blit threejs framebuffer / renderTarget

blit.ts

function blit(renderer: WebGLRenderer, source: WebGLRenderTarget, dest: WebGLRenderTarget) {
  const gl = renderer.getContext() as WebGL2RenderingContext;
  const prop = renderer.properties;
  const readBuffer = (prop.get(source) as any).__webglFramebuffer;
  const readTexture = (prop.get(source.texture) as any).__webglTexture;
  const writeBuffer = (prop.get(dest) as any).__webglFramebuffer;
  const writeTexture = (prop.get(dest.texture) as any).__webglTexture;

  gl.bindFramebuffer(gl.READ_FRAMEBUFFER, readBuffer);
  gl.framebufferTexture2D(gl.READ_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, readTexture, 0);
  gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, writeBuffer);
  gl.framebufferTexture2D(gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, writeTexture, 0);
  gl.blitFramebuffer(
    0,
    0,
    source.width,
    source.height,
    0,
    0,
    source.width,
    source.height,
    gl.COLOR_BUFFER_BIT,
    gl.NEAREST,
  );
  gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
  gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
}