Clean skin Iray help

OminousAutumn

I cannot seem to get particle free skin with my Iray renders in Daz 4.8. Can you recommend the key factors to getting good looking skin, smooth and clean skin as in the examples on the website? I have plenty of light in my scene so I dont believe that is the problem. Is it a matter of applying a shader that i am not doing? Is it the max samples? render quality? The screen shot shows my render setting and even after 8 hours there is still noise. Is it just a matter of time, some renders take close to 24 hours to be crystal clear? Any tips for an overall workflow to achieve clean skin would greatly appreciated. Thanks!

Oso3D

I would suggest hiding everything but the lights and one figure, see how it renders. What convergence is it showing?

Szark

lets go back to how you set the scene up, which is probably where this issue lies.

Do you convert all the materials to Iray yourself or just let DS do it. If you did convert then did you set up each surface proerly as the conersion isn't always right.

Wat does the scene contain in terms of lights and props. Is the camera looking through glass?

fastbike1

It's not render time. Even with CPU only I have had clean renders within the default 2 hours. With GPU, single figure and background I get clean renders in 2 to 10 minutes.Default 95% convergence.

Are you sure you're using Iray shaders?

Tobor

Is that a water (shower?) scene? First thing to do is to hide the water geometry, which -- depending on how it was done -- severely impact rendering times. Will's suggestion is spon on. You can only troubleshoot these issues by reducing the scene to its bare essentials, then build back up.

Finally, define "lots of light." That's quite subjective. In the end, you may have "lots of lights," but in total they do not provide very might illumination. 

OminousAutumn

I do NOT convert all the materials to Iray myself. Does that involve highlighting everything and then selecting the Iray uber base? Even for skin or do you use Human surface base for skin? The camera is not looking through glass. The scene is lit by 11 point lights with lumen values around 5k and intensity values ranging from 5-25k. Does the speed of the computer not determine the speed of the render as well? Should my specs (see attached) allow me to render a clean image in around the same time of 2 hours? Convergence is set to %98 with a Quality setting of 1. Thoughts...?

fastbike1

For Iray, the intensity setting in a light is ~meaningless. Luminous flux is the parameter and the units aren't lumens as you are thinking of them. Your lumen values will need to be increased to 30000 or more, You may not need that many lights either.

For the skin, select the character, then in surfaces select the skin. Use the Iray Uber shader if you don't have specific iray shaders for your character.

OminousAutumn

ok cool, many thanks!

Tobor

stillmovingstudios said:

I do NOT convert all the materials to Iray myself. Does that involve highlighting everything and then selecting the Iray uber base?

Well, someone has to change the shaders to be compatible with Iray. If you don't do it yourself, then it's done automatically using a process you have no control over. There's no telling what you'll end up with. There's no way the automatic conversion knows "skin" from "rock" from "water droplets." You get what you get, which is usually not what you want.

It does involve selecting the individual objects and applying the appropriate Iray shader that best approximates the material you are trying to reproduce. It's tedious, but it's hot you get the best results.

11 point lights is probably 8-9 too many lights. Try your scene with an HDRi in the Environment, and a carefully positioned spotlight (or pointlight) or two coming from the side to rear-side to catch the water droplets.

Someone once said "Iray likes lights." That's true, but it also means longer render times. Each light requires separate ray tracing calculations, which can sometimes involve dozens of bounces off different reflective objects in the scene. That's a lot of math to do, because it has to be repeated for every pixel in your image. Not only that, every pixel is processed this way many, many times over.

Your system isn't particularly spectacular as an Iray rendering engine, so help it by simplifying the lighting. Set each light source so it emits enough light to adequately illuminate the scene. Iray does best in brighter lit sets. The dark areas take longer for the pixels to "converge" -- convergence is a process that involves comparing dozens, hundreds, and even more separate light samples, with the results of previous samples for any given pixel. The process takes longer in darker scenes, or in heavy shadow. Incompletely converged pixels have that grainy salt-and-pepper look.