Attached Link: Weird skin artifacts example

I read on here somewhere that you should render as large as you can, then scale down for better results.

So I had a crack at it.

And got this weirdness......

Image link moved to the top because of more weirdness.

If it helps, the model is V4 with the Pretty 3D bodymorph, facemorph and the V4 skin realism kit, and the render size was 5000 pixels high (by nearly as many wide) rendered with FireFly.

Anyone have any clues as to which setting I've knackered?

Wow.  Do you really need a render that large?  The file size will be staggering.  I really think it's overkill.  But those artifacts look very distinct.  They may be from a mat.

Jeez, they look like topographic lines off of a USGS Topo map showing elevation lines!

Almost like a tattoo? Why so big in the first place?

I read on here somewhere that you should render as large as you can, then scale down for better results.

So I went for size = BIGNESS.

I won't be rendering that big again anyway, lol.

Just gonna have to have a squiz through the materials and see if anything jumps out at me.

This is the result from use the "V4 skin realism kit".

If you want to render big, try setting the render dimension to something smaller, like the size of your screen resolution, like 1024 by 533... and set your pixel resolution to like about 300 dpi if you're going to print it. Personally I go by 96 dpi for the screen and the largest I have ever render is 1024 x 1024 and I squished it down to whatever size I need at the moment.

The patern looks like there is something going on in the nodes plugged into the displacement. Does it disappear if you switch of displacement in the render settings?

What version of poser are you using maybe there was some change in the nodes used between versions of Poser.

Have you made any alterations in the material room besides applying the Realism kit?

I am using Poser 7 - and the only render setting I messed with were the raytrace bounces (whacked 'em up to 5 to see what happened).

The material room I left well alone, and I haven't tried turning off the displacement....

For most renders, raytracing should be kept between 2 - 3.  Try cutting back on that and re-render.

What you're seeing is called quantization noise, and is the result of applying a bump map that does not have enough dynamic range.

Bump maps, being 8-bit images (generally) can only take on 1 of 256 distinct values. You may think you're seeing continuous variation in the surface, but this is not the case. The surface bump level is always a stair-step function, with the smallest possible step being 1/256th of whatever your maximum bump value is.

The "contour" lines you see are the edges of on of these levels. The lines are showing wherever there is a "step", for example from 141 to 142.

The reason you see them when you render big is that texture filtering at that size is not needed. So Poser is rendering the bump map exactly, which creates the steps.

When you render at normal sizes, texture filtering applies, and it is interpolating and averaging those values, thus creating the appearance of numerical values BETWEEN the steps, such as 141.23245.

Oh forgot to mention that I see most bump maps made by the naive are almost entirely mid gray or damn close. This means that the full set of variation in the bump map must be encoded into only a handful of values, for example from 126 to 131. Thus, the effective quantization of such a bump map is less than 3 bits, instead of the full 8 bits it should be.

A properly made bump map has black and white in it, not just shades of gray. Then you adjust the bump amount to scale those values into the tiny range you really need for pores and such.

Hi,

This is due to the option "granit displacement" in the skin realism sript. Turn it off and it will disappear.

Thanks for the responses people, it's appreciated :)

Hi, ditto to 'granite displacement', had that problem years ago with this realism kit and after consideration, it was face_off's advice.

regards....