Need clarification: Mental Ray legacy MIB_LIGHT_SPOT

[hilaire.gagne]

Hi Folks,

According to the Maya 2014 documentation, the workflow for implementing a Spotlight /w Fog for render using Mental Ray requires the use of a Legacy MIB_LIGHT_SPOT:

http://download.autodesk.com/global/docs/maya2014/en_us/index.html?url=files/mrfMS_Create_light_fog_...

Hopefully a seasoned Maya veteran can help set me straight:

Why was MIB_LIGHT_SPOT moved to the Legacy node in Hypershade, is there a new method of implementing fog on a Spotlight that I should be using?

Is the above workflow still applicable when using Unified Sampling; the documentation seems to imply that the Legacy Node items are intended for pre-2014 scenes using the pre-Unified Sampling render method and that Legacy Node items should be used anymore?

Advanced thanks,

[hilaire.gagne]

Alright ....

Implementing the workflow as noted in the Maya 2014 documentation (see link previous post) does not seem to work when rendering via Unified Sampling.

When I connect the MIB_LIGHT_SPOT to the Mental Ray > Custom Shaders > Light Shader slot of the Spotlight, the universe as we know it ceases to function.

I was able to achieve results in my test scene by doing the following:

- Physical Sun & Sky

- Camera Environment Shader = mia_physicalsky

- Camera Lens Shader = mia_exposure_photographic

- Set the Physical Sun & Sky Multiplier = 1 (simulate night)

- Spotlight with the following settings:

  Intensity = 5000000.000 (to compensate for PS&S and Exposure)

  Decay Rate = Quadratic

  Light Effects = LightFog node

  Fog Spread = 2

  Fog Intensity = 2

  Enable Decay Regions

  Set Region 1 & 2 = 0,0

  Set Region 3 = 1,120

- Adjust the LightFog node:

  Color = PINK (so I can see the fog)

  Density = .001

  Color Base Transparency = Selected

  Fast Drop Off = Unselected

@AUTODESK:

Folks, I sincerely appreciate ALL of the efforts that goes into the development of products such as Maya and having been in the technology industry for close to three decades, I understand the complexity involved in applications such as Maya.

That said, either you need to increase the QA team three-fold to regression test the application properly or you need to increase the Technical Writing team substantially so as to update ALL of the documentation accordingly.

I am not aware of how many Autodesk Sales/Development/QA/Writers frequent the AREA forums, but it doesn't seem like there are many.  Often times, threads go unanswered for extended periods of time if at all. 

Respectfully yours,

[santd]

Hello hilaire.gagne,

Thank you for your post on the forums. I wanted to let you know that I have tested the process explained in the Maya documentation that you provided. I tested in the Service Pack 1 for the Maya 2014 Extension and the render worked just fine using the Unified Sampling Mode in mental ray.

Are you using the latest version of Maya 2014? If you don't have the latest service pack for Maya 2014, I would recommend installing it from the following link or installing the Maya 2014 Extenstion Service Pack 1 from the Subscription Center:

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=22443097&linkID=9242259

It's possible this was an issue in the early realease of Maya 2014 but was later relsoved so I would definitely recommend installing the Maya update. I hope this information is helpful.

Cheers,

[hilaire.gagne]

---

@santd wrote:

Hello hilaire.gagne,

Thank you for your post on the forums. I wanted to let you know that I have tested the process explained in the Maya documentation that you provided. I tested in the Service Pack 1 for the Maya 2014 Extension and the render worked just fine using the Unified Sampling Mode in mental ray.

Are you using the latest version of Maya 2014? If you don't have the latest service pack for Maya 2014, I would recommend installing it from the following link or installing the Maya 2014 Extenstion Service Pack 1 from the Subscription Center:

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=22443097&linkID=9242259

It's possible this was an issue in the early realease of Maya 2014 but was later relsoved so I would definitely recommend installing the Maya update. I hope this information is helpful.

Cheers,

---

Hi David,

Appreciate the reply; I am using Maya 2014 SP2 (*not* EXTension). 

I tried it again today and there's absolutely no way to get it working.  As soon as I connect the MIB_LIGHT_SPOT, the Spotlight ceases to function.  I was able to achieve the results I required using the steps I noted in my previous post ... obviously with some adjustments to the values once I had it working.

I'll look to update to Maya 2014 SP3 or Maya 2014 EXT SP1 once this project is completed; but at the moment, I can't take the risk of having to possibly rework aspects of my project as a result of  Service Pack changes/updates.

Cheers,

[hilaire.gagne]

When I render the scene via Mental Ray (incl. Physical Sun & Sky and Final Gathering), the area that coincides with the Spotlight Cone Angle is rendering darker in the direction the where the Spotlight is pointing ... even though the Spotlight Intensity is set to 0.

When I turned off the system late last night, was not experiencing this issue; after power-up this morning, no success rendering.  It's looking like I'm going to have to try the SP3 update after all to see if it will resolve the issue.

I'll try the MIB_LIGHT_SPOT afterwards to confirm if it's working now or if the same problem exists.

Cheers.

[hilaire.gagne]

---

@santd wrote:

... I wanted to let you know that I have tested the process explained in the Maya documentation that you provided. I tested in the Service Pack 1 for the Maya 2014 Extension and the render worked just fine using the Unified Sampling Mode in mental ray ...

---

Hi David,

Updated to Maya 2014 SP3; at least the rendering issues I was experiencing appear to be resolved.

I removed all of the Spotlights, ConeShapes, LightFog, etc. via Hypershade, saved the project, restarted Maya and recreated the Spotlights.  The issue with the MIB_SPOT_LIGHT are still present; since you were able to get it working, it has to be something in my scene in the way I'm implementing the Spotlight - I'm at a loss as to what it could be.

As an aside, I'm also noticing that enabling the Fast Dropoff option in LightFog causes the problem I described earlier today ... in that the area in front of the Spotlight (same size as cone) appears darker in the render.

Cheers,

[hilaire.gagne]

Did some more experimenting since my last post and it most certainly has something to do with how I'm implementing the Spotlights and LightFog.

The slightly darker area in the area in front of the Spotlight corresponds to what I'm seeing in the Alpha Channel as a gradation of dark to bright ... which I assume is the fog generated from the LightFog node settings.

... haven't quite figured out what exactly what that means; at least I have some info I can try to look up for reading/researching purposes.

Cheers,

[santd]

Hello,

I have been running further tests and I think I am seeing the issue that you are experiencing. It seems to me that it is caused by the sky or the shadow of the fog. I have created the following video showing The results I am getting:

 https://chronicle.autodesk.com/Main/Details/32588427-6dbd-4517-9c72-289506dcee20

[hilaire.gagne]

---

@santd wrote:

Hello,

I have been running further tests and I think I am seeing the issue that you are experiencing. It seems to me that it is caused by the sky or the shadow of the fog. I have created the following video showing The results I am getting ...

---

Hi David,

Very similar results without the MIB_LIGHT_SPOT.  As soon as I connect the MIB light, all I get is a dark grey semi-transparent shade in the direction of the spot.

If you're interested in seeing the scene file, send me a PM with an email address and/or upload location if you have one.  The entire directory is <40MB.

Cheers,