model.shadron

#include <math_constants>
#include <affine_transform>
#include <lighting>

param int sides = 3 : logrange(3, 12);
param float zRotation : range(-PI, PI);
param float xRotation : range(-PI, PI);

glsl struct FragmentData {
    vec3 normal;
    vec4 color;
};

glsl vec3 crystalCoord(int index) {
    int triangle = index/3;
    index %= 3;
    vec3 coord;
    if (index == 0) {
        coord = vec3(0.0, 0.0, 1.0);
    }
    if (index == 1) {
        float a = TAU*float(triangle)/float(sides);
        coord = 0.5*vec3(sin(a), cos(a), 0.0);
    }
    if (index == 2) {
        float a = TAU*float(triangle - 1)/float(sides);
        coord = 0.5*vec3(sin(a), cos(a), 0.0);
    }
    if (triangle >= sides)
        coord.xz *= -1.0;
    return coord;
}

glsl vec3 crystalNormal(int index) {
    int triangle = index/3;
    vec3 a = crystalCoord(3*triangle + 0);
    vec3 b = crystalCoord(3*triangle + 1);
    vec3 c = crystalCoord(3*triangle + 2);
    return normalize(cross(b-a, c-a));
}

glsl vec4 crystalVertex(out FragmentData fd, int index) {
    vec3 coord = crystalCoord(index);

    coord = rotateZ(coord, zRotation);
    coord = rotateX(coord, xRotation);
    coord.z -= 2.5;

    fd.normal = crystalNormal(index);
    fd.color = vec4(1.0, 1.0, 1.0, 1.0);
    return projectPerspectiveHFOV(coord, 0.5*PI, 1.0/256.0, 256.0);
}

glsl vec4 crystalFragment(in FragmentData fd) {
    vec3 lightDirection = normalize(vec3(1.0, 2.0, 3.0));
    float lightIntensity = 0.5 + 0.5*diffuseLight(lightDirection, fd.normal);
    return vec4(lightIntensity * fd.color.rgb, 1.0);
}

model Crystal :
    fragment_data(FragmentData),
    vertex(crystalVertex, triangles, 2*3*sides),
    fragment(crystalFragment),
    wireframe(false), cull(backface),
    multisample(4);