geom/lin/projection32.go

package lin

import "opslag.de/schobers/geom"

func basisToPoints(p1, p2, p3, p4 geom.PointF32) geom.Matrix3x3F32 {
	var m = geom.Mx3x3F32(geom.Vec3F32(p1.X, p1.Y, 1), geom.Vec3F32(p2.X, p2.Y, 1), geom.Vec3F32(p3.X, p3.Y, 1))
	var v = m.Adj().MulVec(geom.Vec3F32(p4.X, p4.Y, 1))
	return m.MulMx(geom.Mx3x3F32(geom.Vec3F32(v.X, 0, 0), geom.Vec3F32(0, v.Y, 0), geom.Vec3F32(0, 0, v.Z)))
}

// Projection32 calculates the projection matrix to transformation a point in rectangle src1, src2, src3, src4 to a point in rectangle dst1, dst2, dst3 and dst4.
func Projection32(src1, dst1, src2, dst2, src3, dst3, src4, dst4 geom.PointF32) geom.Matrix3x3F32 {
	var s = basisToPoints(src1, src2, src3, src4)
	var d = basisToPoints(dst1, dst2, dst3, dst4)
	return d.MulMx(s.Adj())
}

// Project32 projects a point pt using the projection matrix p and returns the resulting point.
func Project32(p geom.Matrix3x3F32, pt geom.PointF32) geom.PointF32 {
	var res = p.MulVec(geom.Vec3F32(pt.X, pt.Y, 1))
	return geom.PtF32(res.X/res.Z, res.Y/res.Z)
}