Jump to content
  • Advertisement
Sign in to follow this  
too_many_stars

Spacial partition help please

This topic is 1140 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi Guys,

 

I read up on spatial partition, created a grid structure with std::vector<Cell> cells where each cell size is 100 x 100 (dealing with 2D here) and at each update, i check when an entity has switched cells. I think so far so good.

 

The problem I believe lies below:

void updateGrid(Grid *grid, std::vector<MovingEntity*> entities,std::vector<Manifold> &manifolds){
	
	for(int y=0;y<grid->num_y_cells;y++){
		for(int x=0;x<grid->num_x_cells;x++){
			
			for(int _y=y-1;_y<=y+1;_y++){
				for(int _x=x-1;_x<=x+1;_x++){
					if(_x<0 || _y<0 || _x>=grid->num_x_cells || _y>=grid->num_y_cells)
						continue;

					for(int out=0;out<grid->cells[_y].entities.size();out++){
						for(int in=0;in<grid->cells[_x].entities.size();in++){
							
							MovingEntity *e1=grid->cells[_y].entities[out];
							MovingEntity *e2=grid->cells[_x].entities[in];

							if(e1==e2)continue;

							e1->aabb.init(e1->pos,e1->half_extents);
							e2->aabb.init(e2->pos,e2->half_extents);
							Contact contact;
							if(myAABBvsAABB(e1->aabb,e2->aabb,contact)){
								
								manifolds.push_back(Manifold(e1,e2,contact));
							}
						}
					}
				}
			}
		}
	}
}

I iteratate over a 1D vector (using the 2d trick) check all neighbouring cells for collision, and attempt to create a contact if one exists.

 

My algo above unfortunatelly is not doing anything. No collisions are detected, even when I fill the screen with AABBs.

 

Could someone tell me please where the error is?

 

Thanks,

 

Mike

Share this post


Link to post
Share on other sites
Advertisement
I don't understand your trick so the moving entities make no sense to me.
&nbsp;
A simple way to debug this is to have one entity, hack some code to detect it should cross the border (based on eg coordinate of it, and very preferably NOT on border detection code you already have), and have a break point in the debugger, or dump the entire grid, or whatever you like to use for debugging.
&nbsp;
Then you can see the situation at that point in time, and figure out what is not what it should be.
&nbsp;
Alternatively, you can run additional check code that all entities are really in the grid they should be, as part of the game loop.
When that check fails, do the above, or fail the program, or whatever.
&nbsp;
Edit: http://www.gamedev.net/page/resources/_/technical/general-programming/debugging-follow-the-data-r3913 may be useful for understanding how to debug Edited by Alberth

Share this post


Link to post
Share on other sites
On both entities, they either use obly x OR y coord, so you gather always the same edges of the grid, but never its interior.

Seems you forgot to combine indices like cellIndex = x + y * grid->num_x_cells ?

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!