Jump and Run Collision

[/\/\isanThr0p]

Hi Everoyone
Well I made tilebased Jump and Run games, but I was never happy with the outcome.
I have a slight problem with the collsion detection. I always used to have a tile either be walkthrough or not. Now I want things like diagonal pathes and stuff like that.
So should I use masks for the tiles? Has anyone ever done a fast running program, that used masks for the collision detection?

Than I would need some good code for collision detection anyways, because my code always was a little messy. If anyone has a good sample please tell me.

[Sastraxi]

At VoodooVB (http://voodoovb.thenexus.bc.ca/) there are a few tutorials that discuss the usage of fast rectangular, circular and vertex-based collision detection. I suggest you look into that.

[/\/\isanThr0p]

I am having a look right now
thanks

[Jotaf98]

I'd use rectangular collision for the tiles, and circular collision for the sprites.

A good technique I saw in professional games that use rectangular collision for the tiles is that when the player collides with a wall only partially, he will be moved in that direction (the player will never be stuck in walls, instead he will slip):

The player collides with a wall, but only with his left side

---
  XX

The game automatically moves him/her a bit to the right each frame, so he can pass :)

---
   XX

This is a trick that players hardly notice (so most small games don't have this) and usually makes them happy with your game

[/\/\isanThr0p]

In the moment I am only using rectangular collision and I have that move thing implemented. I would have no Idea how to work without it.
Once the game get's little more interesting I will probably post it so you can see why I need to implement this.
But I still don't know how to implement slopes if I use the rectangular.

[Jotaf98]

Just use a big "If...ElseIf...ElseIf...End If" like I did

Like this:

'If there's a wall in the top-left corner of where the player is moving to, and there isn't in the top-right corner of where the player is moving to...
If DetectCollision(NewPlayerX,NewPlayerY) = True And DetectCollision(NewPlayerX+PlayerWidth,NewPlayerY) = False Then
  'Move a bit to the right. Also don't move up!
  PlayerNewX = PlayerX + PlayerSpeed
  PlayerNewY = PlayerY
End If

That's when the player presses the Up key and you set the NewPlayerX/Y with his new coords. You'll need to make the same thing if the top-right corner is blocked, for when both of the corners are blocked (the player can't move there), and when both of them are not blocked. You'll also have to repeat this for the other 4 directions.

I know it's hard, but with some paper and a pen you'll get there

[/\/\isanThr0p]

no I got all that long ago, but my problem is tiles that have slopes.
somethig like this:

_______
\
\______________/

I need collision with the tiles that have different slopes!! I probably have to use masks.

[Jotaf98]

Nope, masks is a bad idea - it's too slow and you can get the same results by using polygon collision detection

[/\/\isanThr0p]

I kind of doubt that the polygon collision detection would be more efficient on tiles, than masking.
Does Anyone know Jazz Jack Rabbit 2 I believe it uses masks.

[Jotaf98]

Read the article, you'll be convinced after you do it

You'll still have to use rectangular collision before looking at the mask's pixels, you're not gonna loop trough all of the pixels of the map every time you wanna detect a collision, are you?!

[Jotaf98]

Ok... what I was trying to say is: before looping trough EVERY pixel in a mask to see if it's colliding with the player, you still have to perform a basic rectangular collision detection - otherwise you'd have to detect collision with ALL of the tiles in the map using masks, which is a very slow process! This way you can by-pass some of them if there isn't a rectangular collision

Ah, forget about it, it's in the article on collision detection with masks

[/\/\isanThr0p]

Well yeah I will have a closer look into all of that.
Thanks

[Jotaf98]

You're welcome

But if your game gets too slow, you know where the problem is

[/\/\isanThr0p]

Well I said I will take a look into all of that and decide for the fastest version of course.