如何在three.j中实现ShaderToy着色器?

looking for info on how to recreate the ShaderToy parameters iGlobalTime, iChannel etc within threejs. I know that iGlobalTime is the time elapsed since the Shader started, and I think the iChannel stuff is for pulling rgb out of textures, but would appreciate info on how to set these.looking for info on how to recreate the ShaderT