Fixed collision detection in probes

This was a problem before when the probe hit an object that was further than
another object first. Now we traverse all objects all the time to find the
closest one. \o/

robot.go

@@ -165,17 +165,28 @@ type Instruction struct {
 	Scan        *bool       `json:"scan,omitempty"`
 }
 
-func (r *Robot) checkCollisions(g *game, move_vector v.Vector2d) (bool, v.Point2d, *Robot) {
+// returns collision, the intersection point, and the robot with whom r has
+// collided, if this happened.
+func (r *Robot) checkCollisions(g *game, probe v.Vector2d) (bool, *v.Point2d, *Robot) {
+	finalCollision := false
 	collision := false
-	intersection_point := v.Point2d{X: 0, Y: 0}
-	bot_size := float32(5.0)
-	bot_polygon := v.OrientedSquare(r.Position, r.Heading, bot_size)
+	closest := float32(math.Inf(1))
+	var intersection *v.Point2d
+	var finalRobot *Robot
+
+	// TODO: this needs moved to the conf?
+	botSize := float32(5.0)
+	botPolygon := v.OrientedSquare(r.Position, r.Heading, botSize)
 
 	// Check Walls
-	r_walls := v.AABB2d{A: v.Point2d{X: bot_size, Y: bot_size}, B: v.Point2d{X: g.width - bot_size, Y: g.height - bot_size}}
-	collision, _, pos := v.RectIntersection(r_walls, r.Position, move_vector)
-	if collision {
-		return collision, pos, nil
+	r_walls := v.AABB2d{A: v.Point2d{X: botSize, Y: botSize}, B: v.Point2d{X: g.width - botSize, Y: g.height - botSize}}
+	collision, _, wallIntersect := v.RectIntersection(r_walls, r.Position, probe)
+	if collision && wallIntersect != nil {
+		finalCollision = collision
+		if dist := r.Position.Sub(*wallIntersect).Mag(); dist < closest {
+			intersection = wallIntersect
+			closest = dist
+		}
 	}
 
 	// Check Other Bots
@@ -184,29 +195,47 @@ func (r *Robot) checkCollisions(g *game, move_vector v.Vector2d) (bool, v.Point2
 			if bot.Id == r.Id {
 				continue
 			}
-			player_rect := v.OrientedSquare(bot.Position, bot.Heading, bot_size)
+			player_rect := v.OrientedSquare(bot.Position, bot.Heading, botSize)
 			collision, move_collision, translation := v.PolyPolyIntersection(
-				bot_polygon, move_vector, player_rect)
+				botPolygon, probe, player_rect)
 			if collision || move_collision {
-				return true, r.Position.Add(move_vector).Add(translation.Scale(1.1)), bot
+				finalCollision = collision
+				p := r.Position.Add(probe).Add(translation.Scale(1.2))
+				if dist := r.Position.Sub(p).Mag(); dist < closest {
+					intersection = &p
+					closest = dist
+					finalRobot = bot
+				}
+			}
+		}
+	}
+	// Check Obstacles
+	for _, obj := range g.obstacles {
+		// collision due to motion:
+		collision, move_collision, translation := v.PolyPolyIntersection(
+			botPolygon, probe, obj.Bounds.ToPolygon())
+
+		if collision || move_collision {
+			finalCollision = collision
+			p := r.Position.Add(probe).Add(translation.Scale(1.1))
+			if dist := r.Position.Sub(p).Mag(); dist < closest {
+				intersection = &p
+				closest = dist
+			}
+		}
+
+		// collision due to probe
+		collision, _, wallIntersect := v.RectIntersection(obj.Bounds, r.Position, probe)
+		if collision && wallIntersect != nil {
+			finalCollision = collision
+			if dist := r.Position.Sub(*wallIntersect).Mag(); dist < closest {
+				intersection = wallIntersect
+				closest = dist
 			}
 		}
 	}
 
-	// Check Obstacles
-	for _, obj := range g.obstacles {
-		collision, move_collision, translation := v.PolyPolyIntersection(
-			bot_polygon, move_vector, obj.Bounds.ToPolygon())
-
-		if collision || move_collision {
-			// log.Printf(" COLLISION: %v %v %v\n", collision, move_collition, translation)
-			// log.Printf(" DETAILS: %v %v\n", r.Position, move_vector)
-			// log.Printf(" INPUT: %v %v %v\n", bot_polygon, obj.Bounds.ToPolygon(), obj.Bounds)
-			return true, r.Position.Add(move_vector).Add(translation.Scale(1.1)), nil
-		}
-	}
-
-	return collision, intersection_point, nil
+	return finalCollision, intersection, finalRobot
 }
 
 func (r *Robot) Tick(g *game) {
@@ -287,8 +316,8 @@ func (r *Robot) Tick(g *game) {
 				}
 			}
 
-			if r.Position != intersection_point {
-				r.Position = intersection_point
+			if r.Position != *intersection_point {
+				r.Position = *intersection_point
 			}
 
 			r.Health -= dmg
@@ -343,7 +372,7 @@ func (r *Robot) Tick(g *game) {
 		probe_vector := r.Probe.Sub(r.Position)
 		coll, pos, _ := r.checkCollisions(g, probe_vector)
 		if coll {
-			r.ProbeResult = &pos
+			r.ProbeResult = pos
 		}
 	}
 }