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_vert.glsl b/source/blender/draw/engines/eevee/shaders/volumetric_vert.glsl
new file mode 100644
index 00000000000..a99acd41fbd
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/volumetric_vert.glsl
@@ -0,0 +1,27 @@
+
+out vec4 vPos;
+
+void main()
+{
+	/* Generate Triangle : less memory fetches from a VBO */
+	int v_id = gl_VertexID % 3; /* Vertex Id */
+	int t_id = gl_VertexID / 3; /* Triangle Id */
+
+	/* Crappy diagram
+	 * ex 1
+	 *    | \
+	 *    |   \
+	 *  1 |     \
+	 *    |       \
+	 *    |         \
+	 *  0 |           \
+	 *    |             \
+	 *    |               \
+	 * -1 0 --------------- 2
+	 *   -1     0     1     ex
+	 **/
+	vPos.x = float(v_id / 2) * 4.0 - 1.0; /* int divisor round down */
+	vPos.y = float(v_id % 2) * 4.0 - 1.0;
+	vPos.z = float(t_id);
+	vPos.w = 1.0;
+}