925df10ad0
is the same as an arg matrix. LGTM=crawshaw R=crawshaw CC=golang-codereviews https://golang.org/cl/152850043
56 lines
1.3 KiB
Go
56 lines
1.3 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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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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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 stores a × b in m.
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func (m *Affine) Mul(a, b *Affine) {
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// Store the result in local variables, in case m == a || m == b.
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m00 := a[0][0]*b[0][0] + a[0][1]*b[1][0]
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m01 := a[0][0]*b[0][1] + a[0][1]*b[1][1]
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m02 := a[0][0]*b[0][2] + a[0][1]*b[1][2] + a[0][2]
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m10 := a[1][0]*b[0][0] + a[1][1]*b[1][0]
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m11 := a[1][0]*b[0][1] + a[1][1]*b[1][1]
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m12 := a[1][0]*b[0][2] + a[1][1]*b[1][2] + a[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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