Film GIMP at Rhythm & Hues
Film GIMP came about thanks to the patronage of R&H and software development company Silicon Grail. Each hired an OSS GIMP programmer for a year: GEGL designer Calvin Williamson at R&H and GIMP maintainer Manish Singh at Silicon Grail. Silicon Grail founder Ray Feeney explains, “We had done some other open-source projects, such as film recorder drivers, and saw enhancing GIMP as an opportunity to do something with the Open Source community.”
Silicon Grail RAYZ product manager Craig Zerouni says, “We did a little work integrating GIMP into our compositor Chalice as a plugin. But in the end we decided a nonprocedural paint program didn't fit well into a procedural program like Chalice.” Silicon Grail was working with GIMP script-fu to create a series of Film GIMP commands that could be saved in Chalice. However, that work was abandoned when Silicon Grail developers switched to begin development on their new compositor product, RAYZ.
Zerouni feels a true procedural language is needed in the paint program, something like the language in RenderMan. Silicon Grail has lately acquired the Cineon source code from Kodak, including the program Retoucher. “Film GIMP was a useful thing for us to do”, says Zerouni. “We learned a lot about what paint should be.”
GEGL, the GIMP E Graphical Library, is an image-processing library based on GObjects. GEGL developer Calvin Williamson helped develop Film GIMP originally while at R&H, together with Ray Lehtiniemi from Silicon Grail. The next version of GIMP will be 1.4, but Film GIMP continues in development on a branch of 1.0.4. GEGL, whose design supports 16-bit channels, is due to integrate with GIMP 2.0, perhaps two years away. GIMP 2.0 is anticipated to bring the pro features of Film GIMP into mainstream GIMP.
Williamson says his current plan is to write a baby compositor for GEGL to test memory management for large images, multithreading, large composite trees and other heavy-duty professional requirements:
The classes that do image and memory management have been split from the actual image-processing classes. This allows one to write image managers that traverse the graph of ops in custom ways, or write custom caching or memory managers for handling memory management. The classes that hold information about ops as part of graphs, with inputs, outputs, regions of interest (all extrinsic op info), have been separated from image-processing classes (intrinsic op info) as well. This makes graph traversals cleaner for things like multithreading.
“GEGL is still in a very early phase and many classes are under construction”, says Williamson. “There is no official release yet, but you can download it from anonymous CVS. I have made quite a few architecture changes recently.” GEGL is a fully 16-bit image engine for future GIMP and other projects.
Both GEGL and Film GIMP seek volunteers to help with programming. Williamson says PDI, ILM, ICT and Sony studios have expressed interest, but so far have not provided programmers. Williamson welcomes programmers interested in writing image operators, memory management code and working on multithreading to join the GEGL Project. “Filling out the library and writing image operators takes time”, notes Williamson. “GEGL is an important part of the future for GIMP.” For programmers who find the GEGL timeline too far away, Williamson suggests helping with enhancing Film GIMP for the next year or so.
Film GIMP maintainer Dahllöf says, “We want to enhance Film GIMP by adding more tools for artists working on a sequence of frames. We want to make it easier for them to paint and clone from one frame to another one.” R&H uses a proprietary flipbook player called Flicks. A feature missing from Film GIMP is a flipbook playback mode so users can detect flickering. “Artists do use filters, but some of the filters in the main branch of Film GIMP are not useful in motion pictures. Artists want more control over filters.”
On the topic of open-source software, R&H principal software engineer Green says:
It's a big debate about releasing more of our proprietary software as open source, beyond Film GIMP. Most of our software would be difficult to use outside this building. It is tied to our production tracking system, PTS. Nothing will run without that.
Green says the biggest pro argument is to save on the high cost of training. New hires at R&H spend their first month just doing training. Having a pool of talent emerging from the universities already trained in R&H tools would help.