280 lines
6.6 KiB
Go
280 lines
6.6 KiB
Go
package collision
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import (
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"sync"
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"git.kirsle.net/apps/doodle/lib/render"
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"git.kirsle.net/apps/doodle/pkg/doodads"
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"git.kirsle.net/apps/doodle/pkg/level"
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)
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// Collide describes how a collision occurred.
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type Collide struct {
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Top bool
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TopPoint render.Point
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TopPixel *level.Swatch
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Left bool
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LeftPoint render.Point
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LeftPixel *level.Swatch
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Right bool
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RightPoint render.Point
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RightPixel *level.Swatch
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Bottom bool
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BottomPoint render.Point
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BottomPixel *level.Swatch
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MoveTo render.Point
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// Swatch attributes affecting the collision at this time.
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InFire bool
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InWater bool
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}
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// Reset a Collide struct flipping all the bools off, but keeping MoveTo.
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func (c *Collide) Reset() {
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c.Top = false
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c.Left = false
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c.Right = false
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c.Bottom = false
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}
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// Side of the collision box (top, bottom, left, right)
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type Side uint8
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// Options for the Side type.
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const (
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Top Side = iota
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Bottom
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Left
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Right
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)
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/*
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CollidesWithGrid checks if a Doodad collides with level geometry.
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The `target` is the point the actor wants to move to on this tick.
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*/
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func CollidesWithGrid(d doodads.Actor, grid *level.Chunker, target render.Point) (*Collide, bool) {
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var (
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P = d.Position()
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S = d.Size()
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result = &Collide{
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MoveTo: P,
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}
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ceiling bool // Has hit a ceiling?
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capHeight int32 // Stop vertical movement thru a ceiling
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capLeft int32 // Stop movement thru a wall
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capRight int32
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capFloor int32 // Stop movement thru the floor
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hitLeft bool // Has hit an obstacle on the left
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hitRight bool // or right
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hitFloor bool
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)
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// Test all of the bounding boxes for a collision with level geometry.
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if ok := result.ScanBoundingBox(doodads.GetBoundingRect(d), grid); ok {
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// We've already collided! Try to wiggle free.
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if result.Bottom {
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if !d.Grounded() {
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d.SetGrounded(true)
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} else {
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// result.Bottom = false
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}
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} else {
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d.SetGrounded(false)
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}
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if result.Top {
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// Never seen it touch the top.
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}
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if result.Left {
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P.X++
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}
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if result.Right {
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P.X--
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}
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}
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// If grounded, cap our Y position.
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if d.Grounded() {
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if !result.Bottom {
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// We've fallen off a ledge.
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d.SetGrounded(false)
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} else if target.Y < P.Y {
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// We're moving upward.
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d.SetGrounded(false)
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} else {
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// Cap our downward motion to our current position.
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target.Y = P.Y
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}
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}
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// Cap our horizontal movement if we're touching walls.
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if (result.Left && target.X < P.X) || (result.Right && target.X > P.X) {
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// If the step is short enough, try and jump up.
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height := P.Y + S.H
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if result.Left && target.X < P.X {
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height -= result.LeftPoint.Y
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} else {
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height -= result.RightPoint.Y
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}
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if height <= 8 {
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target.Y -= height
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if target.X < P.X {
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target.X-- // push along to the left
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} else if target.X > P.X {
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target.X++ // push along to the right
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}
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} else {
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target.X = P.X
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}
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}
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// Cap our vertical movement if we're touching ceilings.
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if ceiling {
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// The existing box intersects a ceiling, this will almost never
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// happen because gravity will always pull you away at the last frame.
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// But if we do somehow get here, may as well cap it where it's at.
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capHeight = P.Y
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}
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// Trace a line from where we are to where we wanna go.
