Hi all,

I'm struggling to understand a way to implement a simple scoring system based of where the collision occurred. I currently have a ball (mesh sphere) hitting a target (sprite) using AABBs. The problems I'm trying to solve are:

1) How to avoid raising a collision for transparent sprites (i.e. my target is 256x256 and a majority of it is transparent)
2) How to detect where the ball hit the target and update the score accordingly (e.g. bullseye is worth more than outer edge)

I thought I could solve both these problems by creating a hit map which is basically color coded to indicated score (bullseye is red, outer edge is blue) that I would check during a collision. I thought I could use this same procedure to check the alpha to see if I had a legitimate collision.

I created a staging texture to hold my hit map but I don't think there is any way to transform the world-space coordinates of the collision into something useful that I can use to figure out what pixel in my hit map was hit.

Was I on the right track and is there a way to figure out the right coordinates in my hit map, or is there another way of doing this?

Thanks,

Ping Can anyone help me with this? Is there a better way of doing it?

OK so my plan was to grab the x,y,z in projection space of where ball is when a AABB collision is detected. What i'm stuck on is how do I get those coordinates into something useful.

If I unproject into the targets model space will that give me something I can then try to use? I tried it and it seems to give me garbage. Are there any articles on this? I found this thread http://groups.google.com/group/cocos2d-iphone-discuss/browse_thread/thread/f6e734e00d863f5e/41768952a1bcca0e?lnk=gst&q=image+mask&pli=1 which is basically what I want to do but i'm not sure why he is able to use the coordinates without performing any transformations.

Thanks,