PingPong Buffer Shader Problem in ofxShader

Hi there,

I’m trying to get this slitscan shader by patriciogonzalezvivo to work on my rpi3b+:

In this example the ping pong buffers are handled in the ofApp.cpp file and the shader code is in the setup function via STRINGIFY.
I tried to get this working using STRINGIFY but had no luck.

So, I’m now trying to use the feedback technique from ofxShader where the ping pong buffers are handled in the .frag file.
I’ve already used this technique to get a shadertoy feedback shader and it worked completely fine.

From what I can tell, I’ve written the code for the slitscan shader the same way as I did with the shadertoy shader but I’m getting nowhere and have run out of ways to troubleshoot this problem.

Does anyone have any thoughts on what might be going wrong? I’m happy to share my code if that will help.

I’ve read quite a bit on the forum about getting shaders working on the rpi and think I’m following most of the advice but I must be going wrong somewhere…