Refactored use of SAT collision checking.

collider_visualizer/worldColliderDisplay.go

@@ -4,6 +4,7 @@ import (
 	. "dnmshared"
 	"fmt"
 	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/kvartborg/vector"
 	"github.com/solarlune/resolv"
 	"go.uber.org/zap"
 	"image/color"
@@ -56,7 +57,7 @@ func NewWorldColliderDisplay(game *Game, stageDiscreteW, stageDiscreteH, stageTi
     if moveToCollide {
         toTestPlayerCollider := playerColliders[0] 
         oldDx := 0.0
-        oldDy := 180.0
+        oldDy := 135.0
         dx := oldDx
         dy := oldDy
         if collision := toTestPlayerCollider.Check(oldDx, oldDy, "Barrier"); collision != nil {
@@ -64,11 +65,26 @@ func NewWorldColliderDisplay(game *Game, stageDiscreteW, stageDiscreteH, stageTi
             barrierShape := collision.Objects[0].Shape.(*resolv.ConvexPolygon)
             origX, origY := playerShape.Position() 
             playerShape.SetPosition(origX+oldDx, origY+oldDy)
-            if mtv := CalculateMTVForConvexPolygon(playerShape, barrierShape); mtv != nil {
+            if colliding := IsPolygonPairColliding(playerShape, barrierShape, nil); colliding {
-                Logger.Info(fmt.Sprintf("Collided: shape=%v, oldDx=%v, oldDy=%v, MTV=%v", toTestPlayerCollider.Shape, oldDx, oldDy, mtv))
+                Logger.Info(fmt.Sprintf("Collided: playerShape=%v, oldDx=%v, oldDy=%v", playerShape, oldDx, oldDy))
-                //dx, dy = mtv[0], mtv[1]
+                overlapResult := &SatResult{
+                    Overlap: 0,
+                    OverlapX: 0, 
+                    OverlapY: 0, 
+                    AContainedInB: true,
+                    BContainedInA: true,
+                    Axis: vector.Vector{0, 0},
+                }
+                e := vector.Vector{oldDx, oldDy}.Unit()
+                if separatableAlongMovement := IsPolygonPairSeparatedByDir(playerShape, barrierShape, e, overlapResult); !separatableAlongMovement {
+                    pushbackX, pushbackY := overlapResult.Overlap*overlapResult.OverlapX, overlapResult.Overlap*overlapResult.OverlapY  
+                    Logger.Info(fmt.Sprintf("Collided: playerShape=%v, oldDx=%v, oldDy=%v, toCheckBarrier=%v, pushbackX=%v, pushbackY=%v", playerShape, oldDx, oldDy, barrierShape, pushbackX, pushbackY))
+                    dx, dy = oldDx-pushbackX, oldDy-pushbackY 
                 } else {
-                Logger.Info(fmt.Sprintf("Collided: shape=%v, oldDx=%v, oldDy=%v, toCheckBarrier=%v, not intersecting", toTestPlayerCollider.Shape, oldDx, oldDy, barrierShape))
+                    Logger.Info(fmt.Sprintf("Not Collided: playerShape=%v, oldDx=%v, oldDy=%v, toCheckBarrier=%v, e=%v", playerShape, oldDx, oldDy, barrierShape, e))
+                }
+            } else {
+                Logger.Info(fmt.Sprintf("Not collided: playerShape=%v, oldDx=%v, oldDy=%v, toCheckBarrier=%v", playerShape, oldDx, oldDy, barrierShape))
             }  
 
             playerShape.SetPosition(origX, origY)

dnmshared/geometry.go

@@ -15,6 +15,10 @@ type Vec2D struct {
 	Y float64 `json:"y,omitempty"`
 }
 
+func NormVec2D(dx, dy float64) Vec2D {
+    return Vec2D{dy, -dx}
+}
+
 type Polygon2D struct {
 	Anchor *Vec2D   `json:"-"` // This "Polygon2D.Anchor" is used to be assigned to "B2BodyDef.Position", which in turn is used as the position of the FIRST POINT of the polygon.
 	Points []*Vec2D `json:"-"`

dnmshared/resolv_helper.go

@@ -43,40 +43,129 @@ func GenerateConvexPolygonCollider(unalignedSrc *Polygon2D, spaceOffsetX, spaceO
 	return collider
 }
 
