Trouble with image sampler and GI. Specifically when using lampshades

[plewallen]

I am having a terrible time trying to get smooth overall lighting in my scene as shown in the first three attachments. As you can see I have a fair amount of geometric detail along with large flat surfaces in my scenes with a lot of glossy reflections in the stainless steel that are also very blurry. In the scene which is now giving me trouble I have lights which have lampshades on them. More specifically spotlights with an opaque finish which is smooth and reflective. There are approximately 50 lights in this scene and I started by using the same exact overall settings for the lights materials and global illumination settings I used in the images which are posted first. Here is a picture of the scene which I am having issues with.



Here are the settings which I have used and failed with

Irradiance Map for the primary bounces and Light Cache for the secondary illumination. The last image shows the overall render settings for the scene.

The only way I was able to get the splotchyness to go down was to turn up the HSph sub division setting in the Irradiance Map settings up to 500 and leave the rest of the settings the same. The lights int eh scene are at 16 Sub Divisions and the reflection settings for the materials are also set to 24 or 32 sub divisions. Changing these to any setting from 8 to 1000 seemed to make very little if no difference.

I have read as many times as I can stand the following tutorials and have only been able to see a change based on the last solution I showed.
http://www.interstation3d.com/tutori...yfing_dmc.html

I would simply like some light shed on the issue and some guidance. I have also tried the settings outline in this thread and I was unable to see them affect this scene of mine.
http://www.chaosgroup.com/forums/vbu...irradiance+map

[3DMK]

My Guess is that your lights are actually inside the Spot-light fixture???
If so then Vray is struggling to get a clean solution do to the fact that for a GI ray to reach the light is has to be refracted through the Spotlight Glass.
Try rendering it with the lights just outside the Spotlight glass...you will get a much cleaner solution ...much quicker...with less subdivisions.
Use a self-illuminated material for the spotlight glass if needed

Hope this helps

[svetlozar.draganov]

I have been in a very similar situation and the solution was to get out the lights of light-fixture.
When the light-source is covered with the fixture it is very difficult for GI to reach it - and the settings that usually generate very clean result and good quality in this case create very splotchy result - which can only be fixed with very very very high GI settings.

[plewallen]

Gentlemen,
Thank you both for your timely responses. First to clarify the conditions of the scene in question. Yes the light sources are "inside" the light housings of the spotlights. Yes these spotlights would be the only light sources in this particular scene. Here is a wire frame close up of how I modeled these lights. Also an update of the global illumination settings being used. And yes having the HSph. subdivisions this high is killing my render times. As in 48 hour render times on a single quadcore machine. A Core i7-3770 to be exact.



3DMK, and svetlozar_draganov, both of your responses helped immensely. It is always nice to confirm that other people have had the same issue and come to the same conclusion on how to resolve it. Although it was not the answer I ultimately wanted to hear it does follow with the technique I used in the other scenes to overcome the issue. It is a bumber that this is the case as I have so many instances where I want to light a scene with a lamp with a shade or minimal global lights. I guess I will need to get my firm to step up and buy some real render servers.

So in the case where I have to cut down on the render times I will use an illuminated mesh as a plug at the end of the light and then have that be the light sources with a vraymaterial light. I say disappointed as I would have liked to have the control of the shape of the light cone by the geometry surrounding it. I suppose one can't have everything. Maybe Pixar has a solution in renderman. I'm sure it is an inexpensive solution also. Again thanks for the help.

Regards,

[3DMK]

Gentlemen,


So in the case where I have to cut down on the render times I will use an illuminated mesh as a plug at the end of the light and then have that be the light sources with a vraymaterial light.

Regards,

I would suggest keeping your lights & placing them outside the lamp.......
Using a mesh with vray Light material applied is also problematic regarding getting a clean & quick GI solution.
To control the light shape you could simply use a Vray photometric.
Cheers
Jamie

[plewallen]

3DMK (Jamie),
After many bouts with highly attuned stubbornnes I finally see what you mean about using IES lights. I managed to not make the connection that the lighting manufacturers provide these files. So now I have a fairly similar spotlight ies file with another bulb illuminating only the inside of the housing along with the proper shape of the light cone. I will post the finished work in a couple of days. Again thanks for the advice.

Cheers,

[svetlozar.draganov]

It would be nice to see the final result - it would also be very helpful if you are able to share IES profile that you are using to resolve this issue.
I am sure that a lot of people will be very thankful to you.

[plewallen]

Well I am happy to help. This forum has been very useful. Here is the final result. After a total redesign of the client. One more qualification, was I was actually laid off before the image was finished and had to get the company to bring me back in on contract to finish it. This cost me another day and a half of time, not to mention the weekend. So I was very rushed at the end. That being said I am very pleased with the result and the IES methodology proposed in this thread.





" It would be nice to see the final result - it would also be very helpful if you are able to share IES profile that you are using to resolve this issue.
I am sure that a lot of people will be very thankful to you. "

Svetlozar Draganov

Svetlozar,
On your last question did you want me to post the ies files or just link to them? Well I can explain how I found them because when I started this scene I had never used IES files before and frankly thought they were a little black magic. And had no idea where to get them. I had the client send me specific cutsheets of the light fixtures. I would model the light fixtures (obviously I suppose), and on the manufacturer website would find their specific IES files. If they did not have them I used a similar product IES light to get what looked to my eye as a respectable light cone for the distribution. Then I would just tweak the intensity of the lights until the overall lighting was acceptable.
I would be more specfic but most of my information was left at my old place of work. But I think the searching for specific IES files for whatever manufacturer you have is ideal. There was one website I found of a guy who had free IES profiles which were being billed as generic. These could be very useful to use for a more "free hand" light painting or for place holders until the light fixture manufacturers have been identified.
A place where I did not use the IES files was for the wall washer lights on the back wall. I used a basic Vray plane light. I was having difficulty orienting the IES light to match the orientation of the wall washer. I tried the regular rotation and the rotation in the IES properties but it was just not working.
I used 3DMK's method exactly which is a small light inside of the housing on very low, such as .05 watts or .1 watt, whatever works, and then the appropriate IES light at the very limit of the light fixture.
I hope this explanation helps. If there is any more specific clarification about this scene please don't hesitate to let me know.

Phil

[svetlozar.draganov]

Hello - thank you very much for the final render.
You can share link to manufacturer website - it would help a lot to the people with the same issue.