Re: [Algorithms] Broadphase collision

[John R. <jra...@gm...>]

Priyank,

Unless you want to write your own collision/physics engine yourself 'just
for fun' I strongly recommend you just use one of the many freely available
versions.  It's a large engineering project and almost for sure not worth
your time.

Check out; 'Bullet', 'OpCode', or 'PhysX' to name just a few.  All three of
these are free for commercial or non-commercial use and represent literally
man-years of engineering time invested.

Personally, I get no pleasure from re-writing code that is readily available
from other sources.  Unless you are writing it purely as a learning
exercise, I can't fathom a reason why you would do this.  Presumably you are
trying to create an actual game project, so wouldn't you prefer to be
working on your game instead of solving problems that have been solved many
times before by others and shared with the development community free of
charge?

John

On Wed, Mar 24, 2010 at 1:50 PM, Priyank Jain <fly...@gm...> wrote:

> Hi,
>
> I apologize in advance, but I'm not sure if my earlier message about
> broadphase collision got posted or not. Earlier when I posted it, it
> gave me a bounce-back error, saying that the message was too long, so am
> not sure if my question got posted.
>
> If none of you received it, please let me know.
>
> Thanks
> /Priyank
>
> On 3/24/2010 1:22 PM, Priyank Jain wrote:
> > Hi,
> > I am trying to implement broadphase collision for my game (3D FPS
> > genre). I have been reading about the commonly used techniques and I
> > have tailored the grid approach to my game. I want to know if this is
> > the right direction to go in or not.
> > The involved actors are :-
> > Players
> > Bullets(Fired)
> > Weapons (placed at points located throughout the level, which other
> > players can pick up, aka static objects)
> > World
> > As of now, I am just trying to get the Players and bullet collision
> > pairs.
> > Players: Players are represented by a bounding sphere, located at a
> > position and moving with a velocity. Each player would have
> > approximately the bounding sphere of same size.
> > Players - weapons
> > Players - World
> > Bullets: Bullets are represented by a segment with a start point and
> > an end point (using posn, posn + vel) (each frame). Bullet can hit :-
> > Fired Bullet     Player
> > (Other) Bullet
> > World
> >
> > Approach:
> > - As each player and bullet is created, associate a reference to each
> > entity within CollisionMgr as a list<Player*> and list<Bullet*>.
> > - On each update frame, do the following:
> > - For each player, find Cell(s); it is associated with :=> list< Cell*
> > > PlayerCells
> > - For each Bullet (segment), find Cell(s); it is associated with :=>
> > list< Cell* > BulletCells
> > - For each entity, the cell(s) can be found out based on the entity.
> > - Player: Bounding sphere :The grid size are uniformly sized cell
> > (size, M) such that the M = 2R (R = radius of the bounding sphere).
> > Thus, at any given time, at most the bounding sphere can be in contact
> > with 4 cells. To determine the cells associated, find the 8 points for
> > a given sphere (each at 45 degrees to the X,Y,Z axis along the 8
> > octants). (And then find out, in which grid cell does each of the
> > point lie. This could at max return 4 cells).
> > - Bullet: Segmented Ray with endpoints at : Posn and (Posn + vel).
> > Thus, all the cells that the line passes through would yield the cells.
> > - Cell can be a structure like
> > Cell {
> > List < Player*>
> > List < Bullet* >
> > Value (x,y,z) => unique value based on these three coordinates
> > }
> > - As a cell is found by either of the entities, given its coordinates
> > and grid position, a cell can be put on the hash-map. As the players
> > and bullets yield cells, they can be referenced using this map and
> > in-turn populate the list of player and bullet residing within that
> > cell structure.
> > - After all the player and bullet –affected cells have been found, if
> > we iterate through the hash-map, then it would yield all the possible
> > pair of colliding players and bullets in a given cell. This can then
> > be further handled using narrow-phase collision.
> >
> > Does this sound feasible ? I'd really like to get some feedback on this.
> >
> > Thank you
> > /Priyank Jain
>
>
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