[Fluxus] shader array arguments

[Dave Griffiths]

Hi all,

Array arguments are now supported in the hardware shader interface, and
read lists of float, int or vector (size 3 or 4) elements. 

As an example of their use, if you need loads of lights (more than the
OpenGL fixed pipeline 8 light limit) you can do something like this:
http://www.flickr.com/photos/dave-griffiths/3769764975/

(clear)
(clear-shader-cache)

(define nlights 50)
(define pos (build-list nlights (lambda (n) (vadd (vector 0 0 1) (vmul
(srndvec) 3)))))
(define col (build-list nlights (lambda (_) (vmul (rndvec) 2))))
(define falloff (build-list nlights (lambda (_) (* (rndf) 0.3))))

; preview the lights
(for-each 
    (lambda (pos col falloff)
        (with-state
            (translate pos)
            (colour col)
            (scale falloff)
            (hint-unlit)
            (build-sphere 5 5)))
    pos col falloff)
            

(with-state
    (shader-source 
"
varying vec4 P;
varying vec3 N;

void main()
{     
    gl_Position = ftransform();
    P = gl_Vertex;
    N = normalize(gl_NormalMatrix*gl_Normal);
}
" 

"
uniform vec4 LightsPos[50];
uniform vec4 LightsCol[50];
uniform float LightsFalloff[50];
varying vec4 P;
varying vec3 N;

void main()
{
    vec4 final = vec4(0,0,0,1);
    vec3 n = normalize(N);

    for (int i=0; i<10; i++)
    {
        vec4 l=LightsPos[i]-P;
        float d=1.0/length(l)*LightsFalloff[i];
        final+=LightsCol[i]*max(0.0,dot(n,vec3(normalize(l))))*d;
    }

    gl_FragColor = vec4(final.xyz,1);
}
")

    (shader-set! (list 
        "LightsPos" pos
        "LightsCol" col
        "LightsFalloff" falloff
            ))
    
    (build-torus 1 2 20 20))