XRWebGLBinding: getViewSubImage() 方法

getViewSubImage(layer, view)

const xrGlBinding = new XRWebGLBinding(xrSession, gl);
const layer = xrGlBinding.createProjectionLayer({});
const framebuffer = gl.createFramebuffer();

xrSession.updateRenderState({ layers: [layer] });
xrSession.requestAnimationFrame(onXRFrame);

function onXRFrame(time, xrFrame) {
  xrSession.requestAnimationFrame(onXRFrame);

  gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);

  for (const view in xrViewerPose.views) {
    const subImage = xrGlBinding.getViewSubImage(layer, view);
    gl.framebufferTexture2D(
      gl.FRAMEBUFFER,
      gl.COLOR_ATTACHMENT0,
      gl.TEXTURE_2D,
      subImage.colorTexture,
      0,
    );
    gl.framebufferTexture2D(
      gl.FRAMEBUFFER,
      gl.DEPTH_ATTACHMENT,
      gl.TEXTURE_2D,
      subImage.depthStencilTexture,
      0,
    );
    const viewport = subImage.viewport;
    gl.viewport(viewport.x, viewport.y, viewport.width, viewport.height);

    // Render from the viewpoint of xrView
  }
}