Am I going to regret using a color based collision detection system?

Question

I'm just getting started build my first game with XNA (I'm experienced with C# but not games).

I'm building a pretty simple top down 2d shooter. I read this tutorial on using a color based collision system and it sounded really cool to me. http://www.xnadevelopment.com/tutorials/theroadnottaken/theroadnottaken.shtml

It means I can quickly make levels just using any graphics program and not have to define my scenery (walls, trees etc) in terms of collision boxes etc right?

However I can see that going down this path means that perhaps the calculation for determining whether fast moving objects like bullets intersect walls etc becomes more difficult potentially because you cant' do basic geometry intersection type calcs.

Is that right? Am I going to regret going in this direction if my game gets more complex over time? Worth just investing in the creation of a level editor to define my scenery in terms of geometry?

Any advice for a noob very much appreciated!

Answer 1

You're spot on with your observations regarding the capabilities of a bitmap based collision approach.

This method provides a really easy way to edit your levels with any program that can output a bitmap (any image editing program). This system is also really flexible when you want to define different types of ground. Say green for mud, and red for a solid underground. You then easily query the current pixel and determine the type of underground the player stands on. Even ramps (gradients from ground type A to B) are possible without much problems.

Problems arise with collision detection. It's easy to detect an intersection with another object (just do a pixel-test), but it's hard (computationally expensive) to find out what orientation the object you collided with has. This is especially important when you need a surface normal to deflect objects correctly.

Also really fast moving objects can be an issue, especially if you have thin (eg. 1 pixel wide) objects to collide with. There's this question that covers this topic already.

In the end it all depends on what kind of game you want to create and what resolution (in terms of collision detection/resolving) you need. The bitmap based approach works best, when a large portion of your world is static. But it also allows you to implement stuff like destructible levels quite easily.

Since you didn't mention the type of game you want to create, it's now up to you to decide whether or not a bitmap-based collision approach would be beneficial for your game. Good luck.