Faith

When rendering scenes, it is oftern usefull to be able to render parts of the scene in seperate layers, which can then be put back together by a compositor. Different applications provide varying levels of support for rendering in layers, but it is perhaps more usefull to seperate this part of the process from the 3D animation process, as it is essentially a technical issue of interest only to the rendering TD, and compositor.

Faith is a tool which reads a RIB file, and allows the user to split it into a number of layers. It is based on the Angel rendering engine.

Initalisation

Faith should be started from the command line by typing "faith xxx.rib yyy.layer". If the layer file does not exist it will be created, with all of objects being initialy placed in a default layer.

Usage

Two windows are displayed, showing two layers from the scene. By default clicking on an object moves it from one layer to the other. By pressing 'c' or 'd' objects may also be copied between layers or deleted. 'm' can be used to select matte mode, where objects can be toggled into matte's.

To work with a different layer, simply right mouse in a window, and you can change to viewing that layer. Selecting New from this menu creates a new layer. Due to UI limitations, you need to type the name of this layer into the shell window from which you started the program.

Rendering

The result of running Faith is an ascii file which describes which objects are in which layers. To render a layer you need to run "extractFaith xxx.rib yyy.layer layername". A RIB file will be sent to stdout, which can then be piped to your renderer.

Limitations

Faith is very much a prototype and no doubt suffers from a range of problems. Those which are currently identified are as follows:

Faith currently ignores Curves and Points.

An Object is defined by the name attribute. While Houdini names things at a relativly usefull level, Maya tends to go a little overboard on these. A more flexable way of selecting groups of names should be implemented.

The extract program should probably change the output filename. Currently each layer rendered will overwrite the previous layer unless you take care to avoid otherwise.

Extract may "ignore" certain primitives. If these are reported then they will be swiftly fixed.

Downloads

The current release of faith can be downloaded for freeBSD, Linux, NT and SGI .

You'll also need a suitable extract program ( freeBSD, Linux, NT and SGI ). As always could any users please register their usage by emailing me.

Ian Stephenson.
DCT Systems
NCCA,Bournemouth University