larger vs smaller texture sheets

[noob24]

obviously larger sheets are more resorse intensive but my questions are as follows.

1: is it only the area on a texture sheet that is actually uvw mapped too( so any blank areas are not counted and dont impact resorces) that counts ie the actual square mm used precisely or is that irrelevant and its the full size of the sheet that counts when ever referenced by an objects uvw mapping..

2; is it a one time impact per sheet or does it get multiplied each time an objects uvw map references that sheet.

3: should pure colours be given their own individual sheet (ie 64 x64) or is it less resouse hungry to make a small square on a pre existing texture sheet and reduce the mapping to fit the square.

4: if the pure colour is to be used for a transparent texture is it best to keep all transparent or crome effects on one sheet for resource impact reasons

5: would one large packed texture sheet (ie 2048 X 2048) be less resorce hungry than 2 smaller (1024 X 1024) sheets

thanks to anyone who can shed some light on any of these

n

 

[hcornea]

1) The texture is loaded, and the mapping is rendered so both the size of the sheet and the number of UVW verts will matter

2) the number of tverts is dependent on a number of things .. including mapping (welded contiguous areas are, in theory, more efficient) also, the smoothing applied to a model, and the anglle between faces (normals) will determine whether a new set of tverts is rendered.

3) pure colours should absolutely be mapped to a common, or an existing texture sheet (call me extreme, but I think untextured materials should never be used in a modern FS addon) Always use a portion of a texture to minimise drawcalls.

4) If the material is animated, then numerous smaller textures for each separate part is likely to be better. For non-animated (scenery) objects, then common material properties should be grouped into a single material (and used across different models)

5)2048 x 2048 is actually equivalent to Four 1024 sheets. This is "more efficient" but if the sheet requires (has) mipmaps then FSX will not load the full-resolution texture unless a customised entry is present in fsx.cfg on each users computer. In practice this is a bit of a pain. For practical purposes ... 1024 textures if MIPS are required, up to 4096 if they are not (for more real-estate)

 

[noob24]

hcornea

thankyou for the detailed response most helpful

n

 

[lionheart]

I have found that 32bit textures are harder on a machine, while double sized 'regular' 16bit textures are more easily run. I dont know why. Perhaps the code for a texture in 32bit is more 'reading' and a double or quadruple sized texture at 16 bit is 'less' reading on behalf of the chip.



Bill

 

[hcornea]

I guess there's 65,535x the amount of information in a 32bit texture.

I'm sure it doesn't multiply out that way, but the difference between performance of a Windows desktop in 16bit mode - vs -32 bit mode can be pretty impressive on marginal graphics chips. So maybe that's a valid comparison.

So yeah ... less work.

It's not a bad tip for simple coloured objects perhaps. I must confess, I use 24bit RGB or 32bit RGBA dds files for everything.

I might investiage 16bit conversions to see how they pan out.

 

[Mr.FaosFX]

Some games are already using 128bit textures ... the benefit is improved performance but on low end systems, a bottleneck will result, so you have to choose wisely.