A bunch of questions Tweet

[hdace]

Hi Juanjo,

I hope you don’t mind answering some questions for us that we keep debating. All our computers are busy rendering or we’d just do some tests to find the answers, but some of them should be in the documentation anyway…

In the Glossy Shader there’s a node input called Normal which takes a Boolean value. Those values would be zero or one, right? A colleague was saying one should be able to enter angle values similar to native LW smoothing, but i was saying that’s not possible. Is this part of the “unbiased” theory?

I haven’t been able to work out what Transmission does in the Diffuse Material shader. There’s no explanation in the documentation.

Octane supports LW Limited Region Borders. I know the following seems obvious, but I just want to be sure: in the render target kernels one chooses “Max Samples” (per pixel - and not “By time”). Since the limited region has fewer pixels than the full image, does this mean that each pixel still gets the same number of samples, and therefore the limited image will render much faster than the full image and at exactly the same quality?


We’re quite confused about the bottom two buttons in the two Emission nodes. One is Cast Illumination and the other is Surface Brightness. These are explained in the new features section of the Daily Build thread, but it’s still confusing.

I understand that if Cast illumination is turned off it’ll disable emission. We use that, for example, with stars in space. We don’t want them to emit light, just to have a constant surface. To do that, is it necessary to also have Surface Brightness turned on? Otherwise they simply become diffuse objects. In fact, doesn’t that mean there’s no point in having an emission node if both options are turned off?

In your explanation of Surface Brightness you say, “…the total emitted power will be dependent on the emitter surface area.” This suggests that it doesn’t just control the brightness of the surface, but also how much light is emitted. That’s the biggest confusion. With it on, making a mesh item bigger allows more light to reflect off nearby objects. With it off, making an item bigger appears to dim nearby objects, even if the total power remains constant. It’s a useful button to have, but it took a long time for me to understand it. Perhaps it should be called “Power Scaling”?

Since Surface Brightness still has an effect if Cast Illumination is off, then it becomes Surface Brightness Scaling. I think…


In a space scene with a spaceship and stars, using the PMC kernel, would adjusting the Ray Epsilon level be useful?

Does “Keep Environment” keep bloom in the alpha channel? I’ve noticed that in the “Main” pass, with alpha turned on, the bloom effect is missing. If one enables the Post Processing in the Beauty Passes tab the resulting file has no alpha channel even if it was enabled and the other files do get an alpha channel. I didn’t enable “Keep Environment”. Can’t test right now, too busy rendering.

Thanks for any “illumination” on these subjects.

—Hal

[atnreg]

Great questions and thoughts, I could add some:
The Scattering node has teh Scale setting. It is type Distance but it has nothing to do with any distance, it obviously is just some kind of scale. For example for a candle on a table the suitable scale is 120m which makes no sense at all. Or if it does, then please explain what that Scale setting means SSS is very complicated thing in general so it would be very important that the settings were as understandable as possible.

I think that at some point the scale control has accidentally switched to distance type as in the manual picture it is still percent value.

Juanjo, please can you fix that control type so that it makes sense and please can you update the manual so that it matches the latest version? The plugin is at point where it could easily be the official version and so the manual could and should be updated. Now in manual there are many things that are way behind even the official version imho (like Scatter node I think). So even though it is of course great to get more new incredible features, it would be important that the documentation was up-to-date

Thank you once again million times for this absolutely amazing plugin and keep up the great work!

Antti

[gordonrobb]

Good questions.

[juanjgon]

In the Glossy Shader there’s a node input called Normal which takes a Boolean value. Those values would be zero or one, right? A colleague was saying one should be able to enter angle values similar to native LW smoothing, but i was saying that’s not possible. Is this part of the “unbiased” theory?

This flag only enable/disable the smoothing effect. In the LightWave plugin you control the smoothing angle using the native "Smoothing" and "Smooth Threshold" parameters available in the LW Surface Editor.

I haven’t been able to work out what Transmission does in the Diffuse Material shader. There’s no explanation in the documentation.

The transmission in the diffuse material controls the "translucency" effect. You can see some samples here:
viewtopic.php?f=5&t=42420&hilit=transmission

Octane supports LW Limited Region Borders. I know the following seems obvious, but I just want to be sure: in the render target kernels one chooses “Max Samples” (per pixel - and not “By time”). Since the limited region has fewer pixels than the full image, does this mean that each pixel still gets the same number of samples, and therefore the limited image will render much faster than the full image and at exactly the same quality?

I am not sure how Octane handle the samples parameter when the active region is enabled, but currently you are going to get roughly the same time with the limited region enabled and disabled, but of course the image with a limited region enabled is going to have less noise than the full image.

