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.

1 files changed, 14 insertions, 224 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_volumes.c b/source/blender/draw/engines/eevee/eevee_volumes.c
index 0ac6c6ad97c..b8bef61f8b1 100644
--- a/source/blender/draw/engines/eevee/eevee_volumes.c
+++ b/source/blender/draw/engines/eevee/eevee_volumes.c
@@ -45,30 +45,6 @@ static struct {
   GPUTexture *dummy_transmit;
 } e_data = {NULL}; /* Engine data */
 
-static void eevee_create_textures_volumes(void)
-{
-  const float zero[4] = {0.0f, 0.0f, 0.0f, 0.0f};
-  e_data.dummy_zero = DRW_texture_create_3d(1, 1, 1, GPU_RGBA8, DRW_TEX_WRAP, zero);
-
-  const float one[4] = {1.0f, 1.0f, 1.0f, 1.0f};
-  e_data.dummy_one = DRW_texture_create_3d(1, 1, 1, GPU_RGBA8, DRW_TEX_WRAP, one);
-
-  const float flame = 0.0f;
-  e_data.dummy_flame = DRW_texture_create_3d(1, 1, 1, GPU_R8, DRW_TEX_WRAP, &flame);
-}
-
-static GPUTexture *eevee_volume_default_texture(eGPUVolumeDefaultValue default_value)
-{
-  switch (default_value) {
-    case GPU_VOLUME_DEFAULT_0:
-      return e_data.dummy_zero;
-    case GPU_VOLUME_DEFAULT_1:
-      return e_data.dummy_one;
-  }
-
-  return e_data.dummy_zero;
-}
-
 void EEVEE_volumes_set_jitter(EEVEE_ViewLayerData *sldata, uint current_sample)
 {
   EEVEE_CommonUniformBuffer *common_data = &sldata->common_data;
@@ -224,11 +200,6 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
   Scene *scene = draw_ctx->scene;
   DRWShadingGroup *grp = NULL;
 
-  /* Textures */
-  if (!e_data.dummy_zero) {
-    eevee_create_textures_volumes();
-  }
-
   /* Quick breakdown of the Volumetric rendering:
    *
    * The rendering is separated in 4 stages:
@@ -265,7 +236,7 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
       !LOOK_DEV_STUDIO_LIGHT_ENABLED(draw_ctx->v3d)) {
     struct GPUMaterial *mat = EEVEE_material_get(vedata, scene, NULL, wo, VAR_MAT_VOLUME);
 
-    if (GPU_material_has_volume_output(mat)) {
+    if (mat && GPU_material_has_volume_output(mat)) {
       grp = DRW_shgroup_material_create(mat, psl->volumetric_world_ps);
     }
 
@@ -280,11 +251,7 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
       DRW_shgroup_uniform_block(grp, "renderpass_block", sldata->renderpass_ubo.combined);
 
       /* Fix principle volumetric not working with world materials. */
-      ListBase gpu_grids = GPU_material_volume_grids(mat);
-      LISTBASE_FOREACH (GPUMaterialVolumeGrid *, gpu_grid, &gpu_grids) {
-        DRW_shgroup_uniform_texture(
-            grp, gpu_grid->sampler_name, eevee_volume_default_texture(gpu_grid->default_value));
-      }
+      grp = DRW_shgroup_volume_create_sub(NULL, NULL, grp, mat);
 
       DRW_shgroup_call_procedural_triangles(grp, NULL, common_data->vol_tex_size[2]);
 
@@ -296,186 +263,17 @@ void EEVEE_volumes_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     /* If no world or volume material is present just clear the buffer with this drawcall */
     grp = DRW_shgroup_create(EEVEE_shaders_volumes_clear_sh_get(), psl->volumetric_world_ps);
     DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
+    DRW_shgroup_uniform_block(grp, "grid_block", sldata->grid_ubo);
     DRW_shgroup_uniform_block(grp, "probe_block", sldata->probe_ubo);
+    DRW_shgroup_uniform_block(grp, "planar_block", sldata->planar_ubo);
     DRW_shgroup_uniform_block(grp, "light_block", sldata->light_ubo);
+    DRW_shgroup_uniform_block(grp, "shadow_block", sldata->shadow_ubo);
     DRW_shgroup_uniform_block(grp, "renderpass_block", sldata->renderpass_ubo.combined);
 
