fresnel | SSR compatible approach to CSS media query | Frontend Framework library

I think you'll need to make a library from the C source files you referenced. They aren't sufficiently self-contained as they are.

I would suggest structuring your build to compile the .c source files along with your own application sources, and linking the whole lot into an executable. You'll need to extract the function declarations from each of the .c files and put them into a .h header. You'd #include that header in your own source, and probably in the .c files unless you want a screen-full of compiler warnings each time you compile.

You'll need to decide whether to compile the .c files as ordinary C, or rename them and compile them as C++. You might have to modify them, for a C++ compiler to compile them without complaint. If you keep them as C, you'll need to arrange for these files to be compiled as C, and your own as C++. So the headers you make will need to be compatible with both C and C++ -- there are standard techniques for this, which I could advise on (but there's probably stuff on SO already).

If this were my problem to solve, I'd consider combining all the .c files into a single file, and fiddle it to be good C++ (probably not difficult). I'd create one single header from the declarations in the C source, suitable for including in C++ source (since it's all C++ now). However, I'm not sure whether the original files are licensed in such a way to allow this -- that's something I guess you'd need to check with the author.

You may use UNION with your provided select statements

I am not sure if your current code is correct. I wrote a short script to interpolate Euler spirals using similar parameters and it gives different results:

So, the part you want to change is the section involving rim:

The #pragma multi_compile WATER_REFRACTIVE WATER_REFLECTIVE WATER_SIMPLE line allows the script to have different modes depending on global configuration. From the documentation:

How multi_compile works

Example directive:

There are 2 function declarations in the middle of the function BRDF. This is not allowed. In GLSL a function definition has to be global.

See GLSL - The OpenGL Shading Language 4.6; 6.1. Function Definitions ; page 122:

As indicated by the grammar above, a valid shader is a sequence of global declarations and function definitions.

Move the declarations of Fresnel and ggx_visib before the declaration of BRDF to solve your issue.

The major issue is, that the BRDF explorer requires the keyword analytic at the begin of the file, to identify the file as a light model.

After the keyword is add add the file reloaded, the application will trace error cause by your GLSL code.

Fixing the errors results in the following code:

If it's not important to write your own Simpon's Rule, then you can use the import from scipy.integrate import simps. The following code is an attempt at your problem:

The tangent and the biTangent have to be transformed by the normal matrix as you do it with the normal vector:

As discussed in the comments, minimize seems to be more appropriate for this kind of problem. The following works and terminates successfully: