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Batching (custom) sprites

Started by Trillian Jul 6, 2006 at 8:01 AM 1 reply 450+ views

Original Post

Jul 6, 2006 at 8:01 AM

Hello Gamedev! I'm developping a 2D engine and I'd like a way to batch my sprites so that my rendering is more efficient. Currently, I'm doing the following, which I am pretty sure is a very slow technique : - Hold a MyVertexStruct array of four vertices (simply MyVertexStruct v[4]) - When rendering a sprite, set the four vertices and call Device->DrawPrimitiveUP(D3DPT_TRIANGLESTRIP,*,*,*); I still manage to show a couple of thousand of sprites/particles on screen but I'm sure there are better ways to do this. I've thought about using vertex buffers but I have two problems : 1- I cannot batch sprites with different textures in the same buffer and render them at once. 2- World matrices might have changed between each addition of sprites in the buffer. I've thought of using my first technique for sprites and have a special function StartBatch() to accumulate vertices which share the same texture and world matrix in a buffer (mostly for particle systems), and then call EndBatch() to draw them. Would that be the best way to do it?

jollyjeffers

245

jollyjeffers

Jul 6, 2006 at 8:40 AM

Batching sprites isn't the easiest of challenges [smile]

Can you make use of shaders? There are a number of tricks you can play (based on instancing) that allow you to pack multiple transforms/textures into a single draw call.

I would highly recommend trying the accumulate method you suggest. It'll be fairly trivial to build a sys-mem array of 10/100/1000 sprites (note that you'll have to use triangle lists (6 verts) instead of strips) and despatch them as a single call. Simply reducing the number of API calls (especially drawing ones) should yield a nice speed-up.

Also note that you might be able to use D3DXVec4TransformArray() (or the Vec3 form) to do CPU transformations. That way you can group based on effect/texture rather than worry about transform.

Also consider any frame-coherancy... does each sprite change/move EVERY frame? Why do any more work than is necessary?

hth
Jack

Trillian

Author

Trillian

Jul 6, 2006 at 8:48 AM

Thanks a lot, I think I'll go with this method.

Transforming my buffered vertices with the current world matrix is a good idea. When I'll render the batched sprites, I'll simply need to set my world matix to the identity but keep the view/proj matrices, right?

As for the shaders, my engine supports them but I'd prefer not rely too much on them.

Anyways thanks for your confirmation

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