Interesting question, especially if you try to port some Shadertoy demos that can read the keyboard from the pixel shader.
If you need to draw few lines with GeeXLab, this article should help you.
GeeXLab 0.9.x.x is available with Lua 5.3 and one of the new features of Lua 5.3 is the native support of 64-bit integer numbers. In previous versions of Lua, only double precision floating numbers were available (fp64).
If you need to retrieve date and time in Lua, here is small demo that displays the current date as well as elapsed time in seconds.
In recent versions of GeeXLab, I added the support of reflections (mirror, surface water for example). Here is how to do a reflection with GeeXLab:
It may be useful to know if the current OpenGL implementation supports a particular OpenGL extension. For example you have coded a cool OpenGL 4.0 demo based on tessellation shaders. It would be nice to display a different scene (actually an error scene) if the demo runs on a system that is limited to OpenGL 3.0.
Remark: in the following article, words GLSL Hacker and GeeXLab are swappable! They represent the same software with a different name…
Today we are going to see how to build and render a simple scene that includes a camera, a triangle, a reference grid and a GPU program (in GLSL). GLSL Hacker supports both Lua and Python programming languages. We will use Lua for this article. So let’s go!
I didn’t checked all possible use cases of GLSL Hacker (a huge and actually impossible task) and some sequences of drawing instructions (render calls) can generate OpenGL errors. So if you suspect something dodgy because the rendering is not what you expect, you can check the OpenGL errors after some particular instructions.