Renderman????

[gmask]

Originally posted by kiaran
Hasn't ray-tracing been around for ages? I know many major movies have used renderman for years. How did they render reflections/refractions without raytracing?

Yes it has but raytracing has been disabled in the comemrcial version of renderman until recently. Some users used BMRT for the raytracing and connect the two renders useing a technqiue called Frankenrender. You can fake most reflections by rendering a second cameras POV and then using it as reflection map. YOu can sort of fake refractions in a similair way by rendering a "map" of the area being refracted and then texturing it on the refractive surface. Caustics are also faked with projections.

You'll notice that in most of the PIXAR movies there really are few instances of refractions.

So then you ask why is PRman so popular in film. Well it is very fast..for onething it doesn't calculate raytracing. It alos ahs a very open method for writing powerful procedural shaders and it's support for NURBS surfaces made it a popular choice for highend visuals early on. You can fake GI in pretty mcuh any renderer with the placement of lights so it is only recently that it was possible to render GI in production because it is very computationally expensive.

For most users these days I do not think PRman is the way to go for rendering. It's expensive and complex to use in order tog et the features that make it powerful. However it still holds it's palce in the film world although I imagine it will be getting alot of competition from Mental Ray in the years to come.

Also there are various Renderman compatible renderers out there some of which are free for those who want to learn more about Renderman without have to pay $5-$7k just to get one license of it.

[kiaran]

Thanks Gmask for clearing some things up. I'm still amazed that Renderman can stay afloat considering you could buy a seat of Maya Unlimited for the price of ONE render only program that doesn't seem to do anything more than Mental Ray which comes FREE with Maya. The speed issue is intriguing. I would be interested to know just how much faster Renderman is. And now that you have mentioned it, Pixar movies don't use many reflection/refractions.

For $7000 you could buy a kick ass renderfarm if speed really that much of an issue. I heard that the scene from the Matrix where the huge arm machine thingys are harvesting those little glowing eggs was completely rendered in Renderman. They wrote a custom shader so that as those little mech-spiders guys ran over the eggs there legs cause a slight glow when they touch the surface of the egg. These kind of 'dynamic' shaders are interesting. I guess I'll leave Renderman to the big leagues... for now...

Before I leave, I'd like to post another question. Does anyone know if or how you can make 'dynamic' shaders in Mental Ray for Maya?

Cheers,

Kiaran

PS: I just realized this post probably belonged in the 'Rendering Section', sorry bout that. :hmm:

[Hazmatman]

It is hard to explain why renderman is so good while other programs have more features. Renderman is simply a joy to use, and it produces high-res beautiful images in the blink of an eye, it is truly amazing. Pixar advocates the use of a complex light setup, instead of GI, and the same goes for raytracing. As a matter of fact watch some of there movies, you wil find few if any examples of which GI, radiosity or raytracing are used, and I mean 1 or 2 instances in the entire film.

Pixar is a revolutionary studio which has a top of the line renderer, which was designed to fit their pipeline, You can achive all the same beutiful art they have with Maya and Mentalray. Don't set pixar as a standard as they are far above individuals like us, go and create your own visuals that inspire and make us imagine.

[gmask]

Well PIXAR uses renderman for their projcts so it is not sales alone that supports it's development but rather the films that PIXAR creates. Other companies have proprietary renderers that they do not sell to the public.

>>>Does anyone know if or how you can make 'dynamic' shaders in Mental Ray for Maya?

Actually you can do some things like this in Maya ..at www.highend3d.com there is a shader that shows a simialir effect and it the example happens to be a spider.

[kiaran]

Thanks for clearing everything up for me. Renderman sounds like fun. I hope I have the chance of working for a studio that uses it sometime.

Cheers,
Kiaran

[Miyazaki]

OT:
'Any significantly advanced technology is indistinguishable from magic!' - Arthur C. Clark
Any technology that is distinguishable from magic is not sufficiently advanced.
- Gregory Benford :)

[Kinematics]

Thanks for asking the question kiaren...wow that question was actually at the back of my brain for a long time. I just southa presumed that it was 30 times faster and produced higher quality renders although i never checked out the program ever.

