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Order or 2D drawable entities

Started by Phenixer Jun 23, 2012 at 3:27 PM 0 replies 1.7k views

Original Post

Jun 23, 2012 at 3:27 PM

Hey Guys,

I was asking myself what would be the best way to order my entities drawn on my map in 2D space.
What I actually do is Draw the map background, Draw all entities (pawns + projectiles) in a given order, Draw the map foreground.
For all my entities, I need to draw them in Y coordinate order.

I could :
1. Order every time I draw on screen, every tick I go trough the whole array (ordered) and reorder using a simple bubble sort and continue to cycle until nothing requires ordering.
2. Order directly in the classes when moving. If an entity moved, it requires reorder.

I do not know much about reordering techniques and I will surely (or maybe?) not use C# LinQ OrderBy method.

Thank you for answers !

SHilbert

Jun 23, 2012 at 10:23 PM

Assuming you are working in C# since you mentioned avoiding LINQ. My first try would be this:

Collect all the entities that are onscreen into a List, and use List.Sort with a custom Comparison method. Don't use bubble sort! If you Clear() and re-used the visible entity list instance every frame, you will not generate any unnecessary garbage this way.

I wouldn't try to do any schemes to sort only while entities move unless you can't get good enough performance this way, just because it is far simpler code to just sort right before rendering. In my experience you can sort a lot of objects this way and it will still be fast.

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