src/net/habraun/kong/physics/SimpleNarrowPhase.scala

   1 /*
   2         Copyright (c) 2009 Hanno Braun <hanno@habraun.net>
   3
   4         Licensed under the Apache License, Version 2.0 (the "License");
   5         you may not use this file except in compliance with the License.
   6         You may obtain a copy of the License at
   7
   8                 http://www.apache.org/licenses/LICENSE-2.0
   9
  10         Unless required by applicable law or agreed to in writing, software
  11         distributed under the License is distributed on an "AS IS" BASIS,
  12         WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13         See the License for the specific language governing permissions and
  14         limitations under the License.
  15 */
  16
  17
  18
  19 package net.habraun.kong.physics
  20
  21
  22
  23 class SimpleNarrowPhase extends NarrowPhase {
  24
  25         def inspectCollision(b1: Body, b2: Body) = {
  26                 if (b1.shape.isInstanceOf[Circle] && b2.shape.isInstanceOf[Circle]) {
  27                         val circle1 = b1.shape.asInstanceOf[Circle]
  28                         val circle2 = b2.shape.asInstanceOf[Circle]
  29                         val dSquared = (b1.position - b2.position).squaredLength
  30                         if (dSquared <= circle1.radius + circle2.radius) {
  31                                 val normal1 = (b2.position - b1.position).normalize
  32                                 val normal2 = (b1.position - b2.position).normalize
  33                                 Some(Collision(b1, b2, normal1, normal2, Vec2D(0, 0)))
  34                         }
  35                         else {
  36                                 None
  37                         }
  38                 }
  39                 else if (b1.shape.isInstanceOf[Circle] && b2.shape.isInstanceOf[LineSegment]) {
  40                         circleLineSegment(b1, b2, b1.shape.asInstanceOf[Circle], b2.shape.asInstanceOf[LineSegment])
  41                 }
  42                 else if (b1.shape.isInstanceOf[LineSegment] && b2.shape.isInstanceOf[Circle]) {
  43                         val collision = circleLineSegment(b2, b1, b2.shape.asInstanceOf[Circle],
  44                                         b1.shape.asInstanceOf[LineSegment]).getOrElse { throw new AssertionError }
  45                         Some(Collision(b1, b2, collision.normal2, collision.normal1, Vec2D(0, 0)))
  46                 }
  47                 else {
  48                         None
  49                 }
  50         }
  51
  52
  53
  54         private[this] def circleLineSegment(b1: Body, b2: Body, circle: Circle, lineSegment: LineSegment):
  55                         Option[Collision] = {
  56                 val circle = b1.shape.asInstanceOf[Circle]
  57                 val lineSegment = b2.shape.asInstanceOf[LineSegment]
  58
  59                 val p = b2.position + lineSegment.p1
  60                 val d = (lineSegment.p2 - lineSegment.p1).normalize
  61                 val tmax = (lineSegment.p2 - lineSegment.p1).length
  62
  63                 val m = p - b1.position
  64                 val b = m * d
  65                 val c = (m * m) - circle.radius * circle.radius
  66                 val dis = b * b - c
  67                 if (dis >= 0) {
  68                         val t1 = -b + Math.sqrt(dis)
  69                         val t2 = -b - Math.sqrt(dis)
  70                         if (t2 >= 0 && t1 <= tmax) {
  71                                 val cp = b1.position
  72                                 val v = lineSegment.p2 - lineSegment.p1
  73                                 val t = -(((p.x - cp.x) * v.x) + ((p.y - cp.y) * v.y)) / ((d.x * v.x) + (d.y * v.y))
  74                                 val normal1 = (p + (d * t)).normalize
  75                                 val normal2 = normal1.inverse
  76                                         Some(Collision(b1, b2, normal1, normal2, Vec2D(0, 0)))
  77                         }
  78                         else {
  79                                 None
  80                         }
  81                 }
  82                 else {
  83                         None
  84                 }
  85         }
  86 }