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Simple texture vs. surface question


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#1 jorelmb   Members   -  Reputation: 182

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Posted 20 August 2006 - 02:12 AM

Hi, I'm trying to make a simple renderer for D3D. Now I'm working with 2D graphics so I'm using surfaces and textures. I've read that textures are only for rendering and surfaces are for all purpose. But: For "animated" 2D sprites should I use textures or surfaces? Would it be better to have all the images of an animation in a surface and only changing the RECT at the time of rendering (or a texture) or have a vector of textures containing each image of the animation? Thanks in advance for any help. :)

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#2 ToohrVyk   Members   -  Reputation: 1591

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Posted 20 August 2006 - 02:14 AM

As an alternative, you can also use texture coordinates to select what portion you want within a given texture. This way, you have fewer texture state changes (one texture, different coordinates each time).

#3 blaze02   Members   -  Reputation: 100

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Posted 20 August 2006 - 11:07 AM

First off, textures and surfaces are basically the same thing to the programmer. In DirectX, a texture is what you render from (for texture mapping) and a surface is what you render to (the frame buffer or back buffer). You shouldn't have to worry about the details at all unless you are rendering to a texture (i.e. rendering to a texture's surface).

For animations: there are 2 things to worry about when loading textures.

First you have your video memory. If you load too many textures into video memory, it is possible that the next one will refuse to load. The best advice I can give you for now is, don't worry about memory limits at all for now. You will most likely never reach the limit. The only thing you may want to do is protect your code from a failed texture. Make sure your code will not crash when you access a NULL texture (i.e. read the return value of d3dxcreate call, if it is an error, set the texture* to NULL, also make sure to not ->Release() a NULL texture.

Another great trick to reduce video memory of each texture is to compress the texture. Check the parameters of D3DXCreateTextureFromFile on how to compress the texture in video mem.

Next you have to worry about texture swaps. Every time you call d3d_device->SetTexture(...), you are talking to the video card, which is slow, but it has to be done. You will want to minimize the number of SetTexture calls per frame. To do this, you can put a bunch of images into one large image (a texture atlas), and access each using separate texture coordinates. Again though, I wouldn't worry about doing this. Your animation renders only once per frame, thus, it MUST call SetTexture once per frame. If you wrap all the animations into a single texture, you are still calling SetTexture once per frame. The only downside to having a lot of textures, is the small amount of overhead required in the video card. Each texture needs a bit of video memory to store the format, size, etc.

So loading 16 textures that are 32x32 is going to take up a little more memory than a 512x512 texture. But it is pretty hard work to max out a 64MB video card.

I loaded around a hundred 128x128 textures for an animation and it worked fine. Doing some quick math, thats only 6.5MB with no compression.

I hope that helps. Good luck on the animating.
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