only call renderBlendedTransparent when needed

src/mol-canvas3d/passes/draw.ts

@@ -230,8 +230,10 @@ export class DrawPass {
             }
         }
 
+        if (scene.opacityAverage < 1) {
             renderer.renderBlendedTransparent(scene.primitives, camera, null);
         }
+    }
 
     private _render(renderer: Renderer, camera: ICamera, scene: Scene, helper: Helper, toDrawingBuffer: boolean, props: Props) {
         const volumeRendering = scene.volumes.renderables.length > 0;