Compare coordonate

Reply to Compare coordonate on Thu, 15 Jul 2010 16:28:52 GMT

bloodhulk — Thu, 15 Jul 2010 16:28:52 GMT

Hi guys

I often read the posts, but i'm unable to find some doc on how compare gem objects coodonates.
It is for a little game project; shooting aliens projected on a surface with balls you throw on it. I need to know how compare aliens coordonate with balls coordonates.

Thx

Nico

Reply to Compare coordonate on Fri, 16 Jul 2010 16:51:34 GMT

bitsynthesis — Fri, 16 Jul 2010 16:51:34 GMT

I suppose it depends on what method you're using to control the position of different gem elements. If you're shifting them around using [translateXYZ] or something like that then this data should be available outside of the gem chain - from whatever you're using to feed [translateXYZ].

Reply to Compare coordonate on Tue, 20 Jul 2010 22:42:40 GMT

bloodhulk — Tue, 20 Jul 2010 22:42:40 GMT

Thanks for your quick answer.
I use [translateXYZ] but i don't know how to make something that compare the data.
I need to bang when the ball coordonate and the video coordonate are similar.

Reply to Compare coordonate on Thu, 22 Jul 2010 20:48:48 GMT

grg — Thu, 22 Jul 2010 20:48:48 GMT

assuming a square/cubic 'bounding box':
Each step of your simulation, substract x-alien from x-ball, [abs], check if smaller than (1/2 size alien + 1/2 size ball). Do the same for y (and z). All 3 true -> collision.

for circles/balls you essentially do the same but use pythagoras to get the center-center distance (make a drawing on paper in 2D and it should be clear).

note that this 'step based' collision detection has drawbacks, if your balls are too fast they can fly through the aliens. It gets tricky then, check if you need it first. Then google collision detection game physics etc.