Eevee: Add support for alpha background in viewport

Viewport now displays alpha checkerboard pattern like Cycles does when
film alpha is set to "Transparent".

Some small workarounds were necessary for Depth of Field and correct TAA
support.

1 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/effect_temporal_aa.glsl b/source/blender/draw/engines/eevee/shaders/effect_temporal_aa.glsl
index 518eff29c62..ac6751fb5fb 100644
--- a/source/blender/draw/engines/eevee/shaders/effect_temporal_aa.glsl
+++ b/source/blender/draw/engines/eevee/shaders/effect_temporal_aa.glsl
@@ -39,7 +39,6 @@ vec3 clip_to_aabb(vec3 color, vec3 minimum, vec3 maximum, vec3 average)
 void main()
 {
   ivec2 texel = ivec2(gl_FragCoord.xy);
-  float depth = texelFetch(depthBuffer, texel, 0).r;
   vec2 motion = texelFetch(velocityBuffer, texel, 0).rg;
 
   /* Decode from unsigned normalized 16bit texture. */
@@ -96,6 +95,9 @@ void main()
   color_history = (out_of_view) ? color : color_history;
 
   FragColor = safe_color(color_history);
+  /* There is some ghost issue if we use the alpha
+   * in the viewport. Overwritting alpha fixes it. */
+  FragColor.a = color.a;
 }
 
 #else