Strange transparent dots in Iray

gaiago57

Hi, 

since that last update of DS, I have strange little transparent dots in my Iray renders. Most of the time it's around the eyes or the fingers, but sometimes it can also appear around other object : 

I really don't understand why I have those glitches. Has anyone here already had this problem ?

Tobor

Probably firelies. Make sure the firefly filter is on. Sometimes it can get set to off (using someone else's render preset, actually turning it off, etc.)

Fireflies tend to resolve out by the end of the render. They can be worse in highly specular and/or bright areas of the render, and when combining shaders that introduce lots of internal reflections. This is most problematic in eyes, which consist of multiple geometries sandwiched right together. For best results, only the outer-most shader should be glossy or reflective. All the inner ones should be matte, and not reflect at all (or very little).

Tobor

I also want to suggest oyu look at the pixel filter setting in the render settings. Looks like it might be dialed up even higher than the default, which is Gaussian with a pixel radius radius of 1.5. For sharper images, set the radius to .5 or 1. You can add back any gaussian blur in a photo editing program, if you need to (sometimes you do need to, to avoid pixelation or moire effects).

marble

There was a thread with similar problems due to the new version of IRay and the new dual-lobe thingy.

https://www.daz3d.com/forums/discussion/176756/script-apply-dual-lobe-features-to-pre-lobe-g3-skins/p1

gaiago57

Tobor said:

Probably firelies. Make sure the firefly filter is on. Sometimes it can get set to off (using someone else's render preset, actually turning it off, etc.)

Fireflies tend to resolve out by the end of the render. They can be worse in highly specular and/or bright areas of the render, and when combining shaders that introduce lots of internal reflections. This is most problematic in eyes, which consist of multiple geometries sandwiched right together. For best results, only the outer-most shader should be glossy or reflective. All the inner ones should be matte, and not reflect at all (or very little).

Thanks but the firefly filter is already on and I reduced the pixel filter to 0.5 and I still have those spots.

Fishtales

Try setting the Firefly Filter to 100.

gaiago57

Fishtales said:

Try setting the Firefly Filter to 100.

I can only switch between on and off :

Tobor

I amlikewise unaware of a setting for the firefly filter beyond just turning it on or off.

Be aware that this filter does most of its work as the render is finishing. If/when fireflies are an issue in the scene you should wait for it to finish, or at least mosty finished.

Fireflies are generally caused by these things:

1. Excessive internal reflections, such as the eyes. I mentioned this before. It can be hard to eliminate these completely.

2. Excessive highlights. You can try adjusting the lights and light positions. Chrome and brightly shiny materials may produce this.

3. Absolute white in shader colors. Pure white seldom exists in nature. Try a grayer tone.

4. Re-hint the rendering engine by manually adjusting the nominal luminance control (it's at the top of the screen you posted).

There are a couple of Iray blog posts related to this that might help:

http://blog.irayrender.com/post/87877693033/compositing-with-linear-image-output-vs-fireflies
http://irayrender.com/fileadmin/filemount/editor/PDF/iray_Performance_Tips_100511.pdf

Lastly, the fact that these seem to have appeared at the same time as the update suggests there's been a change in Iray and/or D|S that is affecting your renders. I'd recommend sending a support ticket to Daz with before/after images (if you have them), in case it's a new bug.

 

Fishtales

To clarify try setting the Nominal Luminance to 100.

gaiago57

Tobor said:

I amlikewise unaware of a setting for the firefly filter beyond just turning it on or off.

Be aware that this filter does most of its work as the render is finishing. If/when fireflies are an issue in the scene you should wait for it to finish, or at least mosty finished.

Fireflies are generally caused by these things:

1. Excessive internal reflections, such as the eyes. I mentioned this before. It can be hard to eliminate these completely.

2. Excessive highlights. You can try adjusting the lights and light positions. Chrome and brightly shiny materials may produce this.

3. Absolute white in shader colors. Pure white seldom exists in nature. Try a grayer tone.

4. Re-hint the rendering engine by manually adjusting the nominal luminance control (it's at the top of the screen you posted).

There are a couple of Iray blog posts related to this that might help:

http://blog.irayrender.com/post/87877693033/compositing-with-linear-image-output-vs-fireflies
http://irayrender.com/fileadmin/filemount/editor/PDF/iray_Performance_Tips_100511.pdf

Lastly, the fact that these seem to have appeared at the same time as the update suggests there's been a change in Iray and/or D|S that is affecting your renders. I'd recommend sending a support ticket to Daz with before/after images (if you have them), in case it's a new bug.

 

Thanks, I will do some tests to see if I can reduce these "spots", and I think I will send a ticket to Daz.

Tobor

In the meantime I'd follow up with Sandy's advice of messing with the Nominal Luminance. The exact value to use depends on the scene elements, but it's worth a shot.

The luminance value is deried by Iray's tone mapper, which doesn't always do a good job of calculated all the necessary values. You also have the option of manually setting the nominal luminance, which is something you'll pretty much need to do if you ever render with the tone mapper off (recommended if you render to 32-bit canvasses).

 

Ongoing Moment

Having Dual Lobe and Glossy on at the same time sometime creates those random fireflies.