Arnold Q&A

[origin]

-how do you do shadow/reflection catching material?
-it seems that specular and reflection values are added together so there is no energy conservation?

[xsisupport]

-how do you do shadow/reflection catching material?

For shadows, you can use the Shadow shader (sib_illum_shadowmaterial). MtoA has a shadowcatcher shader, so you can use that too (if you put the mtoa shader dll in the shader search path). Some customers write their own.

-it seems that specular and reflection values are added together so there is no energy conservation?

Generally you shouldn't use both at the same time. Use either glossy (specular) or mirror (reflection).
From the FAQ

Why does the standard shader compute reflections twice?
The standard shader can compute both sharp and glossy reflections.

Sharp reflections are controled by the Kr and Kr_color parameters. This type of reflection uses one ray per shader evaluation, with a depth limited by the GI_reflection_depth global option.

Glossy reflections are controled by the Ks, Ks_color, specular_brdf, specular_roughness and specular_anisotropy parameters. This type of reflection uses GI_glossy_samples to determine how many rays to trace per shader evaluation, and the depth is limited by the GI_glossy_depth global option. Note that using a specular_roughness of 0 will also give you a sharp reflection, but doing this is slower than using the pure mirror reflection code.

These two types of reflection can coexist and have independent Fresnel controls. They are simply added together with the other components of the standard shader, without taking into account any energy conservation. We will probably end up unifying both types of reflections in the future.

[origin]

So far im loving it. One slider to boost quality instead of 2 windows full of options.
But Im not sure if its good choice for freelance due to lack of interpolated GI solutions.
btw...vray 3.0 rendernodes no more free (250euro)

[Dwindleflip]

Keep in mind its a lot more than just 1 slider. The 1 slider you're referring to is probably the AA slider but really the diffuse samples, glossy specular samples, refraction samples and individual light samples will often need to be tinkered with to find a good balance for render times. Specular fireflies can be a real pain in the ass too.

[origin]

Yeah, but comparing to vray dmc...its...easy to setup ;)
I might be wrong but I see camera AA acts as multipler for rest of AAs.
So best strategy for noise/rendertime ratio is to lookup all render channels to see which one needs more samples?
Too bad xsi VFB is such crap

My other thoughts
- gamma correction should be set to 2.2 for texture/light/shaders by default, now its on 1.0. Anyone still not using LWF/exr workflow?
- area lights should have normalize off by default

[xsisupport]

...
I might be wrong but I see camera AA acts as multipler for rest of AAs.

That's right.
https://support.solidangle.com/display/ ... ridofnoise
How to get rid of noise
Computationally, the efficient way to get rid of noise is to go from the bottom up (going from the particular to the general). We would increase the sampling of individual lights first, then the GI and glossy samples. Finally, the AA samples, which acts as a global multiplier of the whole sampling process. However, the only way to improve the quality and reduce the noise of motion blur and depth of field is to increase the AA samples. In this case, this AA increase allows you to decrease the other sampling rates (GI/glossy/light) to compensate. To sum up, you will get almost the same render time with AA=1 and GI=9 than with AA=9 and GI=1, but at AA=9 you will have much better motion blur and depth of field quality. More information can be found here and a workflow here.

And on the subject of AA and noise: https://support.solidangle.com/display/ ... ving+Noise

[Dwindleflip]

Actually, I leave gamma at 1 for shaders and lights. I set viewport to 2.2 because softimages viewport gamma correction doesnt convert the physical sky properly for some reason at high values, the sun will do odd things. As long as your textures are profiled, arnold/softimage will read them as 2.2 or linear respectively. I leave shaders at 1 because i use the softimage color correction for color thumbnails. I really wish softimage viewports were gamma corrected in realtime shading mode. HQ mode is terribly slow so i never use it

[Rork]

Gamma settings depend on your workflow and SI version, and not using LWF is a sin ;-P

By default the gamma settings in Arnold are set to 1,0.
A lot of people leave the default SI (2012/2013) settings alone, and set Arnold to use a 2,2 gamma.
But AFAIK SI 2014 (not using it atm) changed some stuff in the way gamma is handled, so some people reverted back to the 'old ways' and set gamma in the SI settings. Leaving the default Arnold gamma to 1,0.

These topics might be better off with a separate thread.
I suggest starting with a 'Arnold' tag at the front, so people know what renderer you're chatting about.
With the site online now, I can only see more topics pop up here on Arnold rendering soon ;-)

[owei]

Hey!

As Arnold finally is available officially, questions about Worklfow, setting etc can be posed here. I´ll move certain posts from the "Arnold released" thread here.

Cheers,
oli

[origin]

Is it possible to rendermap with A.? Couldn't find it in docs / rendermap's regenerate maps doesn't work

[mattmos]

There's a kettle bake shader around somewhere. Edit:

https://bitbucket.org/Kettle/kettle_ube ... ettle_Bake

[origin]

Thanks! but...can anybody confirm its working with sitoa 3.01? kettle shader.dll is all red in plugin manager

[xsisupport]

Thanks! but...can anybody confirm its working with sitoa 3.01? kettle shader.dll is all red in plugin manager

SItoA 3.0.x uses a version of Arnold that requires a recompile of all shader and procedurals. Kettle hasn't been recompiled yet (I don't see a new version on the downloads page).

[Dwindleflip]

The physical sky shader doesnt allow you to plug maps into any of its values which is odd so it seems impossible to make any kind of faked clouds layered into it that are effected in the haze of the shader. Whats the best way to create clouds and environment using the physical sky shader?

[alanf]

Is it possible to rendermap with A.? Couldn't find it in docs / rendermap's regenerate maps doesn't work

Not presently supported, last I looked. (To get rendermaps to render at all you'll have to temporarily switch your Scene Renderer to mentalray btw.)

[sant0s]

hey,
just tried to test render on rebus farm - but it always gives error message that the path to images is wrong and stops rendering.
so I guess, I have to check/uncheck something and maybe change the environment for textures?