Roland_Yonaba wrote:I love
you that.
thanks!
Roland_Yonaba wrote:
In a nutshell, how does it work (i haven't digged in the code yet) ?
Are you making some sort of space partitionning ?
Ok. Let me try to explain.
Bump divides space into squared "cells". Cells are created "on demand", as needed, so you don't need to specify "world boundaries" or anything. Empty cells get garbage-collected when the collector runs. They have a default side length of 128, but that can be changed in bump.initialize().
Appart from the cells, there are "items". Items are the objects of your game. The player, bullets, enemies, ground tiles, etc. In bump, at least for now, an item is defined as "something that has a bounding box". Items' bounding boxes can change in position and size over time. This is called "updating". When an item is added (or updated) bump calculates which grid cells it "touches". For each item, it knows what cells it touches. For each cell, it knows what items touch it.
That's the nutshell. Once you have the list of items with their cells, and the list of cells with their items, you can check for collisions very efficiently.
The way the collisions are calculated is relatively simple. However, the
order in which the collisions have to be triggered, is tricky as hell. When a player walks over a tiled ground, is surprisingly complex to tell it "consider the tile right under your feet first", so it doesn't consider the "next tile" as a wall, and stops walking. I think I've managed to get it more or less ok, but it's still not 100% perfect. On 1.2 I've basically redone this whole prioritisation thing, as well as added "static" items (which
At the end, what you get in the bump.collision callback is a pair of elements colliding, and a displacement vector. The displacement vector is literally the smallest movement you have to make in item so it doesn't collide with item2 any more.
Roland_Yonaba wrote:
Actually, bump stand for collision checking with rectangle-bounded shapes. Have you plans to add support for more shapes ? Points, Segments, lines, Circles, triangles, n-shaped polygons ?
I like bump's simplicity. For now, it suits my needs. I don't plan to include shapes. For now, it'll remain bounding boxes-only.
I
do plan to include more types of
queries. Right now you can only say "give me the items on this rectangular region" (with bump.collect). I'd like to be able to say "give me the items containing this dot" and "give me the items on this segment". But I have to think about how to do that properly.
Roland_Yonaba wrote:
Actually I was looking for some little "physics" support...I mean, looking at the attachment, the box should fall. But it won't....
Ah, but the image you have shown could also be a car seen from a top-down perspective, and the block next to it a little building
. Adding physics would overcomplicate the lib IMHO.
Thanks for your comments. Let me know if I can be of assistance in any other thing! (although I'll leave the country in 2 days, and I'll be quite busy until september)
(Do they use canvas?)