Volumes: support lower resolution in viewport

The adds a new option to simplify volumes in the viewport.
The setting can be found in the Simplify panel in the render properties.

Volume objects use OpenVDB grids, which are sparse. For rendering,
we have to convert sparse grids to dense grids (for now). Those require
significantly more memory. Therefore, it's often a good idea to reduce
the resolution of volumes in the viewport.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D9040

Ref T73201.

1 files changed, 23 insertions, 22 deletions

diff --git a/source/blender/draw/intern/draw_cache_impl_volume.c b/source/blender/draw/intern/draw_cache_impl_volume.c
index 7b03070e32b..10bacadb199 100644
--- a/source/blender/draw/intern/draw_cache_impl_volume.c
+++ b/source/blender/draw/intern/draw_cache_impl_volume.c
@@ -42,6 +42,8 @@
 #include "GPU_batch.h"
 #include "GPU_texture.h"
 
+#include "DEG_depsgraph_query.h"
+
 #include "DRW_render.h"
 
 #include "draw_cache.h"      /* own include */
@@ -260,6 +262,8 @@ static DRWVolumeGrid *volume_grid_cache_get(Volume *volume,
                                             VolumeGrid *grid,
                                             VolumeBatchCache *cache)
 {
+  const DRWContextState *draw_ctx = DRW_context_state_get();
+
   const char *name = BKE_volume_grid_name(grid);
 
   /* Return cached grid. */
@@ -289,35 +293,32 @@ static DRWVolumeGrid *volume_grid_cache_get(Volume *volume,
   const bool was_loaded = BKE_volume_grid_is_loaded(grid);
   BKE_volume_grid_load(volume, grid);
 
-  /* Compute dense voxel grid size. */
-  int64_t dense_min[3], dense_max[3], resolution[3] = {0};
-  if (BKE_volume_grid_dense_bounds(volume, grid, dense_min, dense_max)) {
-    resolution[0] = dense_max[0] - dense_min[0];
-    resolution[1] = dense_max[1] - dense_min[1];
-    resolution[2] = dense_max[2] - dense_min[2];
+  float resolution_factor = 1.0f;
+  if (DEG_get_mode(draw_ctx->depsgraph) != DAG_EVAL_RENDER) {
+    if (draw_ctx->scene->r.mode & R_SIMPLIFY) {
+      resolution_factor = draw_ctx->scene->r.simplify_volumes;
+    }
+  }
+  if (resolution_factor == 0.0f) {
+    return cache_grid;
   }
-  size_t num_voxels = resolution[0] * resolution[1] * resolution[2];
-  size_t elem_size = sizeof(float) * channels;
 
-  /* Allocate and load voxels. */
-  float *voxels = (num_voxels > 0) ? MEM_malloc_arrayN(num_voxels, elem_size, __func__) : NULL;
-  if (voxels != NULL) {
-    BKE_volume_grid_dense_voxels(volume, grid, dense_min, dense_max, voxels);
+  DenseFloatVolumeGrid dense_grid;
+  if (BKE_volume_grid_dense_floats(volume, grid, resolution_factor, &dense_grid)) {
+    copy_m4_m4(cache_grid->texture_to_object, dense_grid.texture_to_object);
+    invert_m4_m4(cache_grid->object_to_texture, dense_grid.texture_to_object);
 
     /* Create GPU texture. */
     eGPUTextureFormat format = (channels == 3) ? GPU_RGB16F : GPU_R16F;
-    cache_grid->texture = GPU_texture_create_3d(
-        "volume_grid", UNPACK3(resolution), 1, format, GPU_DATA_FLOAT, voxels);
-
+    cache_grid->texture = GPU_texture_create_3d("volume_grid",
+                                                UNPACK3(dense_grid.resolution),
+                                                1,
+                                                format,
+                                                GPU_DATA_FLOAT,
+                                                dense_grid.voxels);
     GPU_texture_swizzle_set(cache_grid->texture, (channels == 3) ? "rgb1" : "rrr1");
     GPU_texture_wrap_mode(cache_grid->texture, false, false);
-
-    MEM_freeN(voxels);
-
-    /* Compute transform matrices. */
-    BKE_volume_grid_dense_transform_matrix(
-        grid, dense_min, dense_max, cache_grid->texture_to_object);
-    invert_m4_m4(cache_grid->object_to_texture, cache_grid->texture_to_object);
+    BKE_volume_dense_float_grid_clear(&dense_grid);
   }
 
   /* Free grid from memory if it wasn't previously loaded. */