resetShaderPassStacks() {
        // now rebuild the drawStacks
        // start by clearing all drawstacks
        this.stacks.scenePasses = [];
        this.stacks.renderPasses = [];

        // restack our planes with new indexes
        for(let i = 0; i < this.renderer.shaderPasses.length; i++) {
            this.renderer.shaderPasses[i].index = i;
            if(this.renderer.shaderPasses[i]._isScenePass) {
                this.stacks.scenePasses.push(this.renderer.shaderPasses[i]);
            }
            else {
                this.stacks.renderPasses.push(this.renderer.shaderPasses[i]);
            }
        }

        // reset the scenePassIndex if needed
        if(this.stacks.scenePasses.length === 0) {
            this.renderer.state.scenePassIndex = null;
        }
    }
Reset the shader pass stacks (used when disposing a shader pass)
*