Global Illumination 2016

[halfstone]

I have set up a standard Cornell Box with a white Lambert material on the top, back and bottom faces; a red Lambert on the left and a blue Lambert on the right.  I am using a Maya area light facing downward as my light source, with "Use Light Shape" turned on and "Visible" checked.  I have used this setup in many past versions of Maya, including 2014 and 2015.

I read Ryan Harvey's post about setting the preferences to "Use Legacy Render Settings" when using GI or FG, and have done this.  

I have set Global Illumination to "on" and left the settings at the defaults; I have set "Emit Photons" on my light to "on", and left the Color, Intensity, and Exponent at their defaults. 

The photon result does not render unless I have intensity on the light. The render time is substantially increased, however, so something is being calculated. 

In previous versions, I was able to turn the light intensity to zero, to evaluate and adjust only the photons, and to then balance the indirect illumination against the direct. 

Further, when using diagnostics, I cannot generate a photon map to diagnose. 

I have tested this with Maya 2015 and 2016 with the exact same settings, and it does not work in 2016.

If I turn the light intensity to a non-zero value, the photons do appear to have the desired effect, but there does not seem to be much control or diagnostic capability.

Is this a bug, or is there a new setting that I am unaware of?  The "help" documentation is not meaningful at this time because it refers to a non-working setup; per Ryan Harvey's suggestion I am using the legacy settings. 

[santd]

Hello,

Thank you for posting to the Area Forums.

I tested this on my end in Maya 2016 and was able to get it to work once I enabled the Legacy Rendering features. One thing I noticed is that I had to restart Maya 2016 in order for me to see the legacy Features tab in the Render Settings. Maybe after a restart you will see the Features tab where you can enable GI, Caustics, FG, etc.

I hope that information is helpful.

Cheers,

[halfstone]

This appears to have been an issue with SP1; although I'm pretty certain that I had SP1 for both Maya and mental ray installed when the problem began.

I re-installed the mental ray service pack and am able to get this to work.  However, there still seem to be a lot of issues.

When using the Legacy Render Settings, I am unable to save out a photon map - if I select "rebuild photon map" and put in a name, no new photon map is created; I have tried this by re-setting my project and by putting in an absolute path to the ~\project\renderData\mentalray\photonMap directory, but I cannot save out a map.

Further, adjusting the number of Global Illum Photons has no effect on the scene - I have gone from the default setting as low as 50 and as high as 20,000, but get no change whatsoever - and "Rebuild" is set to "on" in all cases.

Finally, I decided to start from scratch and turn off Global Illumination and turn off "Emit Photons" in the light attributes, but my input does not effect the generation of photons.  I have made sure that I'm not re-using the default pmap, but I still get GI in my render.  I've gone as far as to delete the default.pmap from the Render Settings folder, but once they are turned on they are on for good. 

In order to turn them off, I have to go BACK to the prefs and return to the new (2016) settings, then exit Maya, re-start Maya, and turn off the Indirect Diffuse (GI) mode. 

This produces a render without GI. 

However -

When I turn this back ON, I will get a GI render EVEN IF my light is set to NOT emit photons!  If I turn the photons back on in the light, I have no control over the color, the intensity, the exponent or the number of photons. (I have apparent control, i.e., the sliders and dialogue boxes are active, but nothing I do changes anything.  The render is completely out of my control.

This is CLEARLY broken. 

[ddankhazi]

Your right. It's like you wrote above.
Maybe the new Global Importance Sampling feature cause this.
"Oh your not emitting light, you are nothing, you are not important to me, so I ignore your photon emission as well."
🙂
Maybe not. I hope they fix it soon.
Cheers

[santd]

Hello,

Thank you for that information. I have gone ahead and reported this to our development team. They will be taking a further look into the issue.

Cheers,

[ddankhazi]

For the record.
The solution is so simple it hurts.
Turn off Emit Diffuse and Emit Specular for the actual photon emitting light.
It is the same effect as in earlier mental ray versions when you turn off the Illuminates by Default option.
Probably it is not a bug just a different way.

p. s.:
As a result of further studies in subject:
the new mental ray is really great.

[halfstone]

Thanks.  It hurts, alright. 

How did you come to this solution?  Trial and error?  

I'm still a little unclear as to how to control these photons.  In order to enable the "number of photons", "intensity", and "exponent" features, you have to go into the Legacy options and turn GI on - but this does nothing at all.  

The decay of the photons seems to be controlled by the decay of the light, which I suppose is reasonable - you can leave the intensity of the light alone.  But what about quality?  

Also, is there a way to use FG and GI together?  In 2015 and before,  they were separate check-boxes and you could use some pretty low photon settings but still get good quality with FG, here it is an either/or selection, not both.  I've opened the "Legacy Option" and enabled both, but the FG doesn't work unless it is enabled above (again - you have to choose between options). 

Finally (at least for this post), given this new system - whether it's a bug or a feature - there seems to be no way to separate or balance the intensity of the direct illumination with the photons.  

I'd love to see some documentation of this workflow, but the Maya help files are not updated or relevant.  

[ddankhazi]

Hi,

It cost some time but I figured it out pretty much everything what I want to know about the new mental ray.
I read the elemental ray blog (https://elementalray.wordpress.com/) and the mental ray documentation. 🙂

A "short" list (order in relevance):

–– Lighting quality: Globally change how mental ray compute lights. (Pup up this for 30 creates a smooth render usually.)
This control every Area Light sampling in the scene (by default).
You do not need to change every area light "High Samples" attributes anymore (except if you using portal lights!)!!!!!
You can turn this feature off by choosing the Advanced Settings, Advanced Light Sampling, Light IS - Off (this is the new Light Importance Sampling algorithm).

–– Indirect Diffuse (GI) Mode: On (GI Prototype = GI NEXT but it is not finished (some features are missing but really good stuff) so they call it Prototype :))
This is a totally new Brute Force GI system (works like Arnold, iray, Maxwell etc.).
If you enable this you do not need Finalgather or the old Global Illumination (photon tracing) system.
Use the Indirect Diffuse Quality slider to improve the image quality. (Well above 1).

–– If you choose Finalgather instead you definitely want to check the Show Advanced Settings box.
In this case don't bother the Indirect Diffuse Quality slider. Scroll down to Legacy Options -> Final Gathering, and use it as usually.

–– You can use of course the "classic" Global Illumination Photon Tracing System alone (again this has nothing to do with the new GI Prototype system) or use with Finalgather.
If you want to see only the photons turn off any GI system.
Indirect Diffuse (GI) Mode: Off.
Turn on the Global Illumination (under the Legacy Options).
Emit photons via lights. Set the attributes as you need. Turn off Emit Diffuse and Emit Specular. Render. Now you happy. This way you fine tuning as earlier (Maya 2015 and before).

That's it. For now.
Cheers, D

p. s.:
Here some test image mainly caustics tests. (Using the old Global Illumination technique with photons, caustics photons combined with Finagather.)