Fix T60005: Eevee: Volume material doen't write alpha

2 files changed, 6 insertions, 2 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl b/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
index ade19f4c7a8..5bd5aca576e 100644
--- a/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
@@ -834,7 +834,8 @@ void main()
 #    if defined(USE_ALPHA_BLEND_VOLUMETRICS)
 	/* XXX fragile, better use real viewport resolution */
 	vec2 uvs = gl_FragCoord.xy / vec2(2 * textureSize(maxzBuffer, 0).xy);
-	fragColor = volumetric_resolve(vec4(cl.radiance, cl.opacity), uvs, gl_FragCoord.z);
+	fragColor.rgb = volumetric_resolve(vec4(cl.radiance, cl.opacity), uvs, gl_FragCoord.z).rgb;
+	fragColor.a = cl.opacity;
 #    else
 	fragColor = vec4(cl.radiance, cl.opacity);
 #    endif
diff --git a/source/blender/draw/engines/eevee/shaders/volumetric_lib.glsl b/source/blender/draw/engines/eevee/shaders/volumetric_lib.glsl
index ae36252153f..c5c9ad543db 100644
--- a/source/blender/draw/engines/eevee/shaders/volumetric_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/volumetric_lib.glsl
@@ -151,5 +151,8 @@ vec4 volumetric_resolve(vec4 scene_color, vec2 frag_uvs, float frag_depth)
 	vec3 scattering = texture(inScattering, volume_cos).rgb;
 	vec3 transmittance = texture(inTransmittance, volume_cos).rgb;
 
-	return vec4(scene_color.rgb * transmittance + scattering, scene_color.a);
+	/* Approximate volume alpha by using a monochromatic transmitance
+	 * and adding it to the scene alpha. */
+	float final_alpha = mix(1.0, scene_color.a, dot(transmittance, vec3(1.0 / 3.0)));
+	return vec4(scene_color.rgb * transmittance + scattering, final_alpha);
 }