Checking pixels in tmx files

[szmol96]

Hi. I am working on an engine for my later games and I'm using getPixel on a map image for collision detection, but have I realised that if my image would be larger, it would take more time to check for collisions. So I came up with the idea of checking pixels in tmx maps. Is that possible? If so, please tell me how to do it. Thanks in advance.

[Kingdaro]

Checking individual pixels in a map for collision detection is a rather slow way of doing things. Why not use a collision layer? As in, an invisible layer with a bunch of shapes denoting where the collisions are. Something like this:




(from here)

[szmol96]

I know, but I want to experiment a bit with the different kinds of collision systems, starting with the easiest ones to implement. I have tried tile based so far, but I didn't like it, because it didn't give me enough freedom.

[Murii]

Hi. I am working on an engine for my later games and I'm using getPixel on a map image for collision detection, but have I realised that if my image would be larger, it would take more time to check for collisions. So I came up with the idea of checking pixels in tmx maps. Is that possible? If so, please tell me how to do it. Thanks in advance.

Uh what? This is a bad idea for checking collision detection )

[szmol96]

Ok, I will listen to you guys, pixel collision may be slow, but i don't know how to make any other collision system, except tile based. The one with polygons sounds good, but I have no idea how to implement it. Can somebody explain it, including the details?

[micha]

I wouldn't say, that pixel based collision is bad per se. But it is probably not easy to implement.

The same goes for vector based collision. It is not easy to implement. I would rather use a library that does it for me, such as the love.physics module.

This article gives a nice comparison of the general approaches to collision detection.

In the Free Game Resources Section of the wiki you finde some in depth tutorials on collision detection with different approaches.

[szmol96]

Pixel collision will be fine for me, but how can I make it faster if I plan on making huge levels?

[HugoBDesigner]

The problem with pixel collision is that it is slow under most circumstances. Making the computer check thousands of pixels everytime is slow. Are you checking them every frame? If you are, just compare the pixels in an area close to the player (for example, pixels in a radius of 50 pixels around the player). Depending on what you have this can work very well

[Kingdaro]

Pixel collision will be fine for me, but how can I make it faster if I plan on making huge levels?

That's pretty much the tradeoff of using such an expensive algorithm. Either keep your levels small, use polygons, or don't use LOVE.

Depending on the level of detail and intricacy in your game, a good method for you would be to use the love.physics module along with using tiled maps with a library like STI, then using object layers in Tiled for collision zones.

[szmol96]

The problem with pixel collision is that it is slow under most circumstances. Making the computer check thousands of pixels everytime is slow. Are you checking them every frame? If you are, just compare the pixels in an area close to the player (for example, pixels in a radius of 50 pixels around the player). Depending on what you have this can work very well

I only check pixels around the player and at some bullets' position. Is that still slow?