Hi,
I have been playing around with the following example

http://processing.org/learning/topics/convolution.html

the example sharpens the image withing a square area centered on mouseX & mouseY.
In P2D & P3D, the image refreshes back to the original image once the square area has passed over.
Can someone explain to me why when using openGL the image does not refresh back to the original image?

The following discussion touches on the same problem i think.
https://forum.processing.org/topic/screen-fading-code-doesn-t-work-in-opengl


Thanks