Mon Sep 17 00:00:00 2001
From: Michael Parkin-White <mparkinwhite@apple.com>
Date: Mon, 13 Mar 2023 14:17:56 +0000
Subject: [PATCH] Fix #103605: Metal barycentric coordinate compilation
 failure.

Fix support for Wireframe and parametric nodes by resolving
compilation failures surrounding barycentric coordinates.
A final missing part of the Metal implementation for barycentric
coordinates was missing.

Feedback also addressed to move barycentric calculation out
of code-gen and into surface_lib.

This also resolves #103606.

Authored by Apple: Michael Parkin-White

Ref #96261
---
 .../engines/eevee/shaders/surface_lib.glsl    | 12 +++++++
 .../blender/gpu/metal/mtl_shader_generator.mm | 31 +++----------------
 2 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/source/blender/draw/engines/eevee/shaders/surface_lib.glsl b/source/blender/draw/engines/eevee/shaders/surface_lib.glsl
index 5ee020358b5..6bd9d222420 100644
--- a/source/blender/draw/engines/eevee/shaders/surface_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/surface_lib.glsl
@@ -101,6 +101,7 @@ SSR_INTERFACE
 #  if defined(USE_BARYCENTRICS) && !defined(HAIR_SHADER)
 vec3 barycentric_distances_get()
 {
+#    if defined(GPU_OPENGL)
   /* NOTE: No need to undo perspective divide since it is not applied yet. */
   vec3 pos0 = (ProjectionMatrixInverse * gpu_position_at_vertex(0)).xyz;
   vec3 pos1 = (ProjectionMatrixInverse * gpu_position_at_vertex(1)).xyz;
@@ -119,6 +120,17 @@ vec3 barycentric_distances_get()
   d = dot(d10, edge21);
   dists.z = sqrt(dot(edge21, edge21) - d * d);
   return dists.xyz;
+#    elif defined(GPU_METAL)
+  /* Calculate Barycentric distances from available parameters in Metal. */
+  float3 wp_delta = (length(dfdx(worldPosition.xyz)) + length(dfdy(worldPosition.xyz)));
+  float3 bc_delta = (length(dfdx(gpu_BaryCoord)) + length(dfdy(gpu_BaryCoord)));
+  float3 rate_of_change = wp_delta / bc_delta;
+  vec3 dists;
+  dists.x = length(rate_of_change * (1.0 - gpu_BaryCoord.x));
+  dists.y = length(rate_of_change * (1.0 - gpu_BaryCoord.y));
+  dists.z = length(rate_of_change * (1.0 - gpu_BaryCoord.z));
+  return dists.xyz;
+#    endif
 }
 #  endif
 
diff --git a/source/blender/gpu/metal/mtl_shader_generator.mm b/source/blender/gpu/metal/mtl_shader_generator.mm
index 5810ed79f33..7be93ce04ce 100644
--- a/source/blender/gpu/metal/mtl_shader_generator.mm
+++ b/source/blender/gpu/metal/mtl_shader_generator.mm
@@ -1268,6 +1268,11 @@ bool MTLShader::generate_msl_from_glsl(const shader::ShaderCreateInfo *info)
       ss_fragment << "uint gl_PrimitiveID;" << std::endl;
     }
 
+    /* Global barycentrics. */
+    if (msl_iface.uses_barycentrics) {
+      ss_fragment << "vec3 gpu_BaryCoord;\n";
+    }
+
     /* Add Texture members. */
     for (const MSLTextureSampler &tex : msl_iface.texture_samplers) {
       if (bool(tex.stage & ShaderStage::FRAGMENT)) {
@@ -2036,33 +2041,7 @@ std::string MSLGeneratorInterface::generate_msl_fragment_entry_stub()
 
   /* Barycentrics. */
   if (this->uses_barycentrics) {
-
-    /* Main barycentrics. */
     out << shader_stage_inst_name << ".gpu_BaryCoord = mtl_barycentric_coord.xyz;" << std::endl;
-
-    /* barycentricDist represents the world-space distance from the current world-space position
-     * to the opposite edge of the vertex. */
-    out << "float3 worldPos = " << shader_stage_inst_name << ".worldPosition.xyz;" << std::endl;
-    out << "float3 wpChange = (length(dfdx(worldPos))+length(dfdy(worldPos)));" << std::endl;
-    out << "float3 bcChange = "
-           "(length(dfdx(mtl_barycentric_coord))+length(dfdy(mtl_barycentric_coord)));"
-        << std::endl;
-    out << "float3 rateOfChange = wpChange/bcChange;" << std::endl;
-
-    /* Distance to edge using inverse barycentric value, as rather than the length of 0.7
-     * contribution, we'd want the distance to the opposite side. */
-    out << shader_stage_inst_name
-        << ".gpu_BarycentricDist.x = length(rateOfChange * "
-           "(1.0-mtl_barycentric_coord.x));"
-        << std::endl;
-    out << shader_stage_inst_name
-        << ".gpu_BarycentricDist.y = length(rateOfChange * "
-           "(1.0-mtl_barycentric_coord.y));"
-        << std::endl;
-    out << shader_stage_inst_name
-        << ".gpu_BarycentricDist.z = length(rateOfChange * "
-           "(1.0-mtl_barycentric_coord.z));"
-        << std::endl;
   }
 
   /* Populate Uniforms and uniform blocks. */
-- 
2.30.2