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, 25 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/volumetric_geom.glsl b/source/blender/draw/engines/eevee/shaders/volumetric_geom.glsl
new file mode 100644
index 00000000000..f944184058d
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/volumetric_geom.glsl
@@ -0,0 +1,25 @@
+
+layout(triangles) in;
+layout(triangle_strip, max_vertices=3) out;
+
+in vec4 vPos[];
+
+flat out int slice;
+
+/* This is just a pass-through geometry shader that send the geometry
+ * to the layer corresponding to it's depth. */
+
+void main() {
+	gl_Layer = slice = int(vPos[0].z);
+
+	gl_Position = vPos[0].xyww;
+	EmitVertex();
+
+	gl_Position = vPos[1].xyww;
+	EmitVertex();
+
+	gl_Position = vPos[2].xyww;
+	EmitVertex();
+
+	EndPrimitive();
+}
\ No newline at end of file