Fix T99019 EEVEE: Regression: Specular BSDF does not apply occlusion

Since the occlusion input is going to be removed in EEVEE-Next, I just
added a temporary workaround. The occlusion is passed as SSS radius
as the Specular BSDF does not use it.

The final result matches 3.1 release

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/closure_eval_surface_lib.glsl b/source/blender/draw/engines/eevee/shaders/closure_eval_surface_lib.glsl
index 0f5290a7c07..ffca97b6b8f 100644
--- a/source/blender/draw/engines/eevee/shaders/closure_eval_surface_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/closure_eval_surface_lib.glsl
@@ -181,6 +181,8 @@ Closure closure_eval(ClosureDiffuse diffuse, ClosureReflection reflection)
   /* Glue with the old system. */
   CLOSURE_VARS_DECLARE_2(Diffuse, Glossy);
 
+  /* WORKAROUND: This is to avoid regression in 3.2 and avoid messing with EEVEE-Next. */
+  in_common.occlusion = (diffuse.sss_radius.g == -1.0) ? diffuse.sss_radius.r : 1.0;
   in_Diffuse_0.N = diffuse.N;
   in_Diffuse_0.albedo = diffuse.color;
   in_Glossy_1.N = reflection.N;
@@ -207,6 +209,8 @@ Closure closure_eval(ClosureDiffuse diffuse,
   /* Glue with the old system. */
   CLOSURE_VARS_DECLARE_3(Diffuse, Glossy, Glossy);
 
+  /* WORKAROUND: This is to avoid regression in 3.2 and avoid messing with EEVEE-Next. */
+  in_common.occlusion = (diffuse.sss_radius.g == -1.0) ? diffuse.sss_radius.r : 1.0;
   in_Diffuse_0.N = diffuse.N;
   in_Diffuse_0.albedo = diffuse.color;
   in_Glossy_1.N = reflection.N;