iRay Final Render Skin Normals different to iRay Preview

Gen3dx

I'm getting the weirdest error that is preventing me moving forward with a new figure (Kayla HD Remake from RareStone).

The skin in the iRay preview looks just perfect, but when I go to final render, the normals appear to be massively exaggerated, creating a horrible finish. I have turned down normal and bump strengths in the skin of the figure, but this has made no difference.

Has anyone seen this behaviour before? And/or any suggestions on a fix?

 

Richard Haseltine

Please zoom in more or give the figure some clothes, post-worked boxes are not an Acceptable Way of Handling Nudity

Gen3dx

Apologies. Images cropped.

Well I seem to have found a workaround. I saved the full material preset of Kayla, then took another character and changed the full body morph sliders to Kayla's, and I have good working skin that finally renders again.

I am still wondering, however, why the Kayla base character would throw up a weird artefact like that, since doing a full copy and paste of the skin materials onto the new character fixed things, implying that there was nothing wrong with the materials, but something else?

mwasielewski1990

bjr21185 said:

Apologies. Images cropped.

Well I seem to have found a workaround. I saved the full material preset of Kayla, then took another character and changed the full body morph sliders to Kayla's, and I have good working skin that finally renders again.

I am still wondering, however, why the Kayla base character would throw up a weird artefact like that, since doing a full copy and paste of the skin materials onto the new character fixed things, implying that there was nothing wrong with the materials, but something else?

The image on the left has clearly the HD morph turned on, while on the right you have the base geometry or not enough subdivision to show the HD details.. HD characters usually come with 2 head morphs and 2 body morphs. The actual "HD" morph requires subdivision of 3 or 4 to be even visible, so that's why in the final render it's visible, and in the preview it's not. Select the character, and In the Parameters pane, look for "Subdivision Level" and "Render SubD Level" parameters. By default, most HD characters will come with these set to "Subdivision level: 2" and "Render SubD Level: 4", meaning in the preview, you'll see a simplified version of the geometry, while in the actual render the model is going to be subdivided additional 2 times, showing all the skin pores, creases and other detail.

If you want to see the same results both in preview and in render, set these two settings to the same value.

Gen3dx

@mwasielewski1990 perfect answer. Thank you! I found the "turn on/off HD Details" within the character's settings in the Content Library, and indeed if I turn off HD Details, the skin looks good again in final render, and your comment about it looking different in final to preview due to differences in SubD display settings makes sense.

I found the SubD settings you mentioned in the character's Parameters. I guess I'll need to play around with these in order to find a combination of settings that doesn't make the skin look plastic and ugly. Or just leave HD Details turned off. I think they're only useful for super closeup shots.

mwasielewski1990

bjr21185 said:

@mwasielewski1990 perfect answer. Thank you! I found the "turn on/off HD Details" within the character's settings in the Content Library, and indeed if I turn off HD Details, the skin looks good again in final render, and your comment about it looking different in final to preview due to differences in SubD display settings makes sense.

I found the SubD settings you mentioned in the character's Parameters. I guess I'll need to play around with these in order to find a combination of settings that doesn't make the skin look plastic and ugly. Or just leave HD Details turned off. I think they're only useful for super closeup shots.

I'm happy I could help :)

A "correct" SubD value is actually only a matter of how good your computer is. For non-HD characters (or for HD characters with HD details set to OFF) SubD 2 seems to be perfect. For HD details, it needs to be 4 or 5 (but 5 is rather extreme and might crash your computer if it's not too powerful)  in order to see the smallest skin pores.

Try rendering with HD details ON and change the "Render SubD" parameter to 4. Judge for yourself if the detail looks good or too "artifacty" but be aware that subdividing the geometry also increases render time, VRAM usage on the GPU and RAM usage on the system in general.

Also, in rare instances, if you have even a non-HD character with Subd = 2, you might see "jagging" appear on the surface of the skin with some HDRI light products, especially with something like a very bright sunlight HDRI. This is the only scenario when I found that pushing the Render SubD parameter in non-hd character to more than 2 makes sense.

Gen3dx

Excellent advice. Thank you. I will look more at tweaking these settings and seeing the results. Not *too* concerned about performance as I have a powerful system (64GB system RAM, RTX3090 with 24GB...)

I learned something new and important today because of this initial problem, so this should improve the quality of my results! I guess we're always learning new things about this complex craft!

Dolce Saito

mwasielewski1990 said:

Also, in rare instances, if you have even a non-HD character with Subd = 2,

you might see "jagging" appear on the surface of the skin with some HDRI light products, especially with something like a very bright sunlight HDRI. This is the only scenario when I found that pushing the Render SubD parameter in non-hd character to more than 2 makes sense.

 So, this was the culprit. I thought it was one of the nvidia iray updates that broke some sort of pathing algorithm or something. Btw, this can even happen on default environment setup, so I will give this a try. Learned something today. Thanks!