One of the biggest additions to the latest version of XSI are the polygon-editing tools. Apart from the point-moving capability that was already there, XSI now also sports a complete set of component-editing tools. You can select and extrude any polygon component, bevel them, collapse them, and subdivide faces and edges. There are a lot of other editing tools for components too, but the new set is perfectly good for any polygon-modelling tasks.
Like the rest of XSI, there’s a construction history, viewed in the Explorer window. All modelling operations are stored in a list, and each is selectable so you can revisit its parameters and make changes. If you don’t want to model in this way, you can select the new Immed switch in the Command panel. With this active, no history is stored and you must use the Undo feature to go back a step or two. The Explorer view has also been improved, giving you a clearer overview of your Projects, Scenes, Layers and Render Passes.
Along with low-level modelling tool improvements, there’s a neat high-level tool called FaceMaker. It’s a model of a head with a number of clusters linked to sliders with expressions – you can move the sliders (over 45 of them) to alter parts of the face.
XSI gets top marks for its implementation of Subdivision Surfaces, a totally new feature of the program. All polygon-based objects have a Geometry Approximation node used to subdivide the object. When you change the approximation value from the default 0 (no subdivisions) to 1 or above, the object becomes a subdivision surface. There’s no special command or operation; just turn it on or off as you like. The base mesh becomes the control cage and is displayed in wireframe, so you can still model it as usual. You can also convert polygon objects into Subdivision Surfaces using a command. You achieve a similar result, except for an additional Doo-Sabin smoothing algorithm over the default Catmul-Cark method. You can switch between them to suit your model, and even when you use 5, 7, 8, n ... point polygons, the surface is always smooth and free from glitches.
Animation is one of XSI’s strong points, but there’s still room for improvement. The Animation Editor has received some attention: the channel list at the left now looks like the Explorer view, and a new Dope Sheet view has been added. To the left of the interface are the toolbars: Model, Animate, Render, and now Simulate. This last has been added to accommodate the new dynamics tools, the main addition being Cloth. XSI cloth uses a spring-based model for creating realistic cloth animation. Ordinary polygon or NURBS objects can be used as cloth objects, so you use the same tool set to make clothing as to make the rest of your models.
The Simulate toolbar is where you’ll now find the particle tools, which have also been improved so you can change particle parameters without having to re-compute from the first frame. Weight maps can be used to control Emission Spread and Speed, for example, simply by connecting them in the Render Tree. The Render Tree is unchanged, but it’s still a simple way to leverage the power of the MentalRay renderer.
Softimage have done admirably with XSI, which is far slicker and smoother than Maya in some areas, though maybe not as deep. Such things as fur rendering are still missing, though this is not a major shortcoming. A lack of support for projected curves and trims is, however.