So I'm developing a 2D tile game.
To avoid having to make a huge amount of draw calls every frame, I render my tiles to textures of about 512x512 when loading the map.

In the game loop I then only have to draw a few of these textures on screen every frame.

I was quite happy with this method as my render method went from 15ms to 3ms.
But when I tried this approach on larger maps, my render method sometimes took over 20ms. (not constantly, it was more like: 3,3,4,3,4,28,3,3,3,3,4,3,3,3,4,34,3,3)

When I analyzed my application with visual studio I got the warning that I was pageing an extremely high amount of active memory, sometimes over 5000 pages/sec.

So the problem is that I can't just load the entire map into small textures as I can't store all these textures in the memory at once.

As I see it, the only way I can solve the pageing problem is by going back to my old strategy of drawing all tiles seperately on screen every frame. But I don't want to lose performance again... Does anyone know of an alternative or maybe a way to combine both approaches that I have tried.

Thanks for the replies. Let me describe my render method in greater detail to clear things up a bit.

tile size: width 64, height 32 (diamond shaped, stored in a png of 64*64)

small map: 32 tiles * 128 tiles = 4096 tiles
normal map: 64 tiles * 256 tiles = 16384 tiles
large map: 128 tiles * 512 tiles = 65536 tiles

Now since my tiles are diamond shaped I draw a tile every 64 pixels on the x axis and every 16 pixels on the y axis.

small map: (32 tiles * 64 pixels/tile) * (128 tiles * 16 pixels/tile)
-> map size = 2048px * 2048px
normal map: (64 tiles * 64 pixels/tile) * (256 tiles * 16 pixels/tile)
-> map size = 4096px * 4096px
large map: (128 tiles * 64 pixels/tile) * (512 tiles * 16 pixels/tile)
-> map size = 8192px * 8192px

As you can see even the smallest map has a size larger than most screen resolutions so not all tiles have to be drawn on the screen.

When loading a map at the start of the application, I:
1) divide the map in chunks of 512x512
2) create a render target texture of size 512*512 for every chunk (I'll call it a supertile)
3) draw the right tiles on the right supertile

In the main game loop I then draw the supertiles that are in view on screen. If a supertile is only partly in the view, I draw just that part (using a rect).

Performance is very good since for a screen resolution of 1024*768, at most 9 supertiles will be in the view, so only 9 draw calls are made per frame.
But as I said performance for larger maps is bad due to memory bounds. Loading a map of 8192px * 8192px in memory is just too much.


@buckeye:
- not all tiles are unique, I only use 64 different terrain sprites.
- tiles that aren't in view aren't drawn
- I don't need 512*512, but since I'm loading the entire map in the memory (8192*8192) it won't make a difference if I do it in pieces of 256*256 or 512*512. If I take a smaller supertile size I will just have to use more supertiles so in the end I will use the same amount of memory.
- supertiles have 1 mipmap level

@lorenzogatti
-the textures/supertiles are used to assemble into large pictures
-a buffer to replace seperate calls sounds like an interesting idea. Any links to some info on that topic will be appreciated.

I will do that, thanks guys. I Should probably do some more research before I start programming next time. It took me quite some time to get those supertiles working before realizing that it wasn't very realistic.

Quote:Original post by TaxCollector
But when I tried this approach on larger maps, my render method sometimes took over 20ms. (not constantly, it was more like: 3,3,4,3,4,28,3,3,3,3,4,3,3,3,4,34,3,3)

When I analyzed my application with visual studio I got the warning that I was pageing an extremely high amount of active memory, sometimes over 5000 pages/sec.

I've been strugling with exactly the same problem that every X frame takes so much longer to render.

How do you create your textures? I use D3DXCreateTextureFromMemoryEx(). Initially I used the D3DPOOL_DEFAULT pool for the textures, since it looked like it uses much less system memory. I changed it to D3DPOOL_MANAGED, and the problem of swapping memory in and out was gone and my framerate increased by 3x what it previously was. I does use more system memory now, but that I can later sort out with 64-bit programming to use more mem ;) hehe

I would like to know if this fixed your problem.

Well since I first render my tiles to texture, the textures are D3DUSAGE_RENDERTARGET and that flag is only compatible with D3DPOOL_DEFAULT. So that may contribute to the memory problems.

I'm now drawing my on screen tiles with 1 DrawIndexedPrimitive call using a vertex and index buffer and 1 SetTexture call using a terrain atlas (512*512).

All in all I'm quite happy with the performance:

pc 1: ATI radeon HD 4850 @ 1920x1200

rendertime: 2ms-3ms

pc 2: NVIDIA geforce 6600 @ 1024x768

rendertime: 4ms

laptop: NVIDIA geforce go 7300 @ 1280x800

rendertime: 18ms

What bothers me is that my laptop can't even get 60 fps. With a resolution of 1280x800, 1 DrawIndexedPrimitive call that draws about 2000 triangle primitives takes 18 ms. If I turn on vsync fps drops to 30. Am I expecting too much? 2D tile games have been in existence for years and even PC's back then could manage..