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.

2 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/draw/intern/DRW_render.h b/source/blender/draw/intern/DRW_render.h
index 92213a0bee0..599656ae163 100644
--- a/source/blender/draw/intern/DRW_render.h
+++ b/source/blender/draw/intern/DRW_render.h
@@ -302,6 +302,7 @@ DRWShadingGroup *DRW_shgroup_create(struct GPUShader *shader, DRWPass *pass);
 DRWShadingGroup *DRW_shgroup_material_create(struct GPUMaterial *material, DRWPass *pass);
 DRWShadingGroup *DRW_shgroup_material_instance_create(
         struct GPUMaterial *material, DRWPass *pass, struct Gwn_Batch *geom, struct Object *ob);
+DRWShadingGroup *DRW_shgroup_material_empty_tri_batch_create(struct GPUMaterial *material, DRWPass *pass, int size);
 DRWShadingGroup *DRW_shgroup_instance_create(struct GPUShader *shader, DRWPass *pass, struct Gwn_Batch *geom);
 DRWShadingGroup *DRW_shgroup_point_batch_create(struct GPUShader *shader, DRWPass *pass);
 DRWShadingGroup *DRW_shgroup_line_batch_create(struct GPUShader *shader, DRWPass *pass);
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index 0329b3c3121..63910321f39 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -878,6 +878,20 @@ DRWShadingGroup *DRW_shgroup_material_instance_create(
 	return shgroup;
 }
 
+DRWShadingGroup *DRW_shgroup_material_empty_tri_batch_create(
+        struct GPUMaterial *material, DRWPass *pass, int size)
+{
+	DRWShadingGroup *shgroup = DRW_shgroup_material_create(material, pass);
+
+	if (shgroup) {
+		shgroup->type = DRW_SHG_TRIANGLE_BATCH;
+		shgroup->interface->instance_count = size * 3;
+		DRW_interface_attrib(shgroup, "dummy", DRW_ATTRIB_FLOAT, 1, true);
+	}
+
+	return shgroup;
+}
+
 DRWShadingGroup *DRW_shgroup_instance_create(struct GPUShader *shader, DRWPass *pass, Gwn_Batch *geom)
 {
 	DRWShadingGroup *shgroup = DRW_shgroup_create(shader, pass);