Background / Environment / Skylighting discussion

[nathanletwory (Nathan 'jesterKing' Letwory)]

Ok, this is a bug in handling the new basic environment that does not have a texture set.

For now you can add a Single Color texture with the color of your choice in the custom skylight environment.

[nathanletwory (Nathan 'jesterKing' Letwory)]

@robinp

Although we disagree on the use of the background for lighting, putting that aside for a moment, surely if an environment is set it should be the environment which is used, not the background. As per the render view.

Yes, that is a bug.

[robinp]

So this is a way to achieve what we want in the short term then. Just make sure an environment is always set and until this bug is fixed, apply a texture to the basic environment to force it to eg white.

edit: not quite because it still changes transparency

[nathanletwory (Nathan 'jesterKing' Letwory)]

Well, a custom skylight environment has to be set if you don’t want skylighting to use the setting of the Background section.

The bug is that with your custom basic environment just the color doesn’t work correctly. For that indeed you have to work around with Single Color texture for until fixed:

RH-61842 Basic environment with only background color set doesn’t work correctly in Skylight

@robinp

edit: not quite because it still changes transparency

Yes, we have opted to show what is in the background through transmissive and transparent surfaces.

Say you have set the solid bg color to white. Now you have a reddish color in the skylight environment. A glass orb would show through it red instead of expected white.

[robinp]

@nathanletwory

Say you have set the solid bg color to white. Now you have a reddish color in the skylight environment. A glass orb would show through it red instead of expected white.

I’m finding the opposite is true. A white environment with a red background results in a red glow.

Edit: maybe the above is confusing because I have transparent background turned on. Here it is with it off:

[D-W (Przemysław Doliwa)]

@nathanletwory

wrt majority - you and @robinp are the first to request this as far as I know

I said I just imagine that due to all other engines.

@nathanletwory

The naive environment implementation from @D-W breaks hard for say a glass where the skylight and/or reflection environment is different from what is in the background. You expect to see what is in the background, not any of the other environments.

@nathanletwory if you would look closely to my screen you would see I try to change only the backdrop - breaking down things below:

@nathanletwory

where the skylight and/or reflection environment is different from what is in the background

Highly expected in product showcase renders for eg.

[nathanletwory (Nathan 'jesterKing' Letwory)]

@robinp

I’m finding the opposite is true. A white environment with a red background results in a red glow

You show a different scenario than what I was talking about.

How it works now:

The background is set to be an environment to illustrate, but if we were to use any other environment to show through the glass bowl you’d get an ultimately weird effect - a small part of a completely different environment from what you expect.

Whatever is in the background section is what is your environment. With nothing set in custom reflection environment this is also used as reflection environment.

If you have skylighting enabled, the setting for what is in background is used for skylighting. Unless you set a different environment.

What I do see though is that the background does appear to contribute somewhat to diffuse bounces. If I recall correctly this is due to how skylight sampling is implemented in Cycles. I’ll log a bug for it ( RH-61843 Background slot environment appears to influence diffuse bounce of rendering )

[nathanletwory (Nathan 'jesterKing' Letwory)]

@D-W

if you would look closely to my screen you would see I try to change only the backdrop - breaking down things below:

This is how it works.

But don’t forget that there is also transparency… A glass over the black background will show the black background through it. A glass over a white background will show white through it. Or whatever you have set in the background section, as I showed.

[robinp]

@nathanletwory

You show a different scenario than what I was talking about.

You were talking about the glow from an object illuminating on another? Eg, as per the magenta background example above?

Still, my example is weird.

I think if you have an environment set it should be that which is visible in reflections and transparency. Isn’t it also weird to have an environment appearing in reflections but not in transparency?

I agree with your note in the you track that it should be a toggle. I can see situations where the user may want either approach.

[nathanletwory (Nathan 'jesterKing' Letwory)]

@robinp

Isn’t it also weird to have an environment appearing in reflections but not in transparency?

Well, the custom reflection environment is for reflections, custom skylight environment is for skylighting, anything else is the ‘regular’ environment.

[D-W (Przemysław Doliwa)]

@nathanletwory

But don’t forget that there is also transparency… A glass over the black background will show the black background through it. A glass over a white background will show white through it. Or whatever you have set in the background section, as I showed.

Mhm, I agree and I thought the translucency effect is due to energy conservation inside not due to the background behind the object - especially that I get that result in cycles where I just swap background color. I might be wrong, maybe this is valid for SSS only in Cycles - anyway, Blender Cycles gives me expected results (red screen) with the same material setup while Cycles wrapped in Rhino Render not.

Due to your example if you use a custom enviro for light and refl there shouldn’t be ANY contribution of backdrop in the image in my opinion.

[nathanletwory (Nathan 'jesterKing' Letwory)]

@D-W

Blender Cycles gives me expected results (red screen) with the same material setup while Cycles wrapped in Rhino Render not.

That is not the same environment setup as Rhino Cycles uses.

[D-W (Przemysław Doliwa)]

@nathanletwory

That is not the same environment setup as Rhino Cycles uses.

I understand. Though weird that everywhere else that’s normal, expected and implemented in such a way. So any possibility to allow it?

[nathanletwory (Nathan 'jesterKing' Letwory)]

@D-W

So any possibility to allow it?

In the future, when GH materials are integrated you’ll be able to do that, sure.

[D-W (Przemysław Doliwa)]

@D-W

the translucency effect is due to energy conservation inside not due to the background behind the object

@nathanletwory am I right on this one or my internal line command failed here ?

[robinp]

@nathanletwory

GH materials

Is there somewhere I can read more about these?

[Philip]

@robinp

But what is the point of having background settings and environment settings if they are kind of the same thing?

I think I have to agree here.

@robinp

Why are there both background and environment settings?

I also think this is perhaps a bit confusing…

Philip