UI/Assets: Support generating object preview images

Object previews are really helpful for visual data-block selection, like asset
browsing. Having them be generative should also be quite handy and should work
well enough in many, if not most cases.

What this does is simple:
* Place the object (actually a deep copy of it, for thread safety) in a virtual
  .blend into an empty scene/view-layer.
* Add a camera, point it towards the front of the object, assuming that means
  pointing towards its +Y axis.
* Use "Camera Fit Frame to Selected" logic to put the object into frame.
* Create a threaded off-screen render.

Of course, such an automatic preview will not work in all situations. E.g. it
currently does a bad job capturing a single plane. We could add options for
more advanced automatic previews, but probably custom previews is more
important, which I committed already (812ea9184221).

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Reviewed as part of https://developer.blender.org/D9719.
Reviewed by: Bastien Montagne, Brecht Van Lommel

1 files changed, 3 insertions, 25 deletions

diff --git a/source/blender/editors/space_view3d/view3d_view.c b/source/blender/editors/space_view3d/view3d_view.c
index a24f59019f0..9d947384bf0 100644
--- a/source/blender/editors/space_view3d/view3d_view.c
+++ b/source/blender/editors/space_view3d/view3d_view.c
@@ -535,40 +535,18 @@ void VIEW3D_OT_camera_to_view(wmOperatorType *ot)
  * meant to take into account vertex/bone selection for eg. */
 static int view3d_camera_to_view_selected_exec(bContext *C, wmOperator *op)
 {
+  Main *bmain = CTX_data_main(C);
   Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
   Scene *scene = CTX_data_scene(C);
   View3D *v3d = CTX_wm_view3d(C); /* can be NULL */
   Object *camera_ob = v3d ? v3d->camera : scene->camera;
-  Object *camera_ob_eval = DEG_get_evaluated_object(depsgraph, camera_ob);
-
-  float r_co[3]; /* the new location to apply */
-  float r_scale; /* only for ortho cameras */
 
-  if (camera_ob_eval == NULL) {
+  if (camera_ob == NULL) {
     BKE_report(op->reports, RPT_ERROR, "No active camera");
     return OPERATOR_CANCELLED;
   }
 
-  /* this function does all the important stuff */
-  if (BKE_camera_view_frame_fit_to_scene(depsgraph, scene, camera_ob_eval, r_co, &r_scale)) {
-    ObjectTfmProtectedChannels obtfm;
-    float obmat_new[4][4];
-
-    if ((camera_ob_eval->type == OB_CAMERA) &&
-        (((Camera *)camera_ob_eval->data)->type == CAM_ORTHO)) {
-      ((Camera *)camera_ob->data)->ortho_scale = r_scale;
-    }
-
-    copy_m4_m4(obmat_new, camera_ob_eval->obmat);
-    copy_v3_v3(obmat_new[3], r_co);
-
-    /* only touch location */
-    BKE_object_tfm_protected_backup(camera_ob, &obtfm);
-    BKE_object_apply_mat4(camera_ob, obmat_new, true, true);
-    BKE_object_tfm_protected_restore(camera_ob, &obtfm, OB_LOCK_SCALE | OB_LOCK_ROT4D);
-
-    /* notifiers */
-    DEG_id_tag_update(&camera_ob->id, ID_RECALC_TRANSFORM);
+  if (ED_view3d_camera_to_view_selected(bmain, depsgraph, scene, camera_ob)) {
     WM_event_add_notifier(C, NC_OBJECT | ND_TRANSFORM, camera_ob);
     return OPERATOR_FINISHED;
   }