Using lower resolution textures with the full resolution in one scene

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Recently I've been using low-res versions of Genesis 8 characters for background actors.  I dial the Resolution Level to Base and Cut the Subdevision to zero.  The question comes from textures.  I've been using low res versions of textures in an effort to reduce the VRAM load.  But I was wondering:

If I load in two idential copies of an object ( a prop or a Genesis figure) and render it, does the VRAM load two copies of the textures or does it 'share' the texture map?  If I use lower resolution textures on one of the objects am I actually using more VRAM?

Basically I'm trying to figure out if it's worth it to use the lower resolution or if I'm better off using a full-resolution texture that is also in a main character and just drop things like specular and bump maps.

 

Thanks for any information on how this works!

Edit & Update: For the next person that comes along.  Iray only loads any given texture file once, even if multiple objects/surfaces use it.  Creating a lower resolution file for background people/props only makes sense if you're not going to use the higher resolution one also.  For example:  You have five walls that all share a diffuse texture and one of them has to be high quality as it will be in the main shot.  Go ahead and use the high quality texture on the others as well.  It's only one file.  If you create a lower resolution one for the others, now Iray loads both the high and the low.

margrave

If you have a lo-rez texture and a hi-rez texture, they're considered as two separate textures. However, if you apply the same lo-rez texture to multiple characters, it will only be used once. AFAIK, it's determined by what file path the texture is at, hence that big list of files when you right-click on a texture map socket. If a texture is already used in a scene, there should not be any penalty to using it again.

Richard Haseltine

Iray gets each map only once, so adding a low resolution version would actually increase the load. As margrave says, there is no doubling up by using the high resolution version throughout since it is already there.

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@margrave and @Richard Haseltine.  Thank you for clearing this up.  I suspected that I was going about things wrong and have started to change my approach.

After reading this post about filling rooms with people, I've built background charactes using a G8 base with only a diffuse texture, then Decimator-ed ("Decimated"?).  I drop a few in, generate a couple of instances to scatter around, and Bob's your uncle a full set of background characters just out of focus.  I might use billboards for larger groups, but this is working so far.

Thanks again!

margrave

Windamyre said:

@margrave and @Richard Haseltine.  Thank you for clearing this up.  I suspected that I was going about things wrong and have started to change my approach.

After reading this post about filling rooms with people, I've built background charactes using a G8 base with only a diffuse texture, then Decimator-ed ("Decimated"?).  I drop a few in, generate a couple of instances to scatter around, and Bob's your uncle a full set of background characters just out of focus.  I might use billboards for larger groups, but this is working so far.

Thanks again!

I wouldn't recommend using only the diffuse. Iray is a PBR engine, it needs the other maps to determine how light bounces off an object. Without them, your figures won't reflect light properly, even if they're just in the background. At far distances you can get away with not having a bump or normal map, but for sure keep the roughness/specular map.