A strange effect when I render with 3Delight

BurritoIncognito

Sometimes when I render a scene the finished image will have a pale, creamy sort of look. It seems to happen when I'm rendering a scene that has a lot of polygons. Attached is an example of a render that has the effect. Does anyone know of any technique I can used to avoid having this effect in my renders?

Oso3D

Check the skin material fo Velvet.

It's a popular setting on a lot of skins meant to emulate fine hair or maybe some element of sss.

And I think it looks like garbage.

My recommendation is to shut it off and, if you want more skin realism, maybe experiment with low levels of reflection.

Sven Dullah

You need to somehow narrow it down, too many unknown factors. If you re-render the same scene, will it be ok or does it always have that look? It could be your render settings, gamma settings for diffuse maps, lights, camera headlamp is on... I render in 3DL and I have never noticed that the polygon count would influence the outcome, it either renders or it crashers because you ran out of RAM:) Do some testing next time you encounter the issue!

BurritoIncognito

It doesn't happen just with skin. Under some circumstances everything in the frame will be covered with the effect, including buildings. 

Sven Dullah

Quick question, what is your gamma settings in teh render settings editor?

BurritoIncognito

Sven Dullah said:

You need to somehow narrow it down, too many unknown factors. If you re-render the same scene, will it be ok or does it always have that look? It could be your render settings, gamma settings for diffuse maps, lights, camera headlamp is on... I render in 3DL and I have never noticed that the polygon count would influence the outcome, it either renders or it crashers because you ran out of RAM:) Do some testing next time you encounter the issue!

Thanks. I lowered the Gamma and the render looks good now. Now it is time for me to do research on what Gamma is and figure out how I should adjust it when required : )

Sven Dullah

BurritoIncognito said:

Sven Dullah said:

You need to somehow narrow it down, too many unknown factors. If you re-render the same scene, will it be ok or does it always have that look? It could be your render settings, gamma settings for diffuse maps, lights, camera headlamp is on... I render in 3DL and I have never noticed that the polygon count would influence the outcome, it either renders or it crashers because you ran out of RAM:) Do some testing next time you encounter the issue!

Thanks. I lowered the Gamma and the render looks good now. Now it is time for me to do research on what Gamma is and figure out how I should adjust it when required : )

You should always have gamma correction on and gamma at 2.20 for a so called linear workflow. This means you will have the best possible shading for your renders. Just bear in mind: For older 3DL material presets (and poser mats, made with a non linear workflow) you might want to check every opacity map (think eye lashes, hair) and set gamma to 1, (in the image editor).  Generally diffuse maps should have a gamma of 0 and every controlmap should be at 1.

Richard Haseltine

Sven Dullah said:

BurritoIncognito said:

Sven Dullah said:

You need to somehow narrow it down, too many unknown factors. If you re-render the same scene, will it be ok or does it always have that look? It could be your render settings, gamma settings for diffuse maps, lights, camera headlamp is on... I render in 3DL and I have never noticed that the polygon count would influence the outcome, it either renders or it crashers because you ran out of RAM:) Do some testing next time you encounter the issue!

Thanks. I lowered the Gamma and the render looks good now. Now it is time for me to do research on what Gamma is and figure out how I should adjust it when required : )

You should always have gamma correction on and gamma at 2.20 for a so called linear workflow. This means you will have the best possible shading for your renders. Just bear in mind: For older 3DL material presets (and poser mats, made with a non linear workflow) you might want to check every opacity map (think eye lashes, hair) and set gamma to 1, (in the image editor).  Generally diffuse maps should have a gamma of 0 and every controlmap should be at 1.

A linear workflow would have gamma at 1 (no correction applied). However, people using a linear workflow generally use an image format that supports greater colour depth, to allow for later tonal adjustments without pasterisation.

Sven Dullah

Well if I'm not wrong, the renderer internally uses a linear color space, so for that linear render to look correct you need to apply gamma correction to it.

A quote from this article: https://www.vfxwizard.com/tutorials/gamma-correction-for-linear-workflow.html

II. The boring but necessary demonstration of Gamma usefulness

As boring as they may look, the following images demonstrate how our eyes work. Both images are renderings of the same scene. A flat black surface with a white linear gradient starting at the center and growing outward. We expect the rendering to produce a smooth transition from light to darkness, similar to lighting a purely diffuse sphere from the observer's position.

The first image is the straight linear render, while the second one has a 2.2 Gamma correction applied.

This linear image seems to have a contrast peak both in the white center and in the dark outer region. It also looks smaller, while it is of the same size as the other one. Looking at its brightness histogram, we can verify it is indeed a linear ramp from black to white. But our eyes do not perceive it as such.

This gamma corrected version appears to be the smooth linear gradient we were expecting. Looking at its histogram, we can see that the distribution of its brightness values is not linear but follows a curve that peaks in the midtones.

