I recently saw a thread here that had an interesting tip on texture maps.  Basically (if I recall correctly) it said that we use larger texture maps than a necessary for a decent render.  I cannot find the thread or post.  But was wondering if someone in the know could elaborate.  I stumbled on a set of texture maps that were given away as freebies to create commercial or personal characters ... they are 1095 x 1095 ... and I've been creating a large variety of international characters ... using bumps and specular maps from other sets and base mats from these smaller ones and it seems to work ... and reduce render time.  Am I significantly reducing the quality of the character by doing this?  I plan on fine-tuning these characters for the marketplace.

These are samples using the lower size maps.

As usual I appreciate all the help I can get.

Boni

The one thing that jumps out to me right away are the brows.

Laurie

Those are separate.  I'm using a separate transparency and alpha in the transparency node to create more realistic brows ... some need to be tweaked.  It's the texture base itself that I"m concerned with.

The resolution is really dependent on how close, or distant, the texture will be view in a render.  Head and shoulder portraits benefit from higher resolution texture maps while waist to head or full body renders would appear acceptable with medium res maps.  If the model is a background filler, use a lower res map and minimize displacement, bump and specular effects. 

The resolution you need depends on how big your render is and how much of the render the skin takes up in the picture.

If you're doing a 3000 x 4000 pixel render of a head shot, 1024 px resolution head textures will not look good. But they'll be fine for a character who is in the distance.

Are you significantly reducing the quality of the character by using smaller resolution base textures? Yes. People who do big renders for print won't be able to use them for portraits. Is that a lot of people? I have no idea. All I know is that the current standard in the marketplace seems to be around 4k x 4k for skin textures, so that's probably what people expect when they buy a character.

On the other hand, since they'll probably be fine for most people who only render for the web, you could maybe market your textures as lower resolution textures for much less memory intensive renders. :)

Standard 3D Texture sizes are:
512x512
1024x1024
2048x2048
4096x4096
8192x8192

A 1095x1095 map will consume the same memory as a 2048x2048 map but deliver about half the quality.

As a generic rule, for an object in your render, the amount of pixels you see on the render requires at least twice that amount on the object.

So, let's take a head taking 2/3 of a portrait render of 1500x1500. So the diameter of that head equals 2/3 x 1500 = 1000 pixels, hence the circumference of that head equals pi x 1000 = 3500 pixels (rounded) and according to the rule mentioned above this has to be doubled: 7000 pixels of the texture map should cover the head.

In a full body render however, the same head will only take say 1/10 of that render. So the head will require a 2x pi x 1/10 x 1500 =  1000 pixel wide map.

For short: the 3k or even 4k texture maps that come with the characters nowadays are (more than) fine for close ups shown on screen, but will fall short for high quality large scale prints (A4 size requires a 2000x3000 render => say a 10.000 pixel wide texture map for a facial close-up).

In the examples shown above, the head has a 500 pixel diameter and would therefor require a 2 x pi x 500 = say 3500 pixel wide map for good quality. Half of that ignores the rule-of-2 and would result in modest quality, and the 1k wide map actually used is even half of that. The result says it all. But show the character full boy in context, and the 1k map will do fine.

Edit: plus - following vilters: the 1095 should be shrunk to 1024. 

Wonderful information guys. To take this to the next step ... If I were tto enlarge the base texture to 4000x4000 then add skin details mild blemishes ( moles etc.) Could this upgrade the texture to marhet quality?

Of course. You even can make skin textures from scatch, using noise and marble patterns and appropriate color mixtures and some free merchant resources for eyes and lips and paint a bit yourself plus a few contrasts filters and whatever comes along. So it won't hurt to use the low res image for a start as well, blur it a bit, and so on.

Please add some bump/displacement maps and appropriate specular maps as well, and perhaps even maps that control SSS.

have fun 

That's great!  I can start with some freebies and move ahead.  That is great news.  By the way, aRtBee I did what you said pretty much in those first renders at the top of the thread.  Now I know I'm not wasting my time and efforts. :)

Boni

P.S. The readme on the freebies did give permission to use on commercial creations.  So, I've got all my bases covered.

I looked more closely at some of the textures made by my favorite vendors. Hah. Indeed, some of them do use different resolutions for base and details, and some of them have taken a base that is basically pretty smooth and then added texture in a graphics app to create the illusion of pores and so on. Doesn't necessarily look that great on the flat texture, but still looks great on the model when rendered -- even at pretty high resolutions. So, yes, if you take some time to properly blend all your different parts, maybe add some texture to the skin, plus bump, specular, and displacement where needed, you'll be good to go.

Does anyone know if there's any software to turn photos of real people into textures that will fit various characters?  I've been mucking around on low-res with brute-force resizing, pasting and using clone brush to smooth the edges in but it would be nice to know if there's any kind of short-cut.  Thanks in advance....

Google : youtube => Blender => Projection painting.
Lots of tutorials on Blender projection painting on youtube

Thank you!