Product Reviews

In its simplest form, Piranesi is a painting package with natural brush effects, much like Painter or parts of Photoshop. However, it uses a proprietary file format (EPIX, or Extended Pixel Format) that allows it to perform its clever stuff.

An EPIX file is a greyscale image of a model, but one which contains channels that store information about the depth of a pixel - that is, how far away the point in the image was from the camera when the image was rendered in a 3D package.

Most 3D packages can output EPIX files. Even if yours can't, Piranesi contains a utility called Vedute that converts most popular 3D file export formats (DXF, OBJ and so on) into EPIX files. We have to say we found this utility's interface a little clunky in use. However, we were using it to import SketchUp files and, as of version 3.1, SketchUp now supports native EPIX export.

Piranesi uses the depth and other information to limit the effects of painting to surfaces in the model. Because each pixel in the image 'knows' where it was on the original model, Piranesi can pick out and paint pixels that, say, all represent a single plane in the model or pixels that represent faces that all have the same orientation. Other attributes, such as material ones, are stored in the EPIX file, enabling Piranesi to paint only over pixels that represent a particular material in the original model, so you never go over the edges.

Piranesi contains a number of locks (Plane, Orientation, Material and Colour) that must be set manually before painting can start, but the program intelligently chooses the particular lock according to the first pixel you click on. If, say, you choose Material, and click on a pixel that represented a brick material in the original model, only that material will be painted in the EPIX file.

Bristle while you work

The interface is a little unusual, but the controls for the brushes should be familiar. Size, softness and orientation can be user-defined and, of course, Piranesi can use bitmaps

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to create custom brush textures.

One nice feature is the ability to have the brush profile rotate as it moves across the page. This mimics the 'wrist-brush tip' interaction that occurs in real life - great for asymmetric brushes.

The difference, though, is that Piranesi also has 3D brushes: these use EPIX information to orient themselves on planes in the scene. The brush profile literally 'crawls' over the surfaces of the model. However, you still have to choose a lock to constrain painting effects to surfaces. You get the impression the 3D brush should have the Orientation lock turned on by default.

Piranesi's other mass-fill tool is the familiar Bucket. This can be used exactly as in other programs, but if it's combined with Material lock, it can be used to apply a style selectively everywhere it appears in the scene.

These brush settings are all very well, but you need some method of managing them. For this, Piranesi provides the idea of styles. A style is simply the sum total of settings that make up the appearance of a brush: colour, opacity, blending mode and any associated bitmaps and locks. Each style can be grouped together with other styles into a library, and libraries can be accessed from the Styles Browser window. This means you don't have to remember settings and, more importantly, you can define house styles that can be easily applied to EPIX files to produce what look like hand-rendered perspectives with the application of a few styles and brushes. Piranesi ships with a battery of ready-made styles to apply to scenes.

The program also makes it easy to add elements that are difficult to add in a 3D package - for example, trees and people. It does this using Cutouts, simple 2D images that can be positioned anywhere in the scene. However, because of the EPIX format's depth information, Cutouts scale according to where they're placed in the scene, and obscure, or are obscured by, other Cutouts, maintaining the overall perspective. Cutouts can also be made to cast shadows automatically, removing one of the biggest headaches in compositing. Cutouts can then be 'burned in' to a file to allow other Piranesi styles to be applied to them.

Style guru

Piranesi is a welcome addition to the Mac, as it's remarkably easy to produce convincing results using the standard styles. Defining your own convincing styles can take a little more thought, a process not helped by the tutorial manuals, which range from unclear to over-explicit, and the HTML-only reference manual. All in all, though, it's a compelling tool in the Mac artist's armoury.