Adding upstream version 0.0~git20250520.a1d9079+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

exp/f32/affine.go

@@ -0,0 +1,109 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package f32
+
+import "fmt"
+
+// An Affine is a 3x3 matrix of float32 values for which the bottom row is
+// implicitly always equal to [0 0 1].
+// Elements are indexed first by row then column, i.e. m[row][column].
+type Affine [2]Vec3
+
+func (m Affine) String() string {
+	return fmt.Sprintf(`Affine[% 0.3f, % 0.3f, % 0.3f,
+     % 0.3f, % 0.3f, % 0.3f]`,
+		m[0][0], m[0][1], m[0][2],
+		m[1][0], m[1][1], m[1][2])
+}
+
+// Identity sets m to be the identity transform.
+func (m *Affine) Identity() {
+	*m = Affine{
+		{1, 0, 0},
+		{0, 1, 0},
+	}
+}
+
+// Eq reports whether each component of m is within epsilon of the same
+// component in n.
+func (m *Affine) Eq(n *Affine, epsilon float32) bool {
+	for i := range m {
+		for j := range m[i] {
+			diff := m[i][j] - n[i][j]
+			if diff < -epsilon || +epsilon < diff {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// Mul sets m to be p × q.
+func (m *Affine) Mul(p, q *Affine) {
+	// Store the result in local variables, in case m == a || m == b.
+	m00 := p[0][0]*q[0][0] + p[0][1]*q[1][0]
+	m01 := p[0][0]*q[0][1] + p[0][1]*q[1][1]
+	m02 := p[0][0]*q[0][2] + p[0][1]*q[1][2] + p[0][2]
+	m10 := p[1][0]*q[0][0] + p[1][1]*q[1][0]
+	m11 := p[1][0]*q[0][1] + p[1][1]*q[1][1]
+	m12 := p[1][0]*q[0][2] + p[1][1]*q[1][2] + p[1][2]
+	m[0][0] = m00
+	m[0][1] = m01
+	m[0][2] = m02
+	m[1][0] = m10
+	m[1][1] = m11
+	m[1][2] = m12
+}
+
+// Inverse sets m to be the inverse of p.
+func (m *Affine) Inverse(p *Affine) {
+	m00 := p[1][1]
+	m01 := -p[0][1]
+	m02 := p[1][2]*p[0][1] - p[1][1]*p[0][2]
+	m10 := -p[1][0]
+	m11 := p[0][0]
+	m12 := p[1][0]*p[0][2] - p[1][2]*p[0][0]
+
+	det := m00*m11 - m10*m01
+
+	m[0][0] = m00 / det
+	m[0][1] = m01 / det
+	m[0][2] = m02 / det
+	m[1][0] = m10 / det
+	m[1][1] = m11 / det
+	m[1][2] = m12 / det
+}
+
+// Scale sets m to be a scale followed by p.
+// It is equivalent to m.Mul(p, &Affine{{x,0,0}, {0,y,0}}).
+func (m *Affine) Scale(p *Affine, x, y float32) {
+	m[0][0] = p[0][0] * x
+	m[0][1] = p[0][1] * y
+	m[0][2] = p[0][2]
+	m[1][0] = p[1][0] * x
+	m[1][1] = p[1][1] * y
+	m[1][2] = p[1][2]
+}
+
+// Translate sets m to be a translation followed by p.
+// It is equivalent to m.Mul(p, &Affine{{1,0,x}, {0,1,y}}).
+func (m *Affine) Translate(p *Affine, x, y float32) {
+	m[0][0] = p[0][0]
+	m[0][1] = p[0][1]
+	m[0][2] = p[0][0]*x + p[0][1]*y + p[0][2]
+	m[1][0] = p[1][0]
+	m[1][1] = p[1][1]
+	m[1][2] = p[1][0]*x + p[1][1]*y + p[1][2]
+}
+
+// Rotate sets m to a rotation in radians followed by p.
+// It is equivalent to m.Mul(p, affineRotation).
+func (m *Affine) Rotate(p *Affine, radians float32) {
+	s, c := Sin(radians), Cos(radians)
+	m.Mul(p, &Affine{
+		{+c, +s, 0},
+		{-s, +c, 0},
+	})
+}