Emission incorrectly applied

[Noname]

When importing either emission or emission color is set incorrectly.

All materials do have:

• emission strength of 1
• emission color - light grey

Thanks in advance.
Best regards

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EDIT:

I do see that there is an option for emission in Settings, disabling it (as expected) correct importing issue, but IMHO that’s not proper solution ?

EDIT2:

It appears that this happens only on this asset (as far as I tested): https://www.daz3d.com/creative-office-space so maybe asset issue.

[Thomas Larsson]

Is there any emission in DS?

I often turn off emission to improve render quality. Many daz environments are lit by many small objects like lightbulbs which have emission turned on. This may be physically correct, but it makes it hard for cycles and results in grainy images.

[Noname]

Thank You for the reply.

I was using this asset before and didn’t noticed this, but I did changed since material import options from BSDF to Principled.
When importing as Principled emmission is applied when using BSDF it’s ok.

Here is screen-shoot from Daz material panel for two materials lights and wall:

For the walls material there is emission temp set to 0 and luminance set to 10 - I don’t know what’s relationship between Daz materials and Blender emission so maybe that’s bug (i.e. value from Emission Temperature should be taken into account and color in this case would be ignored - with is correctly imported into Blender)?

Anyway when using BSDF it’s all OK so I’m suspecting that this is working as intended and issue is just that we can’t accurately move materials between iRay and Blender.

[engetudouiti]

I suppose we can mimic it as cycles shader, but basically cycles not support light Temprature as default. so I do not think add on import light work as same as DS for emiiter geometry which attached daz iray Uber Emisson. (or attach MDL Emission shader)

There are a few article user try to include it in cycles light shader. But I do not know it is perfecty correct or not.. I usually do not like just guess and mimic it with test some scene when the enhancement need to get physically correct render.. if it is enhanced as real math and physics I apreciate , add on will take count tempreture for cycles custom emission shader.

https://blender.stackexchange.com/questions/180507/simulating-a-40w-light-bulb

[Alessandro Padovani]

Unfortunately the article on the emission implementation is lost in the old tracker. But I’m pretty sure we didn’t take into account the light temperature, if this is the issue. The solution pointed by Engetudouiti works fine here. We can use a black body with the light temperature that is then to be multiplied with the emission color itself.

edit. important. There’s one caveat that temperature zero in iray is not the same as zero in blender. It seems iray means 6500 for zero. So when iray is zero we use 6500 in blender. Other than that it seems to work fine.

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As for the watt conversion we used 15 lumens per watt that’s what blender 2.7 did at the time. It seems it works fine for 2.92 too.

Test scene attached emission.duf. Below an example with the black body, first iray then cycles.

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[Alessandro Padovani]

test for the light temperature

[Thomas Larsson]

Implemented in last commit

[engetudouiti]

I think the blackbody part correctly show the emitter color. (the daz auto 0 = default 6500 setting is simply annoying and nonsense I think, vendor should set real kelvin without use default 0 (though ds auto set it as white)

At same time, I hope to know Thomas setting, in daz tone mapping and blender Color management

I can manage world for scene which need not any blender light (ds light node) but use geometry emitter. and can hide un-necessary blender lights.

So tone mapping setting is only matter.

eg when I import scene for cave with geometry light source only,, how Thomas set ds and blender tone mapping?

(then can check the emission shader is correctly represent light effect) It is important to use Global setting import options about light .

I usually keep it as blender and daz default (tone mapping on)

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[Alessandro Padovani]

Commit 2cc1a9f works fine here. We may mark as resolved.

Engetudouiti, as for tone mapping actually we don’t import it. It is quite hard to map the daz tone mapping into the blender color management. We may need to use the curves to do it.

The big difference is that daz studio uses values for burn highlights and crash blacks, these two values essentially define the linear to srgb curve to be applied for color management.

While in blender we get presets with the trasform and look options.

I did some tests a while ago see #22. Personally I believe it is not possible to correctly import the daz tone mapping. Then definitely you may want to open another discussion for this if you are interested since it’s a complex matter that deserves its own discussion. Or I may reopen my old one for you.

[engetudouiti]

No I do not request we need to import daz tone mapping (though it is not bad ) and do not talk detaie the difference etc. I simply ask The real setting of Thomas when he test those enhancement for env or light or mat shader. To test easy.

eg Thomas ttest with Tone mapping on, or OFF. and when import, set blender color manage ment default etc. I only need to know the Daz Tone mapping setting and blender Color manage ment setting of The add on author do.

[Noname]

Temp is imported in nodes for me as well, so works fine.

Closing this one as this issue is resolved.

[Alessandro Padovani]

@engetudouiti You may export a raw image. But the raw image will depend on the light transport equation, light source model, and material models used by the render engine. That are not the same in iray and cycles since they are very different to the core. That is, the fact that two engines are both “pbr” doesn’t mean that they use the same math models. If this is what you’re asking for.

And again to talk about these things you may want to open a separate discussion since this is a complex matter. Then personally I don’t know how much I can help. I know something but I’m not an expert on rendering engines implementation.

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