tofu.js/src/postprocessing/MaskPass.js

a helper three.js library for building UC-AR

import Pass from './Pass';

/**
 * @author alteredq / http://alteredqualia.com/
 * @private
 */
export default class MaskPass extends Pass {
  constructor(scene, camera) {
    super();
    this.scene = scene;
    this.camera = camera;

    this.clear = true;
    this.needsSwap = false;
    this.inverse = false;
  }

  render(renderer, writeBuffer, readBuffer) {

    const context = renderer.context;
    const state = renderer.state;

    // don't update color or depth

    state.buffers.color.setMask(false);
    state.buffers.depth.setMask(false);

    // lock buffers

    state.buffers.color.setLocked(true);
    state.buffers.depth.setLocked(true);

    // set up stencil

    let writeValue;
    let clearValue;

    if (this.inverse) {

      writeValue = 0;
      clearValue = 1;

    } else {

      writeValue = 1;
      clearValue = 0;

    }

    state.buffers.stencil.setTest(true);
    state.buffers.stencil.setOp(context.REPLACE, context.REPLACE, context.REPLACE);
    state.buffers.stencil.setFunc(context.ALWAYS, writeValue, 0xffffffff);
    state.buffers.stencil.setClear(clearValue);

    // draw into the stencil buffer

    renderer.render(this.scene, this.camera, readBuffer, this.clear);
    renderer.render(this.scene, this.camera, writeBuffer, this.clear);

    // unlock color and depth buffer for subsequent rendering

    state.buffers.color.setLocked(false);
    state.buffers.depth.setLocked(false);

    // only render where stencil is set to 1

    state.buffers.stencil.setFunc(context.EQUAL, 1, 0xffffffff); // draw if == 1
    state.buffers.stencil.setOp(context.KEEP, context.KEEP, context.KEEP);

  }

}