Hey Guys,

Does Mantra have Photometric Light Shading like Mental Ray does?

Cheers,
Nate Nesler

MatrixNAN
Does Mantra have Photometric Light Shading like Mental Ray does?

Hey Nate,

Could you explain exactly what they mean by that phrase for us non Mental ray users ?

Thanks.

Hey Guys,

Ok well you can input the light profile code from the light manufacture and mentral ray will reproduce that lighting to that particular light exactly. Its very useful for Visual Architecture or realistic lighting and such for reproducing exactly way a particular light looks and acts in reality. It was orginally introduced for true Radiosity.

Cheers,
Nate Nesler

Ah I remember Raydiosity and the dense spider-like polygonal surfaces it created and the days that it took to compute. Lightscape was the company that wrote software that used raydiosity to solve it's GI. Didn't AutoDesk aquire them 8 to 10 years ago? I also remember being able to define the light properties directly in to each light shader. I was quite sceptical about the results though. It never quite got the results that stood up to the final finished spaces. Not even close really.

I am sure that one could write a light shader that could build a lighting model based on the standard illuminance information that lighting companies supply. It is nothing special really. It would mean using realistic lights with inverse square roll-offs and proper light temperatures though.

Realistic lights are not the easiest things to work with when lighting a scene. If you are comfortable dealing with dimmer values that range from 2000 to 12000 and managing scene units to get proper predictable lighting then you should have no problems. Quite a bit of setup though.

Hey,

Yeah I have a copy of Lightscape 3.1 and yes Autodesk did buy them. Still I thought it gave pretty good results. Especially for the time. I believe these light values are being calculated by the companies in photosensitive rooms with walls that have tons of photo recepters on them to record the light casting data so I believe its a bit more involved now than it was back then and more accurate. Still its very cool and we have gotten some good preliminary results with it in Mental Ray.

Cheers,
Nate Nesler

You could probably rig up the same setup in houdini using a point cloud to behave like the photoreceptors in lightscape.

I am glad that lightscape has progressed. Sounds like it is a much better tool now but the discreet website stopped support on it July 31, 2003. They call it a legacy product.

it is now inside the belly of Max.

Not really, Lightscape is long dead unfortunately (last version was 3.2). I don't think they ripped the tech out of ls and stuffed it into VIZ. From the renders I've seen, what passes for radiosity in 3D Studo VIZ (and max now?) was not really close to the results you could get with lightscape.

Hey Guys,

No I meant Mental Ray has the Light Profiles from the Photoreceptor rooms its more advanced than the Lightscape Method. Lightscape was cool I had real trouble getting support from the company before Autodesk took over it. No right now you can get a higher level of Radiosity in Mental Ray when their lights will duplicate the data from the Light Profiles and get as close a match to the actual light as I can imagine. Thats why I was wondering if Mantra had this capability because I would really like to be on only one rendering software package. I don't want to have to try to match the two up and do more compositing between the two rendering packages.

Cheers,
Nate Nesler

This is all doable in mantra. Like I said before, we need a shader that takes the light information from the cut sheet.

Are you thinking of importing the geometry with the raydiosity solution already baked in to the geometry or are you thinking of just using GI in mantra?

Hey Jeff,

We will probably try both and see which one gives the best result. Baking might be the solution in order to get the two renders to talk to each other. But if we can do a GI approach and then bake it that would probably be even better because then it will make it easier to do outside lighting along with indoor. Either way the final result will be backed because of speedier renders.

Cheers,
Nate Nesler