Eevee: Overhaul the volumetric system.

The system now uses several 3D textures in order to decouple every steps of the volumetric rendering.

See https://www.ea.com/frostbite/news/physically-based-unified-volumetric-rendering-in-frostbite for more details.

On the technical side, instead of using a compute shader to populate the 3D textures we use layered rendering with a geometry shader to render 1 fullscreen triangle per 3D texture slice.

1 files changed, 27 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/volumetric_resolve_frag.glsl b/source/blender/draw/engines/eevee/shaders/volumetric_resolve_frag.glsl
new file mode 100644
index 00000000000..3e678bbc83f
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/volumetric_resolve_frag.glsl
@@ -0,0 +1,27 @@
+
+/* Based on Frosbite Unified Volumetric.
+ * https://www.ea.com/frostbite/news/physically-based-unified-volumetric-rendering-in-frostbite */
+
+/* Step 4 : Apply final integration on top of the scene color.
+ * Note that we do the blending ourself instead of relying
+ * on hardware blending which would require 2 pass. */
+
+uniform sampler3D inScattering;
+uniform sampler3D inTransmittance;
+
+uniform sampler2D inSceneColor;
+uniform sampler2D inSceneDepth;
+
+out vec4 FragColor;
+
+void main()
+{
+	vec2 uvs = gl_FragCoord.xy / vec2(textureSize(inSceneDepth, 0));
+	vec3 volume_cos = ndc_to_volume(vec3(uvs, texture(inSceneDepth, uvs).r));
+
+	vec3 scene_color = texture(inSceneColor, uvs).rgb;
+	vec3 scattering = texture(inScattering, volume_cos).rgb;
+	vec3 transmittance = texture(inTransmittance, volume_cos).rgb;
+
+	FragColor = vec4(scene_color * transmittance + scattering, 1.0);
+}