Volumes: support selection and outlines in viewport

Previously, one could only select a volume object in the outliner
or by clicking on the object origin. This patch allows you to click
on the actual volume.

Furthermore, the generated (invisible) mesh that is used for
selection is also used to draw an outline for the volume object now.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D9022

4 files changed, 55 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_cache.c b/source/blender/draw/intern/draw_cache.c
index 0fbc9e2ed82..52e7e91a995 100644
--- a/source/blender/draw/intern/draw_cache.c
+++ b/source/blender/draw/intern/draw_cache.c
@@ -3279,6 +3279,12 @@ GPUBatch *DRW_cache_volume_face_wireframe_get(Object *ob)
   return DRW_volume_batch_cache_get_wireframes_face(ob->data);
 }
 
+GPUBatch *DRW_cache_volume_selection_surface_get(Object *ob)
+{
+  BLI_assert(ob->type == OB_VOLUME);
+  return DRW_volume_batch_cache_get_selection_surface(ob->data);
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/draw/intern/draw_cache.h b/source/blender/draw/intern/draw_cache.h
index 7164a477d8a..5da9f4b7964 100644
--- a/source/blender/draw/intern/draw_cache.h
+++ b/source/blender/draw/intern/draw_cache.h
@@ -236,6 +236,7 @@ typedef struct DRWVolumeGrid {
 
 DRWVolumeGrid *DRW_volume_batch_cache_get_grid(struct Volume *volume, struct VolumeGrid *grid);
 struct GPUBatch *DRW_cache_volume_face_wireframe_get(struct Object *ob);
+struct GPUBatch *DRW_cache_volume_selection_surface_get(struct Object *ob);
 
 /* GPencil */
 struct GPUBatch *DRW_cache_gpencil_strokes_get(struct Object *ob, int cfra);
diff --git a/source/blender/draw/intern/draw_cache_impl.h b/source/blender/draw/intern/draw_cache_impl.h
index 9e7a2e2916c..e5cc18f6e09 100644
--- a/source/blender/draw/intern/draw_cache_impl.h
+++ b/source/blender/draw/intern/draw_cache_impl.h
@@ -152,6 +152,7 @@ struct GPUBatch **DRW_cache_pointcloud_surface_shaded_get(struct Object *ob,
 int DRW_volume_material_count_get(struct Volume *volume);
 
 struct GPUBatch *DRW_volume_batch_cache_get_wireframes_face(struct Volume *volume);
+struct GPUBatch *DRW_volume_batch_cache_get_selection_surface(struct Volume *volume);
 
 /* Mesh */
 void DRW_mesh_batch_cache_create_requested(struct TaskGraph *task_graph,
diff --git a/source/blender/draw/intern/draw_cache_impl_volume.c b/source/blender/draw/intern/draw_cache_impl_volume.c
index e39c4976e38..7b03070e32b 100644
--- a/source/blender/draw/intern/draw_cache_impl_volume.c
+++ b/source/blender/draw/intern/draw_cache_impl_volume.c
@@ -62,6 +62,9 @@ typedef struct VolumeBatchCache {
     GPUBatch *batch;
   } face_wire;
 
+  /* Surface for selection */
+  GPUBatch *selection_surface;
+
   /* settings to determine if cache is invalid */
   bool is_dirty;
 } VolumeBatchCache;
@@ -132,6 +135,7 @@ static void volume_batch_cache_clear(Volume *volume)
 
   GPU_VERTBUF_DISCARD_SAFE(cache->face_wire.pos_nor_in_order);
   GPU_BATCH_DISCARD_SAFE(cache->face_wire.batch);
+  GPU_BATCH_DISCARD_SAFE(cache->selection_surface);
 }
 
 void DRW_volume_batch_cache_free(Volume *volume)
@@ -209,6 +213,49 @@ GPUBatch *DRW_volume_batch_cache_get_wireframes_face(Volume *volume)
   return cache->face_wire.batch;
 }
 
+static void drw_volume_selection_surface_cb(
+    void *userdata, float (*verts)[3], int (*tris)[3], int totvert, int tottris)
+{
+  Volume *volume = userdata;
+  VolumeBatchCache *cache = volume->batch_cache;
+
+  static GPUVertFormat format = {0};
+  static uint pos_id;
+  if (format.attr_len == 0) {
+    pos_id = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
+  }
+
+  /* Create vertex buffer. */
+  GPUVertBuf *vbo_surface = GPU_vertbuf_create_with_format(&format);
+  GPU_vertbuf_data_alloc(vbo_surface, totvert);
+  GPU_vertbuf_attr_fill(vbo_surface, pos_id, verts);
+
+  /* Create index buffer. */
+  GPUIndexBufBuilder elb;
+  GPU_indexbuf_init(&elb, GPU_PRIM_TRIS, tottris, totvert);
+  for (int i = 0; i < tottris; i++) {
+    GPU_indexbuf_add_tri_verts(&elb, UNPACK3(tris[i]));
+  }
+  GPUIndexBuf *ibo_surface = GPU_indexbuf_build(&elb);
+
+  cache->selection_surface = GPU_batch_create_ex(
+      GPU_PRIM_TRIS, vbo_surface, ibo_surface, GPU_BATCH_OWNS_VBO | GPU_BATCH_OWNS_INDEX);
+}
+
+GPUBatch *DRW_volume_batch_cache_get_selection_surface(Volume *volume)
+{
+  VolumeBatchCache *cache = volume_batch_cache_get(volume);
+  if (cache->selection_surface == NULL) {
+    VolumeGrid *volume_grid = BKE_volume_grid_active_get(volume);
+    if (volume_grid == NULL) {
+      return NULL;
+    }
+    BKE_volume_grid_selection_surface(
+        volume, volume_grid, drw_volume_selection_surface_cb, volume);
+  }
+  return cache->selection_surface;
+}
+
 static DRWVolumeGrid *volume_grid_cache_get(Volume *volume,
                                             VolumeGrid *grid,
                                             VolumeBatchCache *cache)