EEVEE: Deffered: Change normal packing for better negative normals

The spheremap encoding has a singularity issue for inverted normals
which are used by the translucent BSDF. This fixes the issue.

3 files changed, 30 insertions, 15 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/eevee_gbuffer_lib.glsl b/source/blender/draw/engines/eevee/shaders/eevee_gbuffer_lib.glsl
index caec0fb1673..15a1349c417 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_gbuffer_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_gbuffer_lib.glsl
@@ -25,12 +25,24 @@ float gbuffer_decode_unit_float_from_uint(uint packed_scalar, const uint bit_siz
 /* Expects input to be normalized. */
 vec2 gbuffer_encode_normal(vec3 normal)
 {
-  return normal_encode(normal_world_to_view(normal));
+  vec3 vN = normal_world_to_view(normal);
+  bool neg = vN.z < 0.0;
+  if (neg) {
+    vN.z = -vN.z;
+  }
+  vec2 packed_normal = normal_encode(vN);
+  // return packed_normal;
+  return (neg) ? -packed_normal : packed_normal;
 }
 
 vec3 gbuffer_decode_normal(vec2 packed_normal)
 {
-  return normal_view_to_world(normal_decode(packed_normal));
+  bool neg = packed_normal.y < 0.0;
+  vec3 vN = normal_decode(abs(packed_normal));
+  if (neg) {
+    vN.z = -vN.z;
+  }
+  return normal_view_to_world(vN);
 }
 
 /* Note: does not handle negative colors. */
@@ -89,16 +101,18 @@ void gbuffer_load_global_data(vec4 transmit_normal_in, out float thickness)
 ClosureDiffuse gbuffer_load_diffuse_data(vec4 color_in, vec4 normal_in, vec4 data_in)
 {
   ClosureDiffuse data_out;
-  if (normal_in.x > 0.0) {
-    data_out.color = color_in.rgb;
-    data_out.N = gbuffer_decode_normal(normal_in.xy);
-  }
-  else {
+  if (normal_in.z == -1.0) {
+    /* Transmission data is Refraction data. */
     data_out.color = vec3(0.0);
     data_out.N = vec3(1.0);
+    data_out.sss_id = 0u;
+  }
+  else {
+    data_out.color = color_in.rgb;
+    data_out.N = gbuffer_decode_normal(normal_in.xy);
+    data_out.sss_id = uint(normal_in.z * 1024.0);
   }
   data_out.sss_radius = data_in.rgb;
-  data_out.sss_id = uint(normal_in.z * 1024.0);
   return data_out;
 }
 
@@ -137,9 +151,9 @@ ClosureReflection gbuffer_load_reflection_data(sampler2D reflect_color_tx,
 ClosureRefraction gbuffer_load_refraction_data(vec4 color_in, vec4 normal_in, vec4 data_in)
 {
   ClosureRefraction data_out;
-  if (normal_in.x < 0.0) {
+  if (normal_in.z == -1.0) {
     data_out.color = color_in.rgb;
-    data_out.N = gbuffer_decode_normal(-normal_in.xy);
+    data_out.N = gbuffer_decode_normal(normal_in.xy);
     data_out.ior = data_in.x;
     data_out.roughness = data_in.y;
   }
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
index 9e0a07d9c94..de4c8cb59a6 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
@@ -74,14 +74,15 @@ void main(void)
   vec4 tra_nor_in = texture(transmit_normal_tx, center_uv);
   vec4 tra_dat_in = texture(transmit_data_tx, center_uv);
 
-  if (tra_nor_in.x < 0.0) {
-    /* Refraction transmission case. */
+  ClosureDiffuse diffuse = gbuffer_load_diffuse_data(tra_col_in, tra_nor_in, tra_dat_in);
+
+  if (diffuse.sss_id <= 0u) {
+    /* Normal diffuse is already in combined pass. */
+    /* Refraction also go into this case. */
     out_combined = vec4(0.0);
     return;
   }
 
-  ClosureDiffuse diffuse = gbuffer_load_diffuse_data(tra_col_in, tra_nor_in, tra_dat_in);
-
   float max_radius = max_v3(diffuse.sss_radius);
 
   float homcoord = ProjectionMatrix[2][3] * vP.z + ProjectionMatrix[3][3];
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_surface_deferred_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_surface_deferred_frag.glsl
index 7578794c206..51e00ef43d3 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_surface_deferred_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_surface_deferred_frag.glsl
@@ -75,7 +75,7 @@ void main(void)
 
   if (g_data.transmit_rand == 0.0) {
     out_transmit_color = g_refraction_data.color;
-    out_transmit_normal.xy = -gbuffer_encode_normal(g_refraction_data.N);
+    out_transmit_normal.xy = gbuffer_encode_normal(g_refraction_data.N);
     out_transmit_normal.z = -1.0;
     out_transmit_normal.w = thickness;
     out_transmit_data.x = g_refraction_data.ior;