mirror of https://github.com/tidwall/tile38.git
100 lines
2.1 KiB
Go
100 lines
2.1 KiB
Go
package geometry
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import "math"
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// RaycastResult holds the results of the Raycast operation
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type RaycastResult struct {
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In bool // point on the left
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On bool // point is directly on top of
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}
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// Raycast performs the raycast operation
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func (seg Segment) Raycast(point Point) RaycastResult {
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p, a, b := point, seg.A, seg.B
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// make sure that the point is inside the segment bounds
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if a.Y < b.Y && (p.Y < a.Y || p.Y > b.Y) {
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return RaycastResult{false, false}
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} else if a.Y > b.Y && (p.Y < b.Y || p.Y > a.Y) {
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return RaycastResult{false, false}
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}
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// test if point is in on the segment
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if a.Y == b.Y {
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if a.X == b.X {
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if p == a {
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return RaycastResult{false, true}
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}
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return RaycastResult{false, false}
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}
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if p.Y == b.Y {
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// horizontal segment
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// check if the point in on the line
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if a.X < b.X {
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if p.X >= a.X && p.X <= b.X {
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return RaycastResult{false, true}
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}
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} else {
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if p.X >= b.X && p.X <= a.X {
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return RaycastResult{false, true}
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}
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}
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}
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}
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if a.X == b.X && p.X == b.X {
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// vertical segment
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// check if the point in on the line
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if a.Y < b.Y {
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if p.Y >= a.Y && p.Y <= b.Y {
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return RaycastResult{false, true}
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}
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} else {
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if p.Y >= b.Y && p.Y <= a.Y {
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return RaycastResult{false, true}
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}
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}
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}
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if (p.X-a.X)/(b.X-a.X) == (p.Y-a.Y)/(b.Y-a.Y) {
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return RaycastResult{false, true}
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}
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// do the actual raycast here.
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for p.Y == a.Y || p.Y == b.Y {
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p.Y = math.Nextafter(p.Y, math.Inf(1))
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}
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if a.Y < b.Y {
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if p.Y < a.Y || p.Y > b.Y {
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return RaycastResult{false, false}
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}
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} else {
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if p.Y < b.Y || p.Y > a.Y {
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return RaycastResult{false, false}
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}
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}
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if a.X > b.X {
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if p.X >= a.X {
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return RaycastResult{false, false}
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}
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if p.X <= b.X {
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return RaycastResult{true, false}
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}
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} else {
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if p.X >= b.X {
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return RaycastResult{false, false}
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}
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if p.X <= a.X {
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return RaycastResult{true, false}
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}
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}
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if a.Y < b.Y {
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if (p.Y-a.Y)/(p.X-a.X) >= (b.Y-a.Y)/(b.X-a.X) {
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return RaycastResult{true, false}
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}
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} else {
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if (p.Y-b.Y)/(p.X-b.X) >= (a.Y-b.Y)/(a.X-b.X) {
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return RaycastResult{true, false}
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}
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}
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return RaycastResult{false, false}
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}
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