change of bounds computation

engine/actor.go

@@ -19,16 +19,21 @@ func init() {
 // Actor handles basic movement.
 type Actor struct {
 	CollisionDomain string    // id of component to look for colliders inside of
-	Pos, Size       geom.Int3 // in voxels; multiply by game.VoxelScale for regular Euclidean space
+	Pos             geom.Int3 // in voxels; multiply by game.VoxelScale for regular Euclidean space
+	Bounds          geom.Box  // in voxels; relative to Pos
 
 	rem  geom.Float3
 	game *Game
 }
 
+func (a *Actor) BoundingBox() geom.Box {
+	return a.Bounds.Add(a.Pos)
+}
+
 // CollidesAt runs a collision test of the actor, supposing the actor is at a
 // given position (not necessarily a.Pos).
 func (a *Actor) CollidesAt(p geom.Int3) bool {
-	bounds := geom.Box{Min: p, Max: p.Add(a.Size)}
+	bounds := a.Bounds.Add(p)
 	for c := range a.game.Query(a.CollisionDomain, ColliderType) {
 		if c.(Collider).CollidesWith(bounds) {
 			return true

engine/prisms.go

@@ -35,14 +35,13 @@ type PrismMap struct {
 	ID
 	Disabled
 	Hidden
-	Ersatz        bool
-	Map           map[geom.Int3]*Prism // pos -> prism
-	DrawOrderBias image.Point          // dot with pos.XY() = bias value
-	DrawOffset    image.Point          // offset applies to whole map
-	PosToWorld    geom.IntMatrix3x4    // p.pos -> world voxelspace
-	PrismSize     geom.Int3            // in world voxelspace units
-	PrismTop      []image.Point        // polygon vertices anticlockwise, Y means Z
-	Sheet         Sheet
+	Ersatz     bool
+	Map        map[geom.Int3]*Prism // pos -> prism
+	DrawOffset image.Point          // offset applies to whole map
+	PosToWorld geom.IntMatrix3x4    // p.pos -> world voxelspace
+	PrismSize  geom.Int3            // in world voxelspace units
+	PrismTop   []image.Point        // polygon vertices anticlockwise, Y means Z
+	Sheet      Sheet
 
 	game      *Game
 	pwinverse geom.RatMatrix3
@@ -152,7 +151,7 @@ func (p *Prism) Draw(screen *ebiten.Image, opts *ebiten.DrawImageOptions) {
 
 func (p *Prism) DrawOrder() (int, int) {
 	return p.m.PosToWorld.Apply(p.pos).Z,
-		geom.Dot(p.pos.XY(), p.m.DrawOrderBias)
+		geom.Dot(p.pos.XY(), image.Point(p.m.game.Projection).Mul(-1))
 }
 
 func (p *Prism) Transform() (opts ebiten.DrawImageOptions) {

game/aw.go

@@ -72,9 +72,7 @@ func (aw *Awakeman) Update() error {
 	if ebiten.IsKeyPressed(ebiten.KeyShift) {
 		z = 2.0
 	}
-	pos := aw.Sprite.Actor.Pos
-	size := aw.Sprite.Actor.Size
-	aw.camera.PointAt(pos.Add(size.Div(2)), z)
+	aw.camera.PointAt(aw.Sprite.Actor.BoundingBox().Centre(), z)
 	return nil
 }
 

game/level1.go

@@ -30,8 +30,8 @@ func Level1() *engine.Scene {
 				Factor: 0.5,
 			},
 			&engine.PrismMap{
-				ID:            "hexagons",
-				DrawOrderBias: image.Pt(0, -1), // draw higher Y after lower Y
+				ID: "hexagons",
+				//DrawOrderBias: image.Pt(0, -1), // draw higher Y after lower Y
 				PosToWorld: geom.IntMatrix3x4{
 					// For each tile in the X direction, go right by 24 and
 					// forward by 8, etc
@@ -264,9 +264,12 @@ func Level1() *engine.Scene {
 					Actor: engine.Actor{
 						CollisionDomain: "level_1",
 						Pos:             geom.Pt3(100, -64, 100),
-						Size:            geom.Pt3(8, 16, 2),
+						Bounds: geom.Box{
+							Min: geom.Pt3(-4, -16, -1),
+							Max: geom.Pt3(4, 0, 1),
+						},
 					},
-					DrawOffset: image.Pt(-1, 0),
+					DrawOffset: image.Pt(-5, -16),
 					Sheet: engine.Sheet{
 						AnimDefs: map[string]*engine.AnimDef{
 							"idle_left": {Steps: []engine.AnimStep{

geom/box.go

@@ -36,6 +36,11 @@ func (b Box) Size() Int3 {
 	return b.Max.Sub(b.Min)
 }
 
+// Centre returns the centre point of the box.
+func (b Box) Centre() Int3 {
+	return b.Min.Add(b.Max).Div(2)
+}
+
 // Add offsets the box by vector p.
 func (b Box) Add(p Int3) Box {
 	return Box{