can't render multi times

[a873054267]

first of all ,Thank you so much for your open source project!
I want to add three-view-drawing on this system;

1 when inital renderer, setting renderer.autoclear = false;
2 add the following code before execute renderer.render in animate function

this.renderer.setViewport(0, 0, 200, 200);
this.renderer.render(this.scene, this.camera);
this.renderer.setViewport(0, 0, this.canvasContainer.clientWidth, this.canvasContainer.clientHeight);

this.renderer.render(this.scene, this.camera);
3 the canvas should exist two render result，but only the last；

4 the above code is correct in my old three project;