67 lines
1.3 KiB
Go
67 lines
1.3 KiB
Go
package mathx
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type Mat3 [9]float32
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func Mat3Identity() Mat3 {
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return Mat3{1, 0, 0, 0, 1, 0, 0, 0, 1}
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}
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func Mat3TRS(pos Vec2, rad float32, scale Vec2) Mat3 {
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c, s := Cos(rad), Sin(rad)
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return Mat3{
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c * scale.X, s * scale.X, 0,
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-s * scale.Y, c * scale.Y, 0,
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pos.X, pos.Y, 1,
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}
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}
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func (m Mat3) Mul(o Mat3) Mat3 {
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var r Mat3
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for c := 0; c < 3; c++ {
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for row := 0; row < 3; row++ {
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var sum float32
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for k := 0; k < 3; k++ {
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sum += m[k*3+row] * o[c*3+k]
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}
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r[c*3+row] = sum
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}
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}
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return r
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}
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func (m Mat3) Apply(p Vec2) Vec2 {
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return Vec2{
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X: m[0]*p.X + m[3]*p.Y + m[6],
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Y: m[1]*p.X + m[4]*p.Y + m[7],
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}
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}
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func (m Mat3) ApplyVector(v Vec2) Vec2 {
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return Vec2{
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X: m[0]*v.X + m[3]*v.Y,
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Y: m[1]*v.X + m[4]*v.Y,
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}
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}
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func (m Mat3) Inverse() (Mat3, bool) {
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a := m
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det := a[0]*(a[4]*a[8]-a[5]*a[7]) -
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a[1]*(a[3]*a[8]-a[5]*a[6]) +
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a[2]*(a[3]*a[7]-a[4]*a[6])
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if Abs(det) < 1e-20 {
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return Mat3Identity(), false
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}
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inv := 1 / det
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return Mat3{
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(a[4]*a[8] - a[5]*a[7]) * inv,
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(a[2]*a[7] - a[1]*a[8]) * inv,
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(a[1]*a[5] - a[2]*a[4]) * inv,
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(a[5]*a[6] - a[3]*a[8]) * inv,
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(a[0]*a[8] - a[2]*a[6]) * inv,
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(a[2]*a[3] - a[0]*a[5]) * inv,
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(a[3]*a[7] - a[4]*a[6]) * inv,
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(a[1]*a[6] - a[0]*a[7]) * inv,
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(a[0]*a[4] - a[1]*a[3]) * inv,
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}, true
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}
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