We’re quite confused about the bottom two buttons in the two Emission nodes. One is Cast Illumination and the other is Surface Brightness. These are explained in the new features section of the Daily Build thread, but it’s still confusing.

I understand that if Cast illumination is turned off it’ll disable emission. We use that, for example, with stars in space. We don’t want them to emit light, just to have a constant surface. To do that, is it necessary to also have Surface Brightness turned on? Otherwise they simply become diffuse objects. In fact, doesn’t that mean there’s no point in having an emission node if both options are turned off?

In your explanation of Surface Brightness you say, “…the total emitted power will be dependent on the emitter surface area.” This suggests that it doesn’t just control the brightness of the surface, but also how much light is emitted. That’s the biggest confusion. With it on, making a mesh item bigger allows more light to reflect off nearby objects. With it off, making an item bigger appears to dim nearby objects, even if the total power remains constant. It’s a useful button to have, but it took a long time for me to understand it. Perhaps it should be called “Power Scaling”?

Since Surface Brightness still has an effect if Cast Illumination is off, then it becomes Surface Brightness Scaling. I think…

"Cast illumination" disable the light emitted by this emission material. It doesn't illuminate the scene anymore.
"Surface brightness" will cause emitters to keep the surface brightness constant independent of the emitter surface area. You can scale your emitter object and the surface brightness (the color that the camera can see) is now constant. Try it yourself
I will update this information in the docs as soon as possible.

In a space scene with a spaceship and stars, using the PMC kernel, would adjusting the Ray Epsilon level be useful?

Nope, your scene should be defined only in simple precision floating coordinates space. Remember that Octane works with simple precision math. The epsilon value can adjust the rendering artifacts if you work with large or really small scenes, but only inside the simple precision floating math. You can't render a 1 millimeter detail in a 10 km. spaceship.

Does “Keep Environment” keep bloom in the alpha channel? I’ve noticed that in the “Main” pass, with alpha turned on, the bloom effect is missing. If one enables the Post Processing in the Beauty Passes tab the resulting file has no alpha channel even if it was enabled and the other files do get an alpha channel. I didn’t enable “Keep Environment”. Can’t test right now, too busy rendering.

Here I get the bloom effect in the beauty pass with the alpha enabled, can you post an example about this issue?

-Juanjo

[juanjgon]

The Scattering node has teh Scale setting. It is type Distance but it has nothing to do with any distance, it obviously is just some kind of scale. For example for a candle on a table the suitable scale is 120m which makes no sense at all. Or if it does, then please explain what that Scale setting means SSS is very complicated thing in general so it would be very important that the settings were as understandable as possible.

Yes, true. It is not a distance parameter. It is a multiplier parameter.

The absorption texture and the scatter texture is multiplied with this scale parameter. I will change this parameter to a standard floating value for the next release.

-Juanjo

[atnreg]

Thank you again, Juanjo!

[hdace]

Thanks, that does shed a lot of light! I'll test the bloom/alpha issue again and let you know if I still have a problem. Happy New Year!!

[hdace]

Alpha channels can be very useful, but not as Octane is currently configured. I’m not sure if this is a Standalone or plugin issue, but the Post pass is currently not giving us anything we can actually use. What we need is the ability to make subtle changes to the background without having to re-render the foreground.

The Main pass gives us the original foreground items minus the bloom and glare from the post pass in the alpha channel (and the full image in the primary channel). This is how the alpha channel renders whether or not Keep Environment is turned on. Since it’s the Main pass, the alpha channel really should have all foreground elements including the post pass in greyscale.

However, if others disagree and feel the post pass should be kept separate, that’s okay too, as long as the post pass works properly. Unfortunately, it doesn’t. The post pass, whether or not Keep Environment is on, always comes with a completely black alpha channel. There is no data there at all. What it ought to have is a greyscale version of the bloom & glare ONLY. That way it can be used, in conjunction with the main pass, to mask the foreground over a new background in After Effects without any extra masking work.

[hdace]

The current Beta2 of version 2.2 does seem to make the passes node a little more logical, and is helpful. But I still am not seeing the one thing that I am really hoping for: an alpha channel in the Beauty Post Processing option output. If one turns on the Alpha Channel option in the Kernel, the Main Pass and all of the other Beauty option outputs will include an alpha channel. Why not Post Processing? I just don't get it.

At the moment we're making do by using After Effects Modes such as Screen & Add to allow the "glare" from the Post Processing to be seen over the background. This is working but I fear a situation will arrive someday when this won't work. Having a proper alpha channel is a better solution for this workflow.

Thanks, Hal