Understanding 2D Collision Detection in Game Development

Explore the intricacies of 2D collision detection in game development through methods like distance checks, bounding shapes, and optimizing collision tests. Dive into concepts like sprite speed assumptions, square-square collisions, and rectangle testing complexities. Learn about useful Rectangle methods and their applications in MonoGame.

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• Game Development
• Collision Detection
• 2D Graphics
• Sprite Animation
• MonoGame

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Uploaded on Apr 20, 2024 | 5 Views

Presentation Transcript

1. 2D Collision Detection CSE 3902 BY: MATT BOGGUS

2. Underlying assumption about speed of sprites Live example in class

3. Collision tests Distance check Bounding shapes Pixel based Outline Iterating on collidables Exhaustive comparison Optimizations

4. Collision detection tests

5. Distance check (point vs. sprite)

6. Distance check (point vs. circle)

7. (Axis aligned) Square-square test

8. Square-square test

9. Square-square left-right side collision

10. Square-square top-bottom side collision

11. Rectangle collision?

12. (Axis-aligned) Rectangle testing

13. Rectangle testing On your own, compare to complexity of example on http://jeffreythompson.org/collision-detection/rect-rect.php

14. Useful Rectangle methods Given two Rectangles rectangleA and rectangleB Rectangle.Intersects(Rectangle) Returns true if the rectangles are intersecting, otherwise false Example call: rectangleA.Intersects(rectangleB); Rectangle.Intersect Method (Rectangle, Rectangle) Returns the area where the two rectangles overlap, an empty rectangle if there is no overlap Example call: Rectangle.Intersect(rectangleA,rectangleB); MonoGame Rectangle reference page

15. Rectangle Intersect left-right

16. Rectangle Intersect top-bottom

17. Velocity vectors as another tool for side determination

18. Bounds checking, position vs. environment min and max values

19. Bounds checking, position vs. environment min and max values

20. Or reuse rectangle logic

21. Or reuse rectangle logic

22. Pixel-pixel collision detection As loops: Foreach (x pixel coordinate){ Foreach (y pixel coordinate){ /* Are there multiple sprites with a non- transparent color at (x,y) */ }} As bitwise operations (XOR == 1) Not intersecting (XOR == 0) AND (OR == 1) Intersecting Raster graphic sprites (left) and masks (right)

23. Iterating on collidables

24. Exhaustive comparison: first approach Given gameObjectList(length n), for(int i = 0; i < n; i++) { for(int j = 0; j < n; j++) { // test gameObjectList[i] against gameObjectList[j] } }

25. Exhaustive comparison: avoiding duplicate tests Given gameObjectList(length n), test: gameObjectList[0] vs. gameObjectList[1] through [n-1] gameObjectList[1] vs. gameObjectList[2] through [n-1] gameObjectList[n-2] vs. gameObjectList[n-1]

26. Exhaustive comparison: more considerations Given enemyList (length n), blockList (length m), consider cases: Skip cases when (i == j), enemyList[0] vs. enemyList[1] through [n-1] enemyList[1] vs. enemyList[0] and enemyList[2] through [n-1] enemyList[2] vs. enemyList[0], enemyList[1], and enemyList[3] through [n-1] blockList[0] vs. blockList[1] through [m-1]

27. Optimization: Static and Dynamic Categories Non-moving, or static, objects only need to be compared against dynamics, not other static objects foreach dynamic object, test against all static objects all other dynamic objects, avoiding duplicate tests

28. Optimization: sort and sweep

29. Optimization data structure: quadtrees