     DRW_shgroup_call_procedural_triangles(grp, NULL, common_data->vol_tex_size[2]);
   }
 }
 
-static bool eevee_volume_object_grids_init(Object *ob, ListBase *gpu_grids, DRWShadingGroup *grp)
-{
-  Volume *volume = ob->data;
-  BKE_volume_load(volume, G.main);
-
-  /* Test if we need to use multiple transforms. */
-  DRWVolumeGrid *first_drw_grid = NULL;
-  bool multiple_transforms = true;
-
-  LISTBASE_FOREACH (GPUMaterialVolumeGrid *, gpu_grid, gpu_grids) {
-    const VolumeGrid *volume_grid = BKE_volume_grid_find_for_read(volume, gpu_grid->name);
-    DRWVolumeGrid *drw_grid = (volume_grid) ?
-                                  DRW_volume_batch_cache_get_grid(volume, volume_grid) :
-                                  NULL;
-
-    if (drw_grid) {
-      if (first_drw_grid == NULL) {
-        first_drw_grid = drw_grid;
-      }
-      else if (drw_grid &&
-               !equals_m4m4(drw_grid->object_to_texture, first_drw_grid->object_to_texture)) {
-        multiple_transforms = true;
-        break;
-      }
-    }
-  }
-
-  /* Bail out of no grids to render. */
-  if (first_drw_grid == NULL) {
-    return false;
-  }
-
-  /* Set transform matrix for the volume as a whole. This one is also used for
-   * clipping so must map the entire bounding box to 0..1. */
-  float bounds_to_object[4][4];
-
-  if (multiple_transforms) {
-    /* For multiple grids with different transform, we first transform from object space
-     * to bounds, then for each individual grid from bounds to texture. */
-    const BoundBox *bb = BKE_volume_boundbox_get(ob);
-    float bb_size[3];
-    sub_v3_v3v3(bb_size, bb->vec[6], bb->vec[0]);
-    size_to_mat4(bounds_to_object, bb_size);
-    copy_v3_v3(bounds_to_object[3], bb->vec[0]);
-
-    invert_m4_m4(first_drw_grid->object_to_bounds, bounds_to_object);
-    DRW_shgroup_uniform_mat4(grp, "volumeObjectToTexture", first_drw_grid->object_to_bounds);
-  }
-  else {
-    /* All grid transforms are equal, we can transform to texture space immediately. */
-    DRW_shgroup_uniform_mat4(grp, "volumeObjectToTexture", first_drw_grid->object_to_texture);
-  }
-
-  /* Don't use orco transform here, only matrix. */
-  DRW_shgroup_uniform_vec3_copy(grp, "volumeOrcoLoc", (float[3]){0.5f, 0.5f, 0.5f});
-  DRW_shgroup_uniform_vec3_copy(grp, "volumeOrcoSize", (float[3]){0.5f, 0.5f, 0.5f});
-
-  /* Set density scale. */
-  const float density_scale = BKE_volume_density_scale(volume, ob->obmat);
-  DRW_shgroup_uniform_float_copy(grp, "volumeDensityScale", density_scale);
-
-  /* Bind volume grid textures. */
-  LISTBASE_FOREACH (GPUMaterialVolumeGrid *, gpu_grid, gpu_grids) {
-    const VolumeGrid *volume_grid = BKE_volume_grid_find_for_read(volume, gpu_grid->name);
-    DRWVolumeGrid *drw_grid = (volume_grid) ?
-                                  DRW_volume_batch_cache_get_grid(volume, volume_grid) :
-                                  NULL;
-
-    /* Handle 3 cases here:
-     * - Grid exists and texture was loaded -> use texture.
-     * - Grid exists but has zero size or failed to load -> use zero.
-     * - Grid does not exist -> use default value. */
-    GPUTexture *grid_tex = (drw_grid)    ? drw_grid->texture :
-                           (volume_grid) ? e_data.dummy_zero :
-                                           eevee_volume_default_texture(gpu_grid->default_value);
-
-    DRW_shgroup_uniform_texture(grp, gpu_grid->sampler_name, grid_tex);
-
-    if (drw_grid && multiple_transforms) {
-      /* Specify per-volume transform matrix that is applied after the
-       * transform from object to bounds. */
-      mul_m4_m4m4(drw_grid->bounds_to_texture, drw_grid->object_to_texture, bounds_to_object);
-      DRW_shgroup_uniform_mat4(grp, gpu_grid->transform_name, drw_grid->bounds_to_texture);
-    }
-  }
-
-  return true;
