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CRE Programming Club Class #9

CRE Programming Club Class #9. Robert Eckstein and Robert Heard. Let’s Look at some Homework. JGT020-6 (Andy Friedrich) BDJ016-0 (Ashley Hartenstein) BXX981 (Arnav Chopra). Video. https://www.youtube.com/watch?v=dU1xS07N-FA. Collision Detection.

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CRE Programming Club Class #9

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  1. CRE Programming Club Class #9 • Robert Eckstein and Robert Heard

  2. Let’s Look at some Homework • JGT020-6 (Andy Friedrich) • BDJ016-0 (Ashley Hartenstein) • BXX981 (Arnav Chopra)

  3. Video • https://www.youtube.com/watch?v=dU1xS07N-FA

  4. Collision Detection • Two objects are said to “collide” if they come in contact with each other. • Collision detection is an essential aspect of nearly all video games. • Algorithms help to detect the collision. For the most part, you can just find someone else’s algorithm and copy it!

  5. Collision Detection • Import LLW706 • Have fun with this “game” for a little bit. • Enter an angle between 0 and 360 (0 is up, angles increase clockwise) and a distance in pixels. See if you can get the turtle to collide with the CRE Logo.

  6. Source Code Hunting • Look through the source code for LLW706. • See if you can find where the code that checks for the collision detection is… • Look for a place where the X and Y position of the turtle is compared to the right, left, top, and bottom position of the graphic.

  7. Line 52! • If Turtle.x > x and Turtle.x < x + 93 • and Turtle.y > y and Turtle.y < y + 96 Then • ‘ There is a collision between logo/turtle! • EndIf

  8. Bounding Boxes • When working with collision detection, it helps to think of shapes or graphics as being surrounded by a “shrinkwrapped rectangle.” This is called a bounding box. Here is a blue bounding box around an early Mario.

  9. Bounding Boxes • Bounding Boxes can also be very complex, and are used in more modern 3D games as well!

  10. Why Use a Bounding Box? • Because it’s quick and easy to compute when things run into each other…. just figure out if the rectangles are touching!

  11. Works With Circles Too • To figure out if something is colliding with a circle, just see if the distance between some point and the center of the circle is less than the radius. • Two circles? Just see if the distance between the centers is less than the two radius values added together. • You’ll need to be familiar with the Pythagoreon Therom.

  12. Are BBs Perfect? • No! But for simple games, it’s generally good enough. • Sub DoBoxesIntersect • box1Left = box1X • box1Top = box1Y • box1Bottom = box1Y + box1Height • box1Right = box1X + box1Width • box2Left = box2X • box2Top = box2Y • box2Bottom = box2Y + box2Height • box2Right = box2X + box2Width

  13. Here’s the Rest of It… • If (box1Bottom < box2Top) Or (box1Top > box2Bottom) Or (box1Left > box2Right) Or (box1Right < box2Left) Then • Shapes.HideShape(intersect) • Else • Shapes.ShowShape(intersect) • EndIf • EndSub

  14. Import QSP227 • Run this program. Use the arrow keys to move one of the rectangles around. • Note that when it collides with the other rectangle, a message appears at the bottom. • USE THIS ALGORITHM IN YOUR OWN PROGRAMS!

  15. Why Does This Work? • Talk To Your Teachers! See if you can figure out why that algorithm works. (HINT: Look at the intersecting rectangle made by the two squares on slide 12.) • It’s much more efficient than checking to see if any of the four corners of one rectangle are inside the boundaries of another rectangle.

  16. Homework • Continue working on your state machine. • This time, when in the PLAY_GAME state, don’t kick it into the third state unless there is a collision of some sort. Add multiple shapes. Be creative! Have fun! • Email me with questions…

  17. Next Time... • No class next week due to STAAR tests. • We’ll get back together the following week and really start cranking out some game code.

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