Assignment 4 : Go-Kart Collision
Assignment Description
In this assignment., we create a simple game where a Go-Kart with 1 or more polygons is set into motion and use it to detect collisions with other objects or mesh in the scene. Because my earlier scene is a basketball court with only a few lamp posts to do collision, I decide to make another scene in 3D studio max and load it into my scene. I modelled a maze containing some spheres which are to be collected in the simple game by running the Go-Kart into spheres after finding them in the maze.
Game Description
This is a simple game where you drive a Armoured Personal Carrier around a maze to collect SWAT members that are lost in the game. You will complete the game when u find the 5 SWAT team members. As there was insufficient time, I was unable to do an elapsed timer to check for how long you take to complete the game.
Game Controls
Up/w : Accelerate
Down/s : Decelerate
Left/a : Turn Vehicle Left
Right/d : Turn Vehicle Right
b : Toggle Bounding Box Display
Collision Detection Method
I used Oriented Bounding Box(OBB) test against other Oriented Bounding Box. I used the Separating Axis Theorem to detect the overlapping of OBBs. Oriented Bounding Box is able to bound the mesh tighter than a Axis Aligned Bounding Box (AABB) and thus I choose this method of detection.
For OBBs, the separating axis test must be generalized to three dimensions. A box's scalar projection onto a unit vector L creates an interval along the axis defined by L.
The radius of the projection of box A onto L is
The same is true for B, and L forms a separating axis if
Note that L does not have to be a unit vector for this test to work. The boxes A and B are disjoint if none of the 6 principal axes and their 9 cross products form a separating axis. These tests are greatly simplified if T and B’s basis vectors (B1, B2, B3) are transformed into A’s coordinate frame.
However to increase efficiency, I did a Sphere Sphere collision test first before I do a OBB intersection test because OBB intersection test is computationally much more expensive than a Sphere to Sphere Collision test. I check the Go-Kart against all objects in the scene. As there was insufficient time, I was unable to implement a quad-tree to divide the scene up further to make the collision checks more efficient.
Collision Response
The collision response I did in this simple game is that when you hit a wall, you will bounce back in the opposite direction of that you were traveling. In order to more simulation physics, I did a damping effect on the speed such that you will only bounce back at 75% of the speed you are traveling at and also include a friction component so that you need to keep pressing the accelerate key if you want the vehicle to continue to move forward as left alone the vehicle will slow to a stop.
Screenshots
Starting Screen, Vroommming!!
With Bounding Boxes Activated
Yeah going to collect one of the SWAT team member
YEAH Win!!!!!
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