Texture Sizes

[TheC]

I was wondering how non-standard textures are stored in the video memory. If I have a 700x700 texture, will the video card store it at that size, or as a 1024x1024 texture?

[omaremad]

They stay that way, thats why mipmapping is really bad on non pow of 2. No scaling happens and the card just applies the pow of 2 mipmap algo on the strange sized texture.

(Im just guessing by looking at results) You could pull the texture data out of the gfx card manually and see.

[playerdark]

I also notices that on my nvidia card rendering seems to be faster with smaller textures than with large ones. Not sure why that is the case, but its significant.

[AlexL]

playerdark,
In a simple answer to your question, the larger the texture, the more processing and drawing has to be done. Which will slow down the application as it's processing, smaller texture, less processing time and more speed to the application as a whole

[omaremad]

Thats called fillrate, its a common number quoted on tech specs. Also lots of transparent polygons that nearly fill the whole screen use a lot of fillrate ( like slowdown that is common in games when approaching smoke and fires)

so the fillrate expenditure dpends on two things, the texture size being rendered, how the fragments are being mapped to the screen (how big is that texture in screen terms).

[playerdark]

Good point AlexL. I was somehow assuming that each pixel on the screen would just cause the same amount of lookup work regardless of the texture size, since it is the same pixel after all, but maybe that would cause too much visual distoration as texture parts are left out. I'm not very familiar with the way textures are processed, I was more focusing on vertices and the mesh structure with my optimizations, but I guess I have to keep an eye on the texture too. Guess that's what mip maps are for