-}
-
-static bool eevee_volume_object_mesh_init(Scene *scene,
-                                          Object *ob,
-                                          ListBase *gpu_grids,
-                                          DRWShadingGroup *grp)
-{
-  static const float white[3] = {1.0f, 1.0f, 1.0f};
-  ModifierData *md = NULL;
-
-  /* Smoke Simulation */
-  if ((md = BKE_modifiers_findby_type(ob, eModifierType_Fluid)) &&
-      (BKE_modifier_is_enabled(scene, md, eModifierMode_Realtime)) &&
-      ((FluidModifierData *)md)->domain != NULL) {
-    FluidModifierData *fmd = (FluidModifierData *)md;
-    FluidDomainSettings *fds = fmd->domain;
-
-    /* Don't try to show liquid domains here. */
-    if (!fds->fluid || !(fds->type == FLUID_DOMAIN_TYPE_GAS)) {
-      return false;
-    }
-
-    /* Don't show smoke before simulation starts, this could be made an option in the future. */
-    /* (sebbas): Always show smoke for manta */
-#if 0
-    const DRWContextState *draw_ctx = DRW_context_state_get();
-    const bool show_smoke = ((int)DEG_get_ctime(draw_ctx->depsgraph) >=
-                             *fds->point_cache[0]->startframe);
-#endif
-
-    if (fds->fluid && (fds->type == FLUID_DOMAIN_TYPE_GAS) /* && show_smoke */) {
-      DRW_smoke_ensure(fmd, fds->flags & FLUID_DOMAIN_USE_NOISE);
-    }
-
-    LISTBASE_FOREACH (GPUMaterialVolumeGrid *, gpu_grid, gpu_grids) {
-      if (STREQ(gpu_grid->name, "density")) {
-        DRW_shgroup_uniform_texture_ref(
-            grp, gpu_grid->sampler_name, fds->tex_density ? &fds->tex_density : &e_data.dummy_one);
-      }
-      else if (STREQ(gpu_grid->name, "color")) {
-        DRW_shgroup_uniform_texture_ref(
-            grp, gpu_grid->sampler_name, fds->tex_color ? &fds->tex_color : &e_data.dummy_one);
-      }
-      else if (STR_ELEM(gpu_grid->name, "flame", "temperature")) {
-        DRW_shgroup_uniform_texture_ref(
-            grp, gpu_grid->sampler_name, fds->tex_flame ? &fds->tex_flame : &e_data.dummy_flame);
-      }
-      else {
-        DRW_shgroup_uniform_texture(
-            grp, gpu_grid->sampler_name, eevee_volume_default_texture(gpu_grid->default_value));
-      }
-    }
-
-    /* Constant Volume color. */
-    bool use_constant_color = ((fds->active_fields & FLUID_DOMAIN_ACTIVE_COLORS) == 0 &&
-                               (fds->active_fields & FLUID_DOMAIN_ACTIVE_COLOR_SET) != 0);
-
-    DRW_shgroup_uniform_vec3(
-        grp, "volumeColor", (use_constant_color) ? fds->active_color : white, 1);
-
-    /* Output is such that 0..1 maps to 0..1000K */
-    DRW_shgroup_uniform_vec2(grp, "volumeTemperature", &fds->flame_ignition, 1);
-  }
-  else {
-    LISTBASE_FOREACH (GPUMaterialVolumeGrid *, gpu_grid, gpu_grids) {
-      DRW_shgroup_uniform_texture(
-          grp, gpu_grid->sampler_name, eevee_volume_default_texture(gpu_grid->default_value));
-    }
-  }
-
-  /* Transform for mesh volumes. */
-  static const float unit_mat[4][4] = {{1.0f, 0.0f, 0.0f, 0.0f},
-                                       {0.0f, 1.0f, 0.0f, 0.0f},
-                                       {0.0f, 0.0f, 1.0f, 0.0f},
-                                       {0.0f, 0.0f, 0.0f, 1.0f}};
-  float *texco_loc, *texco_size;
-  BKE_mesh_texspace_get_reference((struct Mesh *)ob->data, NULL, &texco_loc, &texco_size);
-
-  DRW_shgroup_uniform_mat4(grp, "volumeObjectToTexture", unit_mat);
-  DRW_shgroup_uniform_vec3(grp, "volumeOrcoLoc", texco_loc, 1);
-  DRW_shgroup_uniform_vec3(grp, "volumeOrcoSize", texco_size, 1);
-
-  return true;
-}
-
 void EEVEE_volumes_cache_object_add(EEVEE_ViewLayerData *sldata,
                                     EEVEE_Data *vedata,
                                     Scene *scene,
@@ -502,15 +300,22 @@ void EEVEE_volumes_cache_object_add(EEVEE_ViewLayerData *sldata,
 
