CODEWITHSUNDEEP
glslwebglopengl-es-2.0shader
SwagBoy93
SwagBoy93

Reputation: 1

index expression must be constant using array

I would like to apply multiples lights in my shader. To do that, I've make the choice to put lights data in multiple arrays instead of one light = one struct to avoid doing "setUniforms" a lot of time.

I've got something like that:

// Light's data.
struct LightData 
{
   vec3 ambient[4];
   vec3 diffuse[4];
   vec3 position[4];
   vec3 specular[4];
};
uniform LightData lights;


vec3 applyLight( int index, vec3 cameraPos )
{
    vec3 position = lights.position[index]; //<<< Error here.
    …
    return result;
}

int main()
{
    vec3 color;

    for( int i = 0; i < 4; i++)
        color += applyLight(i, camera.position);
}

The problem is in the GLSL code: "index expression must be constant []". How can I do to have this code to work? I could give position, diffuse, ambient, specular to the function but it will by dirty.

What about performances? It is better to have something like what I've done or like the code bellow?

struct Light 
{
   vec3 ambient;
   vec3 diffuse;
   vec3 position;
   vec3 specular;
};
uniform Light lights[4];

Have a nice day!

Upvotes: 0

Views: 2696

Answers (1)

Dragan Okanovic
Dragan Okanovic

Reputation: 7771

Unroll your loop:

color += applyLight(0, camera.position);
color += applyLight(1, camera.position);
color += applyLight(2, camera.position);
color += applyLight(3, camera.position);

(not sure if this exact code will work, but you get the idea)

lights.position[index]; // no
lights.position[0]; // yes, etc

Option below (for uniform layout) might be better, it may have a better locality.

Upvotes: 2

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