467d8559f2
In the long term, a lot of this package should be removed in favor of the golang.org/x/image/math/f32 package. The latter is the common location for matrix types shared across graphics libraries. For example, the golang.org/x/image/draw package refers to golang.org/x/image/math/f64. Change-Id: I9d7ccd3cb35912e0d9dc5bd46c919516ea840340 Reviewed-on: https://go-review.googlesource.com/11856 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
110 lines
2.7 KiB
Go
110 lines
2.7 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package f32
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import "fmt"
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// An Affine is a 3x3 matrix of float32 values for which the bottom row is
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// implicitly always equal to [0 0 1].
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// Elements are indexed first by row then column, i.e. m[row][column].
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type Affine [2]Vec3
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func (m Affine) String() string {
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return fmt.Sprintf(`Affine[% 0.3f, % 0.3f, % 0.3f,
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% 0.3f, % 0.3f, % 0.3f]`,
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m[0][0], m[0][1], m[0][2],
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m[1][0], m[1][1], m[1][2])
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}
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// Identity sets m to be the identity transform.
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func (m *Affine) Identity() {
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*m = Affine{
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{1, 0, 0},
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{0, 1, 0},
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}
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}
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// Eq reports whether each component of m is within epsilon of the same
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// component in n.
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func (m *Affine) Eq(n *Affine, epsilon float32) bool {
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for i := range m {
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for j := range m[i] {
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diff := m[i][j] - n[i][j]
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if diff < -epsilon || +epsilon < diff {
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return false
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}
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}
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}
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return true
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}
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// Mul sets m to be p × q.
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func (m *Affine) Mul(p, q *Affine) {
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// Store the result in local variables, in case m == a || m == b.
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m00 := p[0][0]*q[0][0] + p[0][1]*q[1][0]
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m01 := p[0][0]*q[0][1] + p[0][1]*q[1][1]
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m02 := p[0][0]*q[0][2] + p[0][1]*q[1][2] + p[0][2]
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m10 := p[1][0]*q[0][0] + p[1][1]*q[1][0]
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m11 := p[1][0]*q[0][1] + p[1][1]*q[1][1]
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m12 := p[1][0]*q[0][2] + p[1][1]*q[1][2] + p[1][2]
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m[0][0] = m00
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m[0][1] = m01
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m[0][2] = m02
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m[1][0] = m10
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m[1][1] = m11
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m[1][2] = m12
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}
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// Inverse sets m to be the inverse of p.
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func (m *Affine) Inverse(p *Affine) {
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m00 := p[1][1]
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m01 := -p[0][1]
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m02 := p[1][2]*p[0][1] - p[1][1]*p[0][2]
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m10 := -p[1][0]
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m11 := p[0][0]
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m12 := p[1][0]*p[0][2] - p[1][2]*p[0][0]
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det := m00*m11 - m10*m01
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m[0][0] = m00 / det
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m[0][1] = m01 / det
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m[0][2] = m02 / det
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m[1][0] = m10 / det
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m[1][1] = m11 / det
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m[1][2] = m12 / det
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}
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// Scale sets m to be a scale followed by p.
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// It is equivalent to m.Mul(p, &Affine{{x,0,0}, {0,y,0}}).
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func (m *Affine) Scale(p *Affine, x, y float32) {
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m[0][0] = p[0][0] * x
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m[0][1] = p[0][1] * y
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m[0][2] = p[0][2]
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m[1][0] = p[1][0] * x
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m[1][1] = p[1][1] * y
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m[1][2] = p[1][2]
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}
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// Translate sets m to be a translation followed by p.
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// It is equivalent to m.Mul(p, &Affine{{1,0,x}, {0,1,y}}).
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func (m *Affine) Translate(p *Affine, x, y float32) {
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m[0][0] = p[0][0]
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m[0][1] = p[0][1]
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m[0][2] = p[0][0]*x + p[0][1]*y + p[0][2]
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m[1][0] = p[1][0]
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m[1][1] = p[1][1]
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m[1][2] = p[1][0]*x + p[1][1]*y + p[1][2]
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}
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// Rotate sets m to a rotation in radians followed by p.
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// It is equivalent to m.Mul(p, affineRotation).
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func (m *Affine) Rotate(p *Affine, radians float32) {
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s, c := Sin(radians), Cos(radians)
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m.Mul(p, &Affine{
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{+c, +s, 0},
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{-s, +c, 0},
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})
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}
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