   int mat_options = VAR_MAT_VOLUME | VAR_MAT_MESH;
   struct GPUMaterial *mat = EEVEE_material_get(vedata, scene, ma, NULL, mat_options);
-  eGPUMaterialStatus status = GPU_material_status(mat);
 
   /* If shader failed to compile or is currently compiling. */
-  if (status != GPU_MAT_SUCCESS) {
+  if (mat == NULL) {
     return;
   }
 
+  /* TODO(fclem): Reuse main shading group to avoid shading binding cost just like for surface
+   * shaders. */
   DRWShadingGroup *grp = DRW_shgroup_material_create(mat, vedata->psl->volumetric_objects_ps);
 
+  grp = DRW_shgroup_volume_create_sub(scene, ob, grp, mat);
+
+  if (grp == NULL) {
+    return;
+  }
+
   /* TODO(fclem): remove those "unnecessary" UBOs */
   DRW_shgroup_uniform_block(grp, "planar_block", sldata->planar_ubo);
   DRW_shgroup_uniform_block(grp, "probe_block", sldata->probe_ubo);
@@ -518,22 +323,7 @@ void EEVEE_volumes_cache_object_add(EEVEE_ViewLayerData *sldata,
   DRW_shgroup_uniform_block(grp, "light_block", sldata->light_ubo);
   DRW_shgroup_uniform_block(grp, "grid_block", sldata->grid_ubo);
   DRW_shgroup_uniform_block(grp, "renderpass_block", sldata->renderpass_ubo.combined);
-
   DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
-
-  ListBase gpu_grids = GPU_material_volume_grids(mat);
-
-  if (ob->type == OB_VOLUME) {
-    if (!eevee_volume_object_grids_init(ob, &gpu_grids, grp)) {
-      return;
-    }
-  }
-  else {
-    if (!eevee_volume_object_mesh_init(scene, ob, &gpu_grids, grp)) {
-      return;
-    }
-  }
-
   /* TODO: Reduce to number of slices intersecting. */
   /* TODO: Preemptive culling. */
   DRW_shgroup_call_procedural_triangles(grp, ob, sldata->common_data.vol_tex_size[2]);