preprocessor ifdef elseifdef?

[Pryme8]

How would one go about completing this logic:
I need to do elseif statments for the defines.

float n0;
    #ifdef STONEFLOOR
        n0 = 1.0;
    #elseif WOOD

    #else
        //Base Stone
        n0 = abs(noise2((nUV*16.0)+fbm2((vUV-vec2(23333.222,3333.22))*32.0)*2.0-1.0));
    #endif


    vec3 color;

    #ifdef SPECULAR
        color = mix(vec3(0.1), vec3(0.72), n0);
    #elseif BUMP
        color = mix(vec3(0.0), vec3(0.7), n0);  
    #else
        #ifdef STONEFLOOR
            color = vec3(1.0);
        #elseif WOOD

        #else
            //Base Stone
            color = mix(vec3(0.4, 0.4, 0.42), vec3(0.6, 0.65, 0.65), n0);
        #endif        
    #endif

    gl_FragColor = vec4(color, 1.0);

I was going off of :http://www.people.vcu.edu/~jsiebers/mcnpinfo/dcomment/manual/node9.html
& https://www.khronos.org/registry/OpenGL/specs/gl/GLSLangSpec.4.50.pdf

[brianzinn]

#ifdef VAR1
  ...
#endif

#ifndef VAR1
#endif
Not very pretty, but I haven't seen else...  you can nest those as well.
https://github.com/BabylonJS/Babylon.js/blob/master/src/Shaders/pbr.vertex.fx#L149

[brianzinn]

actually, I see that you have #elseif and then #else preprocessors.  I think you need to use defined() function and boolean logic.

[Pryme8]

funny part is I just figured that out right before I read your post and was gonna try that.

You just reinforced that I should give that a shot, THANKS!


#if defined(BLAH)
#elif defined(BLAH2)
#endif 

right?

[brianzinn]

Did you try elif?
#if #ifdef #ifndef #else #elif #endif
 

https://www.khronos.org/registry/OpenGL/specs/gl/GLSLangSpec.1.20.pdf
think they just copied c (https://en.wikipedia.org/wiki/C_preprocessor)

[Pryme8]

❤️

 

float n0;

#if defined(STONEFLOOR)

n0 = 1.0;

#elif defined(WOOD)

n0 = 1.0;

#else

//Base Stone

n0 = abs(noise2((nUV*16.0)+fbm2((vUV-vec2(23333.222,3333.22))*32.0)*2.0-1.0));

#endif

 

vec3 color = vec3(0.);

#if defined(SPECULAR)

color = mix(vec3(0.1), vec3(0.72), n0);

#elif defined(BUMP)

color = mix(vec3(0.0), vec3(0.7), n0);

#else

#if defined(STONEFLOOR)

color = vec3(1.0);

#elif defined(WOOD)

color = vec3(1.0);

#else

//Base Stone

color = mix(vec3(0.4, 0.4, 0.42), vec3(0.6, 0.65, 0.65), n0);

#endif

#endif

 

gl_FragColor = vec4(color, 1.0);

[Nabroski]

This is called a shader permutation hell. Babylonjs is master of this technique and it has understandable reasons (more or less), that's not the point. Think over it. Are you really winning something ? The compiler still needs to hold the hole damn thing in his register in order to throw and error exception. In worst case you end with something like this, scroll down, yes a bit longer, do you notice something. It's 2018 we not in C/C++ DX Engine, WebGL relies on Javascript, when you look closer at you shader, it is just a simple string, - manipulate the s t r i n g not the shader. 

[Pryme8]

that is an interesting concept @Nabroski I like where your head is going.

I had a similar concept as what you are talking about that was trying to make a raymarching engine that edited the shader string like you are mentioning.  

I see pro's and con's to both and definitively see each as a valid method givin certain problems