Fix MultiMesh visible_instance_count being ignored after the first frame

Co-authored-by: Clay John <[email protected]>

drivers/gles3/storage/mesh_storage.cpp

@@ -1835,8 +1835,12 @@ void MeshStorage::multimesh_set_visible_instances(RID p_multimesh, int p_visible
 	}
 
 	if (multimesh->data_cache.size()) {
-		//there is a data cache..
+		// There is a data cache, but we may need to update some sections.
 		_multimesh_mark_all_dirty(multimesh, false, true);
+		int start = multimesh->visible_instances >= 0 ? multimesh->visible_instances : multimesh->instances;
+		for (int i = start; i < p_visible; i++) {
+			_multimesh_mark_dirty(multimesh, i, true);
+		}
 	}
 
 	multimesh->visible_instances = p_visible;
@@ -1868,7 +1872,7 @@ void MeshStorage::_update_dirty_multimeshes() {
 				if (multimesh->data_cache_used_dirty_regions > 32 || multimesh->data_cache_used_dirty_regions > visible_region_count / 2) {
 					// If there too many dirty regions, or represent the majority of regions, just copy all, else transfer cost piles up too much
 					glBindBuffer(GL_ARRAY_BUFFER, multimesh->buffer);
-					glBufferData(GL_ARRAY_BUFFER, MIN(visible_region_count * region_size, multimesh->instances * multimesh->stride_cache * sizeof(float)), data, GL_STATIC_DRAW);
+					glBufferSubData(GL_ARRAY_BUFFER, 0, MIN(visible_region_count * region_size, multimesh->instances * multimesh->stride_cache * sizeof(float)), data);
 					glBindBuffer(GL_ARRAY_BUFFER, 0);
 				} else {
 					// Not that many regions? update them all

servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp

@@ -1805,8 +1805,12 @@ void MeshStorage::multimesh_set_visible_instances(RID p_multimesh, int p_visible
 	}
 
 	if (multimesh->data_cache.size()) {
-		//there is a data cache..
+		// There is a data cache, but we may need to update some sections.
 		_multimesh_mark_all_dirty(multimesh, false, true);
+		int start = multimesh->visible_instances >= 0 ? multimesh->visible_instances : multimesh->instances;
+		for (int i = start; i < p_visible; i++) {
+			_multimesh_mark_dirty(multimesh, i, true);
+		}
 	}
 
 	multimesh->visible_instances = p_visible;

servers/rendering/renderer_scene_cull.h

@@ -485,6 +485,7 @@ public:
 					singleton->_instance_queue_update(instance, true, false);
 
 				} break;
+				case Dependency::DEPENDENCY_CHANGED_MULTIMESH_VISIBLE_INSTANCES:
 				case Dependency::DEPENDENCY_CHANGED_MATERIAL: {
 					singleton->_instance_queue_update(instance, false, true);
 				} break;
@@ -496,9 +497,6 @@ public:
 				case Dependency::DEPENDENCY_CHANGED_REFLECTION_PROBE: {
 					singleton->_instance_queue_update(instance, true, true);
 				} break;
-				case Dependency::DEPENDENCY_CHANGED_MULTIMESH_VISIBLE_INSTANCES: {
-					//ignored
-				} break;
 				case Dependency::DEPENDENCY_CHANGED_LIGHT_SOFT_SHADOW_AND_PROJECTOR: {
 					//requires repairing
 					if (instance->indexer_id.is_valid()) {