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result.Reset()
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result.MoveTo = P
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for point := range render.IterLine(P, target) {
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if has := result.ScanBoundingBox(render.Rect{
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X: point.X,
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Y: point.Y,
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W: S.W,
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H: S.H,
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}, grid); has {
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if result.Bottom {
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if !hitFloor {
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hitFloor = true
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capFloor = result.BottomPoint.Y - S.H
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}
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d.SetGrounded(true)
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}
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if result.Top && !ceiling {
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// This is a newly discovered ceiling.
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ceiling = true
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capHeight = result.TopPoint.Y
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}
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if result.Left && !hitLeft {
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hitLeft = true
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capLeft = result.LeftPoint.X
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}
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if result.Right && !hitRight {
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hitRight = true
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capRight = result.RightPoint.X - S.W
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}
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}
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// So far so good, keep following the MoveTo to
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// the last good point before a collision.
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result.MoveTo = point
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}
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// If they hit the roof, cap them to the roof.
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if ceiling && result.MoveTo.Y < capHeight {
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result.Top = true
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result.MoveTo.Y = capHeight
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}
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if hitFloor && result.MoveTo.Y > capFloor {
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result.Bottom = true
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result.MoveTo.Y = capFloor
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}
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if hitLeft {
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result.Left = true
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result.MoveTo.X = capLeft
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}
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if hitRight {
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result.Right = true
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result.MoveTo.X = capRight
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}
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return result, result.IsColliding()
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}
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// IsColliding returns whether any sort of collision has occurred.
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func (c *Collide) IsColliding() bool {
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return c.Top || c.Bottom || c.Left || c.Right ||
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c.InFire || c.InWater
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}
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// ScanBoundingBox scans all of the pixels in a bounding box on the grid and
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// returns if any of them intersect with level geometry.
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func (c *Collide) ScanBoundingBox(box render.Rect, grid *level.Chunker) bool {
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col := GetCollisionBox(box)
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// Check all four edges of the box in parallel on different CPU cores.
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type jobSide struct {
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p1 render.Point // p2 is perpendicular to p1 along a straight edge
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p2 render.Point // of the collision box.
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side Side
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}
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jobs := []jobSide{ // We'll scan each side of the bounding box in parallel
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jobSide{col.Top[0], col.Top[1], Top},
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jobSide{col.Bottom[0], col.Bottom[1], Bottom},
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jobSide{col.Left[0], col.Left[1], Left},
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jobSide{col.Right[0], col.Right[1], Right},
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}
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var wg sync.WaitGroup
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for _, job := range jobs {
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wg.Add(1)
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go func(job jobSide) {
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defer wg.Done()
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c.ScanGridLine(job.p1, job.p2, grid, job.side)
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}(job)
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}
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wg.Wait()
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return c.IsColliding()
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}
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// ScanGridLine scans all of the pixels between p1 and p2 on the grid and tests
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// for any pixels to be set, implying a collision between level geometry and the
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// bounding boxes of the doodad.
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func (c *Collide) ScanGridLine(p1, p2 render.Point, grid *level.Chunker, side Side) {
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for point := range render.IterLine(p1, p2) {
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if swatch, err := grid.Get(point); err == nil {
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// We're intersecting a pixel! If it's a solid one we'll return it
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// in our result. If non-solid, we'll collect attributes from it
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// and return them in the final result for gameplay behavior.
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if swatch.Fire {
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c.InFire = true
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}
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if swatch.Water {
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c.InWater = true
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}
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// Non-solid swatches don't collide so don't pay them attention.
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if !swatch.Solid {
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continue
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}
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switch side {
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case Top:
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c.Top = true
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c.TopPoint = point
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c.TopPixel = swatch
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case Bottom:
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c.Bottom = true
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c.BottomPoint = point
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c.BottomPixel = swatch
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case Left:
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c.Left = true
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c.LeftPoint = point
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c.LeftPixel = swatch
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case Right:
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c.Right = true
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c.RightPoint = point
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c.RightPixel = swatch
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}
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}
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}
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}
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