THanks that explains alot

[playmesumch00ns]

The main benefit of PRMan for film companies is speed: particularly displacement and motion blur, which add a fraction onto your render time, compared to adding a factor of 10 with some other renderers.

The important thing to realise here is that film companies that use PRMan (that's most of them) run it on large renderfarms. And shots still can take days to render. What's so good about PRMan is that a particularly complex frame may take days to render, but it will render. A lot of other solutions (I'm thinking particularly of mental ray) still involve a lot of finger-crossing.

As for GI/raytracing, would you say that any of Pixar's films have been lacking for not using it? As for how much is there, well a certain spaceman had a very shiny helmet in Toy Story 1 and 2. The first Pixar film to use raytracing was A Bug's Life, for the scene where hopper unleashes a torrent of seeds on the other grasshoppers. The bottle the seeds were in were rendered with BMRT as a "ray server", which just means that PRMan called BMRT whenever it needed to shade a pixel that contained a part of the bottle.

kiaran, the "dynamic shaders" you're talking about are just called "shaders", and are not much different from Maya shaders. You can write your own shaders for Maya using the API, and providing you know C++, it's not any harder than writing shaders for RenderMan. The only difference is that RenderMan uses an interpreted language known as RenderMan Shading Language, which makes the process of shader writing a lot easier for the artist (as opposed to the programmer).

You can also write custom shaders for mentalray. Again, you need to know C, but it's slightly easier (imo) than writing shaders for Maya. You can download the mentalray headers and stub library from Alias' homepage and start writing mentalray shaders.

Pixars decision to start adding raytracing and photon mapping to RenderMan has probably been part influenced by the increasing feasibility of using GI solutions in production due to hardware advances, and part due to the whole Entropy fiasco. As it stands, the GI/raytracing in PRMan 11 is not complete, nor is it particularly fast.

Even in its present primitive stage (and it will get a whole lot faster over the next couple of releases), from the point of view of a shader writer, PRMan provides some incredibly exciting features, and it all fits neatly into the RenderMan standard.

If you get the chance to use PRMan (or any other RenderMan renderer for that matter, there are plenty of free ones), take it, but be prepared to put some time in learning it to use it to its full potential.

[capin_crunch]

It looks like someone has read the companion and "advanced renderman".

I am currently reading the companion.

cheers
-capin_crunch

[Hazmatman]

Concerning raytracing, Pixar only used raytracing for one scene in Toy Story, the scene when Buzz is standing on the bed after he arrives. All other reflections were environmentally mapped, or using the old camera trick I’m sure you read about in the documentation. There are a few major reasons Renderman sticks out from the rest:

• Speed
• Complex shaders
• Flexibility between platforms
• Networked rendering

I think radiosity was added to the latest version because Pixar wants to stay in the curve with new technology, and they certainly have. But one thing that Renderman lacks is a GUI, that can handle the amount of commands and such that the shader language gives you, I don’t see this as being very possible, as the average Renderman user doesn’t need a GUI.

I don’t think that Pixar would put GI to work in any of there feature films.

[jeremybirn]

The full Renderman Artists Tools package for Maya adds a new PRMan menu to Maya's GUI, and new palettes for linking, previewing, and adjusting shaders. Other animation packages have other GUIs available for controlling renderman. (Of course, in big studios, whether you are dealing with PRMan or Mental Ray or an in-house renderer, you're bound to see people writing and compiling new shaders, not just linking and adjusting prewritten ones though a GUI, but that's their choice.)

One of the big issues that someone may have mentioned before but I didn't see above is anti-aliasing. In many renderers, when you double the oversampling for smooth antialiasing, doubling the samples doubles the render time. In PRMan, the shading process has been separated from the sampling process, such that doubling your number of samples doesn't increase your render time by nearly as much.

-jeremy

[kiaran]

Thanks for the great feedback guys. After reading through all your responses it makes me really want to sink my teeth into learning how to write shaders. All I can say about Renderman is:

:drool:

Cheers,

Kiaran

[Anteru]

If you want to use RenderMan without paying for PRMan, you could try Aqsis which also supports lots of the important features like Curves, DelayedReadArchive, full programmable shaders, SDS, NURBS, etc. Cause shader writing is more an art than a science, and only practice will make you good. You can achieve a lot just with the right shaders.

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.