setDepthTest(depthTest) {
        if(depthTest && !this.state.depthTest) {
            this.state.depthTest = depthTest;
            // enable depth test
            this.gl.enable(this.gl.DEPTH_TEST);
        }
        else if(!depthTest && this.state.depthTest) {
            this.state.depthTest = depthTest;
            // disable depth test
            this.gl.disable(this.gl.DEPTH_TEST);
        }
    }
Called to set whether the renderer will handle depth test or not
     Depth test is enabled by default

     params:
     @setDepth (boolean): if we should enable or disable the depth test
*