103 lines
2.1 KiB
Go
103 lines
2.1 KiB
Go
package gg
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import (
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"math"
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"github.com/hajimehoshi/ebiten/v2"
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)
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type EVertex = ebiten.Vertex
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// Ebitens vector in better abstractions like Vectors.
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type Vertex struct {
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Dst Vector
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Src Vector
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Colority
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}
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type Triangle [3]Vector
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type Triangles []Triangle
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type DrawableTriangles struct {
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Triangles
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Colority
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}
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func (v Vertex) Ebiten() EVertex {
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return EVertex {
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DstX: float32(v.Dst.X),
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DstY: float32(v.Dst.Y),
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SrcX: float32(v.Src.X),
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SrcY: float32(v.Src.Y),
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ColorR: float32(v.Color.R)/(float32(MaxColorV)),
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ColorG: float32(v.Color.G)/(float32(MaxColorV)),
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ColorB: float32(v.Color.B)/(float32(MaxColorV)),
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ColorA: float32(v.Color.A)/(float32(MaxColorV)),
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}
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}
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// Returns the area of the triangle.
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func (t Triangle) Area() Float {
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x1 := t[0].X
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y1 := t[0].Y
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x2 := t[1].X
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y2 := t[1].Y
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x3 := t[2].X
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y3 := t[2].Y
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return math.Abs( (x1*(y2-y3) + x2*(y3-y1) + x3*(y1-y2))/2)
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}
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func sqr(v Float) Float {
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return v * v
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}
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// Return squares of lengths of sides of the triangle.
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func (t Triangle) SideLengthSquares() ([3]Float) {
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l1 := LineSegment{t[0], t[1]}.LenSqr()
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l2 := LineSegment{t[1], t[2]}.LenSqr()
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l3 := LineSegment{t[2], t[0]}.LenSqr()
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return [3]Float{l1, l2, l3}
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}
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// Check whether the point is in the triangle.
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func (t Triangle) ContainsPoint(p Point) bool {
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d1 := Triangle{p, t[0], t[1]}.Sgn()
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d2 := Triangle{p, t[1], t[2]}.Sgn()
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d3 := Triangle{p, t[2], t[0]}.Sgn()
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neg := (d1 < 0) || (d2 < 0) || (d3 < 0)
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pos := (d1 > 0) || (d2 > 0) || (d3 > 0)
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return !(neg && pos)
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}
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func (t Triangle) Sgn() Float {
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return (t[0].X - t[2].X) * (t[1].Y - t[2].Y) -
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(t[1].X - t[2].X) * (t[0].Y - t[2].Y)
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}
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func (ts Triangles) ContainsPoint(p Point) bool {
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for _, t := range ts {
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if t.ContainsPoint(p) {
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return true
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}
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}
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return false
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}
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func (r *DrawableTriangles) MakeEVertices(c *Context) []EVertex {
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m := c.Camera.RealMatrix()
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vs := make([]ebiten.Vertex, len(r.Triangles) * 3)
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var buf Vertex
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buf.Color = r.Color
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for i := range r.Triangles {
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for j := range r.Triangles[i] {
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buf.Dst = r.Triangles[i][j].Apply(m)
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vs[i*3 + j] = buf.Ebiten()
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}
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}
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return vs
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}
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