How to use signal history in spark ar?

问题

I'm trying to display the delayed image from the camera:

material0.setTextureSlot(Shaders.DefaultMaterialTextures.DIFFUSE, cameraTexture0.signal.history(1)[0]);

but it's not working :( There is only white color on material0.

Can you please help me with that?

来源：https://stackoverflow.com/questions/63989984/how-to-use-signal-history-in-spark-ar