MeshTriangle
class MeshTriangle(val x: DoubleArray, val y: DoubleArray, val colors: Array<RgbColor>, val t: DoubleArray? = null)
One Gouraud triangle: three shading-space vertices with colours. In a mesh with a /Function, t holds the parametric value of each vertex. A point inside the triangle then takes its colour from the interpolated t, not from the interpolated colors (ISO 32000-1, 8.7.4.5.5).