GPU: Replace `GPUMaterialVolumeGrid` by `GPUMaterialAttribute`

This is to make the codegen and shading nodes object type agnostic. This
is essential for flexibility of the engine to use the nodetree as it see
fits.

The essential volume attributes struct properties are moved to the
`GPUMaterialAttribute` which see its final input name set on creation.

The binding process is centralized into `draw_volume.cc` to avoid
duplicating the code between multiple engines. It mimics the hair attributes
process.

Volume object grid transforms and other per object uniforms are packed into
one UBO per object. The grid transform is now based on object which simplify
the matrix preparations.

This also gets rid of the double transforms and use object info orco factors
for volume objects.

Tagging @brecht because he did the initial implementation of Volume Grids.

2 files changed, 16 insertions, 0 deletions

diff --git a/source/blender/draw/intern/shaders/common_attribute_lib.glsl b/source/blender/draw/intern/shaders/common_attribute_lib.glsl
index 99db2929a13..30239a84c0c 100644
--- a/source/blender/draw/intern/shaders/common_attribute_lib.glsl
+++ b/source/blender/draw/intern/shaders/common_attribute_lib.glsl
@@ -19,3 +19,15 @@ vec4 attr_load_vec4(samplerBuffer attr);
 vec3 attr_load_vec3(samplerBuffer attr);
 vec2 attr_load_vec2(samplerBuffer attr);
 float attr_load_float(samplerBuffer attr);
+
+vec3 attr_load_orco(sampler3D orco);
+vec4 attr_load_tangent(sampler3D tangent);
+vec3 attr_load_uv(sampler3D attr);
+vec4 attr_load_color(sampler3D tex);
+vec4 attr_load_vec4(sampler3D tex);
+vec3 attr_load_vec3(sampler3D tex);
+vec2 attr_load_vec2(sampler3D tex);
+float attr_load_float(sampler3D tex);
+
+float attr_load_temperature_post(float attr);
+vec4 attr_load_color_post(vec4 attr);
diff --git a/source/blender/draw/intern/shaders/draw_object_infos_info.hh b/source/blender/draw/intern/shaders/draw_object_infos_info.hh
index 392b016fc3b..c74a043ec97 100644
--- a/source/blender/draw/intern/shaders/draw_object_infos_info.hh
+++ b/source/blender/draw/intern/shaders/draw_object_infos_info.hh
@@ -6,3 +6,7 @@ GPU_SHADER_CREATE_INFO(draw_object_infos)
     .typedef_source("draw_shader_shared.h")
     .define("OBINFO_LIB")
     .uniform_buf(1, "ObjectInfos", "drw_infos[DRW_RESOURCE_CHUNK_LEN]", Frequency::BATCH);
+
+GPU_SHADER_CREATE_INFO(draw_volume_infos)
+    .typedef_source("draw_shader_shared.h")
+    .uniform_buf(2, "VolumeInfos", "drw_volume", Frequency::BATCH);