CubeGenerator

import gfx.genmesh.algorithm;
import std.algorithm : map, each, equal;
import std.stdio;

struct Vertex {
    float[3] pos;
    float[3] normal;
    float[2] texCoord;
}
auto cube = genCube()                               // faces of internal vertex type
        .vertexMap!((v) {
            return typeof(v)([2*v.p[0], 2*v.p[1], 2*v.p[2]], v.n);
        })                                          // same face type with a transform (scaled by 2)
        .map!(f => quad(
            Vertex(f[0].p, f[0].n, [0f, 0f]),
            Vertex(f[1].p, f[1].n, [0f, 1f]),
            Vertex(f[2].p, f[2].n, [1f, 1f]),
            Vertex(f[3].p, f[3].n, [1f, 0f]),
        ))                                          // faces with application vertex type (tex coord added)
        .triangulate()                              // triangular faces (with app vertex type)
        .vertices()                                 // application vertices
        .indexCollectMesh();                        // mesh type with array members "indices" and "vertices"

// only the last step actually pull and transform the data all along the chain

foreach (f; 0 .. 6) {
    immutable f6 = f*6;
    immutable f4 = f*4;
    assert(cube.indices[f6 .. f6+6].equal([f4, f4+1, f4+2, f4, f4+2, f4+3]));
}