Hey... I have a 3d world which i have loaded into my opengl program. All the objects in my scene are imported from .OBJ files. At this stage now im starting to think about collision detection. If I could start to get some basic collision detection up and running i'd be very happy. I think i understand the basics of how collision detection works, or this for of it anyway. Every object in my world must have a bounding box, and tests must be carried out every frame to see of any of these boxes have intersected...right? No i'm just having some trouble thinking of how to implement this. When I read in an object from an .OBJ file, should i create an invisible box around it then? If i do this i can see one problem in my situation. The folowing image shows my scene...this is loading in in one single OBJ file...so any box which bounded the whole thing would be useless?? would it be better to load in seperate models for the wall, road, sidewalk e.t.c? Any help anyone could provide would be great! I look forward ot reading some replies thanks

Hallo,

Just so you know, I don't have much experience when it comes to collision detection, so if someone tells you I'm wrong, ignore anything I said.

I dont think you need to have a bounding box, but it makes things a lot faster. As the case is in the program I'm writing I first check if there is a collision between the bounding box of the object. If there is, I do more checks to see which of the triangles of the object it hits. This is just to speed things up, as it is easier to do one check against the bounding box, than to do one check for each of the triangles for each timestep. In fact, most games only do bounding box checking I think (or have multiple bounding boxes covering their objects)

Also, you want to do the collision detection more the ones a frame, to ensure that you get a good result.

I think there is a openGL tutorial covering this (NeSh or something), but from what I remember the code is a bit messy.

Best of luck

hey,

You should check out the great tutorial written by Paul Nettle (http://www.gamedev.net/reference/articles/article1026.asp) on collision detection. It should provide you with all thats required to perform simple collision detection against you scene...

Hope this is helpful

Quote:Original post by oliii
Paul Nettle's stuff is good, but I'm not 100% sure it's actually right.

If I remember correctly there were some issues for edge collisions, can't quite remember if it was because he didn't covered them, the algorithm just pushed the sphere back all the way out of the triangle plane or both.

Also, avoid ellipsoids and you will avoid a headache. [smile]

thanks guys...i'm just making my way through reading lots of stuff on it now..lost of work lol!