Collision detection with complex shapes

Question

I am wanting to make a game that has each level loaded from an image. I want to draw up the whole level in Photoshop, and then set it as the background and allow the player to walk over it. I want another invisible image to go over top which will be black in all places that I want to collide with.

The reason I don't want to use tiles, which are much easier with rectangle collision and such, is because there will be complex corners and not everything will be rectangle.

Is this a good idea, and is it possible to do easily? Would this be a big CPU hog or is there a better way to do this?

Level image

Obstacles shown in red

Answer 1

..there will be complex corners and not everything will be rectangle.

This could be achieved by drawing and dealing with Shape and Area instances. E.G.

• Yellow is a little animated 'player'.
• The bounds of the image represent walls that contain the path of the player (it bounces off them).
• Obstacles are painted green when not in collision, red otherwise.

import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import java.awt.image.BufferedImage; import javax.swing.*;  class ShapeCollision {      private BufferedImage img;     private Area[] obstacles = new Area[4];     private Area walls;      int x;      int y;     int xDelta = 3;     int yDelta = 2;      /** A method to determine if two instances of Area intersect */     public boolean doAreasCollide(Area area1, Area area2) {         boolean collide = false;          Area collide1 = new Area(area1);         collide1.subtract(area2);         if (!collide1.equals(area1)) {             collide = true;         }          Area collide2 = new Area(area2);         collide2.subtract(area1);         if (!collide2.equals(area2)) {             collide = true;         }          return collide;     }      ShapeCollision() {         int w = 400;         int h = 200;         img = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);         final JLabel imageLabel = new JLabel(new ImageIcon(img));         x = w/2;         y = h/2;          //circle          obstacles[0] = new Area(new Ellipse2D.Double(40, 40, 30, 30));          int[] xTriangle = {330,360,345};         int[] yTriangle = {60,60,40};         //triangle          obstacles[1] = new Area(new Polygon(xTriangle, yTriangle, 3));          int[] xDiamond = {60,80,60,40};         int[] yDiamond = {120,140,160,140};         //diamond          obstacles[2] = new Area(new Polygon(xDiamond, yDiamond, 4));          int[] xOther = {360,340,360,340};         int[] yOther = {130,110,170,150};         // other          obstacles[3] = new Area(new Polygon(xOther, yOther, 4));          walls = new Area(new Rectangle(0,0,w,h));          ActionListener animate = new ActionListener() {              @Override             public void actionPerformed(ActionEvent e) {                 animate();                 imageLabel.repaint();             }         };         Timer timer = new Timer(50, animate);          timer.start();         JOptionPane.showMessageDialog(null, imageLabel);         timer.stop();     }      public void animate() {         Graphics2D g = img.createGraphics();         g.setRenderingHint(                 RenderingHints.KEY_ANTIALIASING,                  RenderingHints.VALUE_ANTIALIAS_ON);          g.setColor(Color.BLUE);         g.fillRect(0, 0, img.getWidth(), img.getHeight());         x+=xDelta;         y+=yDelta;         int s = 15;         Area player = new Area(new Ellipse2D.Double(x, y, s, s));          // Acid test of edge collision;         if (doAreasCollide(player,walls)) {             if ( x+s>img.getWidth() || x<0 ) {                 xDelta *= -1;             }              if(y+s>img.getHeight() || y<0 ) {                 yDelta *= -1;             }         }         g.setColor(Color.ORANGE);         for (Area obstacle : obstacles) {             if (doAreasCollide(obstacle, player)) {                 g.setColor(Color.RED);             } else {                 g.setColor(Color.GREEN);             }             g.fill(obstacle);         }          g.setColor(Color.YELLOW);         g.fill(player);           g.dispose();     }      public static void main(String[] args) {         Runnable r = new Runnable() {              @Override             public void run() {                 new ShapeCollision();             }         };         // Swing GUIs should be created and updated on the EDT         // http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html         SwingUtilities.invokeLater(r);     } } 

Edit

make it detect all the red color and set that as the collision bounds

At start-up, use the source seen in the Smoothing a jagged path question to get an outline of the red pixels (see the getOutline(Color target, BufferedImage bi) method). Store that Area as the single obstacle on start-up.