CGSociety

Jack Greasley, developer and Product Manager at The Foundry, takes CGSociety for a look around Mari, the new texture application.

CGSociety :: Technology Focus
25 May 2010, by Paul Hellard

Mari is a texture projection painting system developed by The Foundry R&D department and the texture department at Weta Digital. This 3D texture application is able to handle up to 30K textures and produce production-ready assets.

The development of Mari started just after 'King Kong'. "Doing the texturing for 'King Kong' was a bit of an epic struggle," says Jack Greasley, Product Manager of Mari, now at The Foundry. "This was mainly because of the tools that were available at the time. After 'King Kong', the 'Avatar' art reel turned up, we all had a look at what we would have to go thru and quickly decided that we couldn't go through all the problems we'd had on 'King Kong' and decided we had to write a new system that met the crew's requirements. At that point, I was brought in to design Mari from scratch for them."

It was actually 13 or 14 months before it was usable in any way, shape or form. There was a very embryonic version of Mari at that point, mainly because Jack and his team had to do some fairly heavy engineering under the hood to make sure they could get the scalability that was required. The first exercise were some sweat marks for a character in 'Avatar', the six legged horse. "This was a fairly simple set up," says Jack. "From that point onwards we released features day by day for the artists, and sometimes two or three times a day."

"Having that incredibly tight turnaround with the artists meant that we got an awful lot done in a relatively short space of time, and pretty much everything we put in there was directly needed in production," Greasley continues. "It was taking the top three things out of the pile of 500-things-to-do list and doing them as quickly as possible. I must say it was interesting developing Mari and doing 'Avatar' at the same time."

One of the program's strongest features reported in Mari is its interactivity. Even with real world production models of high complexity, with multiple 2K textures - the program is lightning fast and responsive. Through the use of some GUI and some very smart CPU programing, the engineering team has produced an extraordinarily interactive program.

2k Animated Textures

Jack Greasley admits it's very valuable to the team having been in the trenches while working on the program. "Sitting next to one hundred texture artists for 15 hours a day for three years, does get you some good insights into the way that they work and their needs," Greasley says. "It gave me the opportunity to concentrate on details that if I'd not been in that situation, I would have missed. I actually spent up to two weeks optimizing the time it takes for the 'File Open' dialog box to come up," he explains. "If I can save a few seconds where that dialog box is opened a few hundred times a day, among one hundred artists, that's a few hours saved for each day. It's little things like that gives a longer term view."

At Weta, Greasley saw the art reels of future projects coming in. By fixing the smaller issues with software, the confidence gained in the bidding campaign helped the crew get the longer view sorted out.

Avatar ©2009 Fox. All rights reserved. Images courtesy of Weta Digital. caption: “As a single asset I would have to say I'm most proud of the Hometree. It has incredible detail on the surface of the bark that is only glimpsed at in the really close-up shots of the tree.” - Lead Texture Artist on 'Avatar', Michael Cox.

Mari at work.

“Almost every asset rendered by Weta for Avatar was painted to some extent in Mari," says Jack Greasley. "A typical character was around 150 to 170 patches, with 30 or more channels (specular, diffuse, subsurface, etc) and 500k polygons at Sub-division level 1. The full texture set ran to several tens of gigabytes, all of which could be loaded in Mari at the same time. The biggest asset I saw being painted was the shuttle which came in at 30Gb per channel for the fine displacement detail (500, 4K textures). Assets of over 20M polys can be painted.”

Weta has kept the creation of Mari very close to its chest. Having now been brought into The Foundry, Mari has a lot to offer the industry. "Every piece of software has its own strengths and benefits, and I think Mari has tackled the texturing process from a strict purist point of view," says Greasley. "Mari definitely does address a raw requirement which has been brewing around for the past five or six years, so it's good in that way."

Painting
Mari is a projection painting system, a system that removes a lot of the drudgery from texture artists' daily life. One of the things that was found was that the way other software deals with images, artists werer spending a lot of time being 'data wranglers', copying images from Point A to Point B; keeping stuff updated; not spending their time painting. Now Mari is half database system and half painting engine. It is designed to keep the texture artists painting, as much as they possibly can. The GPU optimisation, version-labeling, menu management and such, are all done under the hood, so the artist doesn't have to worry so much about that. Mari uses an OpenGL view. You don't need to lock the view or hit a menu item. Just spin the object round and start painting.

Lighting
Mari currently has a basic lighting system, supporting four positional lights, and ambient occlusion. There is an HDRI environment lighting module for the shader system which will take an EXR and that can be used for lighting. Mari has a number of different shader modules, mainly relating to specular lighting, channel layering, displacement previews, lighting models etc. Although Mari currently doesn't have a SSS shader, the shader system is extendable using GLSL so one could be added.

File Formats
The Mari production team looked for the most commonly accepted format and decided to begin with .OBJ. In later versions, there amy be a wider range, but the other software packages that Mari would be working with, all present .OBJ files, so there is no real hurry. Mari will be ready for Linux 64-bit for the first release with Windows support coming afterwards. A Mac OS X version is also on the road map for later release.

Limitations
The crew at The Foundry are still doing profiling on the ceiling of polygon management within the package, and at the moment, it can still handle a million models very well. Compound models can be handled very well, comfortably handles millions for single objects and all of this of course depends on your GPU and systems.

Color Management
Mari has a very flexible, display-time color management system. It allows many filters, lookup tables and collection operations at display time. Whatever color-space you bring your model in, it either can be converted, or it can stay in that color-space. If you wanted to stay working in a linear color-space, you can, and you can set up a display time filter to show the work in another color-space. Any shaders can be written and dropped in as well using the modular shader system. Mari has a modular GLSL shader system that allows you to custom write more complicated shaders from simple components.

Beta soon
Mari is in Alpha at the moment, being used at six sites on upcoming feature productions. The application was handed one of the hardest assets to work on, at one of these sites and the word is that, 'Mari ate it for breakfast!' There will be an extension of the Alpha program and a full product release nearing the end of the northern Summer. Plans for a PLE are also on the cards.

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