matrix.go

package MeshTypes

type Matrix struct {
	X00, X01, X02, X03 float64
	X10, X11, X12, X13 float64
	X20, X21, X22, X23 float64
	X30, X31, X32, X33 float64
}

func IdentityMatrix() Matrix {
	return Matrix{
		1, 0, 0, 0,
		0, 1, 0, 0,
		0, 0, 1, 0,
		0, 0, 0, 1,
	}
}

func (a Matrix) Mul(b Matrix) Matrix {
	m := Matrix{}
	m.X00 = a.X00*b.X00 + a.X01*b.X10 + a.X02*b.X20 + a.X03*b.X30
	m.X10 = a.X10*b.X00 + a.X11*b.X10 + a.X12*b.X20 + a.X13*b.X30
	m.X20 = a.X20*b.X00 + a.X21*b.X10 + a.X22*b.X20 + a.X23*b.X30
	m.X30 = a.X30*b.X00 + a.X31*b.X10 + a.X32*b.X20 + a.X33*b.X30
	m.X01 = a.X00*b.X01 + a.X01*b.X11 + a.X02*b.X21 + a.X03*b.X31
	m.X11 = a.X10*b.X01 + a.X11*b.X11 + a.X12*b.X21 + a.X13*b.X31
	m.X21 = a.X20*b.X01 + a.X21*b.X11 + a.X22*b.X21 + a.X23*b.X31
	m.X31 = a.X30*b.X01 + a.X31*b.X11 + a.X32*b.X21 + a.X33*b.X31
	m.X02 = a.X00*b.X02 + a.X01*b.X12 + a.X02*b.X22 + a.X03*b.X32
	m.X12 = a.X10*b.X02 + a.X11*b.X12 + a.X12*b.X22 + a.X13*b.X32
	m.X22 = a.X20*b.X02 + a.X21*b.X12 + a.X22*b.X22 + a.X23*b.X32
	m.X32 = a.X30*b.X02 + a.X31*b.X12 + a.X32*b.X22 + a.X33*b.X32
	m.X03 = a.X00*b.X03 + a.X01*b.X13 + a.X02*b.X23 + a.X03*b.X33
	m.X13 = a.X10*b.X03 + a.X11*b.X13 + a.X12*b.X23 + a.X13*b.X33
	m.X23 = a.X20*b.X03 + a.X21*b.X13 + a.X22*b.X23 + a.X23*b.X33
	m.X33 = a.X30*b.X03 + a.X31*b.X13 + a.X32*b.X23 + a.X33*b.X33
	return m
}

func (a Matrix) MulPosition(b Vector) Vector {
	x := a.X00*b.X + a.X01*b.Y + a.X02*b.Z + a.X03
	y := a.X10*b.X + a.X11*b.Y + a.X12*b.Z + a.X13
	z := a.X20*b.X + a.X21*b.Y + a.X22*b.Z + a.X23
	return Vector{x, y, z}
}

func (a Matrix) MulDirection(b Vector) Vector {
	x := a.X00*b.X + a.X01*b.Y + a.X02*b.Z
	y := a.X10*b.X + a.X11*b.Y + a.X12*b.Z
	z := a.X20*b.X + a.X21*b.Y + a.X22*b.Z
	return Vector{x, y, z}.Normalize()
}