A Little Collision Help

BlitzMax Forums/MiniB3D Module/A Little Collision Help

Matt	(Posted 2008) [#1]

I'm hoping someone can help me out here. I've started a very basic 3d game (my first one) and I'm having a bit of trouble with collisions.

I have 1 mesh for my player, and it is given EntityType 1, while my buildings are EntityType2.

Now, when I setup Collisions 1,2,3,1 or any other combination of 1,2,#,# nothing happens. Now, I control the movement of my player with WASD movement, so maybe I'm messing something up here, but how exactly do I check for collisions then?

Also, I've noticed that Collisions 1,2,2,2 requires a sphere radius to be applied, but how does this work with tall, slim type meshes? The hit boxes would be very off.

I can post my code if needed.

Thanks

simonh

(Posted 2008) [#2]

* Use Collisions 1,2,2
* Use EntityRadius x,y for an ellipsoid
* Make sure you are using UpdateWorld once per loop.

Look at the sliding_collisions.bmx for an example.

Matt	(Posted 2008) [#3]

Thank you, that worked great!

Matt	(Posted 2008) [#4]

Alright, maybe I spoke too soon. I am no longer using CreateCube, but rather a mesh that I exported from Blender.

I have the following for TShip:

' 3D Entity
		s.mesh = copymesh(efactory.shipMesh)
		s.texture = efactory.shipTex
		EntityTexture s.mesh, s.texture
		PositionEntity s.mesh, 0,0,0
		EntityType s.mesh, SHIPID
		ScaleEntity s.mesh, s.sizex, s.sizey, s.sizez
		EntityRadius s.mesh, s.sizex, s.sizey, s.sizez
		TurnEntity s.mesh, s.xrotation, s.yrotation, s.zrotation

and for TAsteroid:

a.mesh = CopyMesh(efactory.asteroidMesh)
		a.texture = efactory.asteroidTex
		EntityTexture a.mesh, a.texture
		EntityRadius a.mesh, a.sizex, a.sizex, a.sizez
		PositionEntity a.mesh, a.x, a.y, 0
		EntityType a.mesh, ASTEROIDID
		scaleEntity a.mesh, a.sizex, a.sizey, a.sizez

Both are created with PositionEntity a.mesh, x, y, 0 as to keep the Z axis out of the picture.

SHIPID = 1
ASTEROIDID = 2

by calling

Collisions 1,2,2

I really only care about the Entities that collide, so I've tried EntityCollide and CountCollisions to see if my ship has collided with anything. Neither are correct.

Any ideas?

simonh

(Posted 2008) [#5]

Collision mode 2 is only intended for use with dynamic ellipsoids -> static meshes. If your ship and asteroids are both moving, you will have to use method 1 (sphere-sphere).

Use Collisions 1,2,1 for this.

Matt	(Posted 2008) [#6]

I'm sorry, I forgot to mention that I tried that method as well. Should countCollisions or EntityCollide be returning correctly in either of these situations?

Matt	(Posted 2008) [#7]

Great, I figured it out. I was altering my ship.x based on my own coordinates and not the EntityX/Y/Z ones.

Learn something new everyday...

Matt	(Posted 2008) [#8]

Ok, well, this still isn't working and I'm very confused as to why. Perhaps I'm doing something to break something...

My ship is positioned at screehwidth/2, screenheight/2, z=0

The ship actually never moves, but everything else is adjusted by is velocity. So, an asteroid is moved -x,-y of the ships velocity direction.

When an asteroid is moved, I call PositionEntity, does that have an effect on anything? Also, I use CopyMesh for my asteroids, does that affect collisions at all?

I've printed out the EntityX/Y/Z of all objects and I can place my ship directly over an asteroid and the coordinates are correct, but nothing happens.

Does EntityCollided not work with collisison?

I am calling EntityCollided(self.mesh, ASTEROIDID), is that not correct?

Any ideas?

simonh

(Posted 2008) [#9]

If you send me the program I'll take a look.

Matt	(Posted 2008) [#10]

I sent you an email with the code.