Note: This may not yet be obvious, but the examples above show that each and every rendering algorithm, even physically based ones, will not appear to produce correct results unless Gamma Correction is applied. There is no way to "fix" the look of a linear rendering adding lights or tweaking colors, because the result of even the most simple calculations is distorted. It's exactly like trying to draw a curved line following a ruler

BurritoIncognito

For the scenes that didn't render right, all I have to do is press the "default" button on the render settings. Then it resets the gamma settings and the renders come out fine. Thank you

Oso3D

Wow, I wasn't even close. Ha.

Ah well, I'll stick to Iray. ;)

 

Sven Dullah

BurritoIncognito said:

For the scenes that didn't render right, all I have to do is press the "default" button on the render settings. Then it resets the gamma settings and the renders come out fine. Thank you

Be aware that, for some reason, the default settings are gamma correction off with gamma 1. This means you will not get the optimal results. This is a remain from the "old school" way of doing it. IMO DAZ should change the defaults to gamma correction on with a gamma of 2.20 which is the correct way of doing things;)

Oso3D said:

Wow, I wasn't even close. Ha.

Ah well, I'll stick to Iray. ;)

 

Hehe, well I don't know how IRay does it, but I'm sure there is a similar function built in?

Richard Haseltine

Sven Dullah said:

Well if I'm not wrong, the renderer internally uses a linear color space, so for that linear render to look correct you need to apply gamma correction to it.

A quote from this article: https://www.vfxwizard.com/tutorials/gamma-correction-for-linear-workflow.html

II. The boring but necessary demonstration of Gamma usefulness

As boring as they may look, the following images demonstrate how our eyes work. Both images are renderings of the same scene. A flat black surface with a white linear gradient starting at the center and growing outward. We expect the rendering to produce a smooth transition from light to darkness, similar to lighting a purely diffuse sphere from the observer's position.

The first image is the straight linear render, while the second one has a 2.2 Gamma correction applied.

This linear image seems to have a contrast peak both in the white center and in the dark outer region. It also looks smaller, while it is of the same size as the other one. Looking at its brightness histogram, we can verify it is indeed a linear ramp from black to white. But our eyes do not perceive it as such.

This gamma corrected version appears to be the smooth linear gradient we were expecting. Looking at its histogram, we can see that the distribution of its brightness values is not linear but follows a curve that peaks in the midtones.

Note: This may not yet be obvious, but the examples above show that each and every rendering algorithm, even physically based ones, will not appear to produce correct results unless Gamma Correction is applied. There is no way to "fix" the look of a linear rendering adding lights or tweaking colors, because the result of even the most simple calculations is distorted. It's exactly like trying to draw a curved line following a ruler

Yes, you need to linearise the images - but that is handled by having gamma Correction on and having the correct gamma set for the image (in the Image Editor dialogue). The Gamma value in render Settings is applied to the final render, it has nothing to do with linearising the inputs. Yes, the final image will usually need gamma correction - but that comes at the end of the process (which the render may well be, so adjust its gamma by all means).I wasn't arguing over linear workflow of final gamma adjustment, I was pointing out that they are separate things.

Sven Dullah

Richard Haseltine said:

Sven Dullah said:

Well if I'm not wrong, the renderer internally uses a linear color space, so for that linear render to look correct you need to apply gamma correction to it.

A quote from this article: https://www.vfxwizard.com/tutorials/gamma-correction-for-linear-workflow.html

II. The boring but necessary demonstration of Gamma usefulness

As boring as they may look, the following images demonstrate how our eyes work. Both images are renderings of the same scene. A flat black surface with a white linear gradient starting at the center and growing outward. We expect the rendering to produce a smooth transition from light to darkness, similar to lighting a purely diffuse sphere from the observer's position.

The first image is the straight linear render, while the second one has a 2.2 Gamma correction applied.

This linear image seems to have a contrast peak both in the white center and in the dark outer region. It also looks smaller, while it is of the same size as the other one. Looking at its brightness histogram, we can verify it is indeed a linear ramp from black to white. But our eyes do not perceive it as such.

This gamma corrected version appears to be the smooth linear gradient we were expecting. Looking at its histogram, we can see that the distribution of its brightness values is not linear but follows a curve that peaks in the midtones.

Note: This may not yet be obvious, but the examples above show that each and every rendering algorithm, even physically based ones, will not appear to produce correct results unless Gamma Correction is applied. There is no way to "fix" the look of a linear rendering adding lights or tweaking colors, because the result of even the most simple calculations is distorted. It's exactly like trying to draw a curved line following a ruler

Yes, you need to linearise the images - but that is handled by having gamma Correction on and having the correct gamma set for the image (in the Image Editor dialogue). The Gamma value in render Settings is applied to the final render, it has nothing to do with linearising the inputs. Yes, the final image will usually need gamma correction - but that comes at the end of the process (which the render may well be, so adjust its gamma by all means).I wasn't arguing over linear workflow of final gamma adjustment, I was pointing out that they are separate things.

Tks for the clarification, much appreciated;)