Collisions That Don't Stop or Slide

Blitz3D Forums/Blitz3D Programming/Collisions That Don't Stop or Slide

HappyCat

(Posted 2005) [#1]

I'm writing a 2d in 3d shooter (arent' we all :-) and until now I've been using my own collision based purely on the distance between sprites, and it's been working fine.

However, for some reason I though I'd try changing it to use Blitz built-in collision handling. My experiments show that it should work really well apart from the fact that the only collision reactions you seem to have are stop or slide.

I don't really want the player's ship stopping when it hits a powerup, or an enemy ship stopping 'cos a piddly little bullet has hit it, so is there any way of detecting the collision but allowing the entities to continue moving?

fall_x

(Posted 2005) [#2]

I've been wondering about this too.
However, if you delete the powerup or bullet on impact, it works fine.

RiverRatt

(Posted 2005) [#3]

You can use entitydistance. It works just like standard collisions with entityradius but no responce.
Also there is another comand but the docs say its slow.
Its called MeshesIntersect (mesh_a,mesh_b )
oops, your using sprites, so the MeshesIntersect won't work here.

For powerup.powercrystal = Each powercrystal
If powerup<>Null
 	pow_del=0
	For p_ship.player = Each player
		If EntityDistance (p_ship\p_pivot,powerup\mesh)<15 Then 
	 		pow_del=1 
		EndIf
	Next 	
   If pow_del=1 Then   
		p_alpha#=.5
		FreeEntity powerup\mesh
		Delete powerup 
		pow_del=0

	EndIf
EndIf	 
Next

HappyCat

(Posted 2005) [#4]

Cool. EntityDistance seemed a bit ... dodgy - but I hadn't tried combining it with EntityRadius - I'll give that a shot.

Mustang

(Posted 2005) [#5]

only collision reactions you seem to have are stop or slide.

Yup. Those are your choices with built-in collisions:

http://www.blitzbasic.co.nz/b3ddocs/command.php?name=Collisions&ref=3d_cat

HappyCat

(Posted 2005) [#6]

RiverRatt:

That's pretty much exactly what I'm doing at the moment except I've been using my own distance calculating routine. I've changed it to use EntityDistance instead and it's still working fine.

The reason I fancied trying collisions is that it copes nicely when the delta timing stutters when sprites move past each other in a single frame. But the stopping behaviour doesn't allow for the way I've done the players bullets (if an enemy is weak enough, a bullet can destroy them and then continue).

I'll just stick with EntityDistance for now and maybe limit the maximum frame duration to 100 milliseconds.

Mustang:

Yes, thank you.