The documentation says it is possible, https://www.sidefx.com/docs/houdini/shade/glsl.html [www.sidefx.com]

I found a nice website stepping through the steps, https://serano-vfx-lab.hatenablog.com/entry/2020/05/11/160807 [serano-vfx-lab.hatenablog.com]

I followed and did everything exactly the same, but, it does not work. Attached is a very simple scene file and HDA, I edited the fragment shader, on line 243, I hardcode tex to be a bright purple:

tex = vec4(1.0, 0.0, 1.0, 1.0);

and it does nothing. It's shown working in the tutorial. Perhaps there was a change in the viewport since this tutorial? I don't see a lot of mention of glsl work being done,might it be broken in version 21.0.440? Is there a step I am missing?

Are you sure you're running an OpenGL based viewport and not Vulkan one? This only works in opengl.

Hey! That worked!!

indeed, it was a vulkan viewport, when I switched there is a note that openGL viewport is deprecated.

It works, I can play around now, life is good.

However, will the option to use custom GLSL in the viewport be gone forever when the deprecated viewport is removed?