func buildCube(mesh *export.Mesh, a, b, c, d uint16) {
A, B, C, D := mesh.Vertices[a].Pos, mesh.Vertices[b].Pos, mesh.Vertices[c].Pos, mesh.Vertices[d].Pos
/* find the center point */
center := A.Add(B).Add(C).Add(D).Mul(float32(0.25))
findMidpoint := func(a, b mathgl.Vec4f) mathgl.Vec4f {
return a.Add(b.Sub(a).Mul(0.5))
}
findMissing := func(a, b, c mathgl.Vec4f) mathgl.Vec4f {
/* Find the midpoints */
var midpoint [3]mathgl.Vec4f
var vert mathgl.Vec4f
midpoint[0] = findMidpoint(a, b)
midpoint[1] = findMidpoint(b, c)
midpoint[2] = findMidpoint(a, c)
/* Find the vertex */
for _, mid := range midpoint {
vert = vert.Add(mid.Sub(center))
}
vert = vert.Add(center)
return vert
}
/* create the missing vertices */
E := findMissing(A, B, C)
F := findMissing(A, D, B)
G := findMissing(A, C, D)
H := findMissing(B, D, C)
/* Create the faces */
mesh.AddVert4f(H)
mesh.AddVert4f(G)
mesh.AddVert4f(F)
mesh.AddVert4f(E)
mesh.AddVert4f(D)
mesh.AddVert4f(C)
mesh.AddVert4f(B)
mesh.AddVert4f(A)
a, b, c, d = mesh.Rel(-1), mesh.Rel(-2), mesh.Rel(-3), mesh.Rel(-4)
e, f, g, h := mesh.Rel(-5), mesh.Rel(-6), mesh.Rel(-7), mesh.Rel(-8)
//traceVerts(mesh, a, b, c, d, e, f, g, h)
mesh.AddFace(types.Tri{a, f, e})
mesh.AddFace(types.Tri{e, f, b})
mesh.AddFace(types.Tri{f, d, b})
mesh.AddFace(types.Tri{d, h, b})
mesh.AddFace(types.Tri{d, g, h})
mesh.AddFace(types.Tri{g, c, h})
mesh.AddFace(types.Tri{g, a, c})
mesh.AddFace(types.Tri{c, a, e})
mesh.AddFace(types.Tri{b, e, c})
mesh.AddFace(types.Tri{b, c, h})
mesh.AddFace(types.Tri{a, f, d})
mesh.AddFace(types.Tri{a, d, g})
}
func traceVerts(mesh *export.Mesh, verts ...uint16) {
if len(verts) < 2 {
panic("not enough verts to trace")
}
for i := 1; i < len(verts); i++ {
mesh.AddVert(mesh.Vertices[verts[i]])
mesh.AddVert(mesh.Vertices[verts[i]])
mesh.AddVert(mesh.Vertices[verts[i-1]])
mesh.AddFace(types.Tri{mesh.Rel(-1), mesh.Rel(-2), mesh.Rel(-3)})
}
}