Thank you for your example files, Emil. Those are appreciated. I did not promote and set the "ogl_glsl_shader" rendering property of the geometry's material to display my GLSL shader. But instead, I created a new SHOP type (Network type: GLSL shader) via File > New Asset... and directly assigned an instance of said type to my geometry. Seems to work. I still have a couple of questions though: - Which approach should be preferred ("ogl_glsl_shader" vs. new SHOP type) and why? - And how are my GLSL shaders supposed to blend with Houdini's natural lighting computations? The doc recommends the use of built-in functions such as HOUassignLitOutput() (cf. http://www.sidefx.com/docs/houdini/shade/glsl.html#houdini-built-in-functions), but I could not make it work properly. When creating a new SHOP type, Houdini provides me with a default implementation for the fragment shader which involves the HOUassignOutputs() function. However, no matter how I try to edit its call, my geometry always appears completely flat (and so does Houdini's default GLSL shader). Any help is welcome. Cheers.