How to reduce the number of gameobjects used for representing building blocks

Question

I'm developing a 2D building game for mobile devices where it is possible to spawn building blocks by touching the screen. At the moment each of those blocks is represented by a gameobject that has a sprite renderer and a physics collider attached. The problem is that I need up to 20000 of these blocks in the scene at the same time. That might sound a bit much but there are some restrictions that ensure that the game still performs pretty well. So my problem isn't performance related in terms of physics or rendering, it's just the mere number of gameobjects that gets me into trouble. It doesn't matter if I use my building blocks or just empty gameobjects, after instantiating several thousands of them every additional instatiation takes forever.

For that reason I'm trying to cut down on the number of gameobjects used in my game by combining some blocks into bigger gameobjects. Unfortunately I can't figure out how to get this right.

I read that in Minecraft-like games several thousand blocks are combined into chunk meshes (using one mesh collider) that can be rebuilt whenever a block is deleted but as far as I can tell that is not possible using sprites. Also I think it might not be sensible to follow that approach since my blocks are not necessarily aligned next to each other and therefore there would have to be some holes in the mesh. Has anybody tried to achieve something like this, or do you have any ideas on how i might approach the problem differently?

Any suggestions would be appreciated!

Answer 1

Best Answer

Answer by TonyLi · Nov 10, 2014 at 02:47 PM

This is one scenario where I'd recommend addressing efficiency from the start, since this will end up being a fundamental design issue, not simply an optimization issue. 20,000 blocks in a scene will never be practical. Here are some suggestions:

Combine blocks. If you have a 3x3 pattern of blocks, replace it with a single 3x3 GameObject. If you need to break them apart at some point, replace them with the individual blocks only at that point.
Use space partitioning, such as a quadtree, and only spawn GameObjects within the player's immediate area. I write "spawn" instead of "instantiate" because you should use object pooling for this. So the full map will be in memory (an abstraction), not in the scene.

Also, as a final suggestion, consider posting open-ended questions like this on the Unity Forums instead of Answers. In Answers, you'll get better responses for cut-and-dry questions. The Forums are better for discussions.

Add comment · Show 3 · Share

Habakuk · Nov 10, 2014 at 03:43 PM 0

Share

Thanks for your suggestions! What you mentioned in your first point is what might be sensible in my situation but I don't know if it's even possible. I guess my original text boils down to the question if and how I could combine several gameobjects that each contain a sprite renderer and a physics collider and that are not perfectly aligned next to each other (meaning that there will be some holes in the resulting mesh/collider). I would like to know if it makes sense to put time and effort into this endeavor or if I should just abandon the idea of combining blocks.

TonyLi · Nov 10, 2014 at 03:57 PM 0

Share

Yeah, you're going to have a hard time with the first point if the shapes are irregular and unpredictable. You could try to stitch meshes together into a single mesh, but in the end I think it wouldn't be worth the significant extra complexity.

Point two will probably give you much more bang for the buck.

Habakuk · Nov 11, 2014 at 09:27 AM 0

Share

Your answer might not have been what I hoped to hear but what I needed to hear. It helped me decide how to go on with my project. I'll wait a few more hours and if nobody comes up with an unexpected genius solution I'll mark your answer as accepted.

How to reduce the number of gameobjects used for representing building blocks

1 Reply

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions