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

1 files changed, 47 insertions, 0 deletions

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)