-func CalculateMTVForConvexPolygon(cp *resolv.ConvexPolygon, other *resolv.ConvexPolygon) vector.Vector {
+type SatResult struct {
-	delta := vector.Vector{0, 0}
+	Overlap  float64
-
+	OverlapX float64
-	smallest := vector.Vector{math.MaxFloat64, 0}
+	OverlapY float64
-
+	AContainedInB     bool
-    for _, axis := range cp.SATAxes() {
+	BContainedInA     bool
-        if !cp.Project(axis).Overlapping(other.Project(axis)) {
+    Axis vector.Vector
-            return nil
 }
 
-        overlap := cp.Project(axis).Overlap(other.Project(axis))
+func IsPolygonPairColliding(a, b *resolv.ConvexPolygon, result *SatResult) bool {
-
+	aCnt, bCnt := len(a.Points), len(b.Points)
-        if smallest.Magnitude() > overlap {
+	// Single point case
-            smallest = axis.Scale(overlap)
+	if 1 == aCnt && 1 == bCnt {
+		if nil != result {
+			result.Overlap = 0
+		}
+		return a.Points[0].X() == b.Points[0].X() && a.Points[0].Y() == b.Points[0].Y()
 	}
 
+	if 1 < aCnt {
+		for _, axis := range a.SATAxes() {
+			if IsPolygonPairSeparatedByDir(a, b, axis.Unit(), result) {
+				return false
+			}
+		}
 	}
 
-    for _, axis := range other.SATAxes() {
+	if 1 < bCnt {
-
+		for _, axis := range b.SATAxes() {
-        if !cp.Project(axis).Overlapping(other.Project(axis)) {
+			if IsPolygonPairSeparatedByDir(a, b, axis.Unit(), result) {
-            return nil
+				return false
+			}
+		}
 	}
 
-        overlap := cp.Project(axis).Overlap(other.Project(axis))
+	return true
-
-        if smallest.Magnitude() > overlap {
-            smallest = axis.Scale(overlap)
 }
 
+func IsPolygonPairSeparatedByDir(a, b *resolv.ConvexPolygon, e vector.Vector, result *SatResult) bool {
+	var aStart, aEnd, bStart, bEnd float64 = math.MaxFloat64, -math.MaxFloat64, math.MaxFloat64, -math.MaxFloat64
+	for _, p := range a.Points {
+		dot := p.X()*e.X() + p.Y()*e.Y()
+
+		if aStart > dot {
+			aStart = dot
 		}
 
-	delta[0] = smallest[0]
+		if aEnd < dot {
-	delta[1] = smallest[1]
+			aEnd = dot
-
+		}
-	return delta
+	}
+
+	for _, p := range b.Points {
+		dot := p.X()*e.X() + p.Y()*e.Y()
+
+		if bStart > dot {
+			bStart = dot
+		}
+
+		if bEnd < dot {
+			bEnd = dot
+		}
+	}
+
+	if aStart > bEnd || aEnd < bStart {
+		// Separated by unit vector "e"
+		return true
+	}
+
+	if nil != result {
+        result.Axis = e
+		overlap := float64(0)
+
+		if aStart < bStart {
+			result.AContainedInB = false
+
+			if aEnd < bEnd {
+				overlap = aEnd - bStart
+				result.BContainedInA = false
+			} else {
+				option1 := aEnd - bStart
+				option2 := bEnd - aStart
+				if option1 < option2 {
+					overlap = option1
+				} else {
+					overlap = -option2
+				}
+			}
+		} else {
+			result.BContainedInA = false
+
+			if aEnd > bEnd {
+				overlap = aStart - bEnd
+				result.AContainedInB = false
+			} else {
+				option1 := aEnd - bStart
+				option2 := bEnd - aStart
+				if option1 < option2 {
+					overlap = option1
+				} else {
+					overlap = -option2
+				}
+			}
+		}
+
+		currentOverlap := result.Overlap
+		absoluteOverlap := overlap
+		if overlap < 0 {
+			absoluteOverlap = -overlap
+		}
+
+		if 0 == currentOverlap || currentOverlap > absoluteOverlap {
+			var sign float64 = 1
+			if overlap < 0 {
+				sign = -1
+			}
+
+			result.Overlap = absoluteOverlap
+			result.OverlapX = e.X() * sign
+			result.OverlapY = e.Y() * sign
+		}
+	}
+
+	// the specified unit vector "e" doesn't separate "a" and "b", overlap result is generated
+	return false
 }