The Vector Dimension

Moving successfully between
3-D and 2-D

Realistic 3D handling takes your 2D drawings into new creative territory.

A few months ago I looked at the importance of 3D handling to realistic illustration and the ways in which the major 2D drawing apps have begun to embrace the fact. There’s still a huge way to go however, so is there an alternative way of bringing your vector drawings to realistic life?

The ideal would be to simply extend your existing 2D skills into the third dimension and there’s one program that promises to do just that – SketchUp 3 from @Last Software ($475). In many ways SketchUp operates like a traditional 2D vector application with its Drawing toolbar providing the basics of rectangles, ellipses, curves, polygons and lines. As you draw, coloured dots and coloured lines keep appearing to help you align your work to the existing geometry by snapping to existing edges, midpoints, tangents and so on. Once you’ve drawn your objects you can select and group them and reposition, scale and rotate them with the tools on the Edit toolbar. This also provides the Paint tool with which you can apply flat colours and tiling bitmap textures.

So far so ordinary. Where SketchUp moves into entirely new territory is with its Views toolbar. Here it becomes apparent that so far we’ve been working in Top view looking down on our artwork from above. If we switch to the Front, Back, Left and Right views there’s not much to see as of course our artwork is completely flat. If we switch to ISO view, however we get an isometric projection which by default shows a perspectivized view just as it would look to a human observer looking at the artwork laid out flat on the ground. And using the tools on the Camera toolbar, in particular the Orbit tool, you can interactively and instantly set up this perspective view exactly as you want it.

This is a big step forward compared to trying to manage perspective in a traditional drawing program, but so far all our objects are still resolutely two-dimensional. But this is where SketchUp works its magic. Using the Push-Pull tool in the Iso view you can simply select your shapes and drag them upwards to extrude them, instantly turning a rectangle into a cube for example. Even more powerfully you can use the other Edit tools with these new 3D objects. By scaling the top surface of the cube down towards a point for example you can create a pyramid, while moving the surface creates an angled effect. When you get to grips with just what’s possible – offsetting surfaces, rotating planes and edges in 3D space and so on – you can create advanced 3D shapes in seconds.

Even more impressive is SketchUp’s ability to interactively draw 3D shapes from scratch. This is possible thanks to its underlying “inference” engine. We saw this at work in the constantly appearing coloured snap lines when drawing in 2D and SketchUp’s stroke of genius is to simply extend the same idea by looking for connections to the existing 3D geometry and the main drawing axes. It takes a bit of getting used to, but eventually it becomes second nature. Adding a roof to our extruded rectangle, and then a dormer window for example takes just a few lines and a few seconds.

SketchUp seamlessly moves vector drawing into the third dimension.

Being able to literally “sketch up” a 3D model like this is creatively exciting, but so far we’ve only been talking about straight lines and flat surfaces and of course the real world is much more complex than that. So what do you do if you want to add a curved object such as a cylinder or cone? It doesn’t look like it’s a problem – simply add a circle and then use the Push-Pull tool to turn it into column and the Scale tool to turn it into a cone.

It’s important to realize though that, behind the scenes, SketchUp is using a workaround - breaking the circle down into short line segments that it then stretches into co-planar surfaces. Thanks to the program’s in-built and customizable smoothing when it comes to onscreen display, the cylinder and cone look curved but, if you turn on the display of hidden geometry, you’ll see how the effect is actually produced with flat planes. Generally the workaround works well - after all you can always break down any shape into a series of smaller triangles which by definition are co-planar. However it would be almost impossible to draw an advanced curved shape like a sphere from scratch – instead SketchUp provides these as comparatively crude ready-drawn components - and you can forget about creating realistic organic 3D objects such as a human face or figure.

SketchUp certainly isn’t a replacement for a traditional 3D modeling package (its main target market is architects), but it’s still surprising how realistic the scenes it produces can be. This is firstly thanks to SketchUp’s use of bitmap fills which means that walls really look like solid brick and lawns like growing grass. It’s the speed with which these perspectivized bitmaps are handled which is extraordinary enabling you to move the camera viewpoint through your model while its rendering is updated in real-time. Just as impressive is SketchUp’s handling of shadows. You set these for the scene as a whole by setting the location and time of year and day and SketchUp creates accurate shadows based on the position of the sun. These shadows are geometric projections rather than softened bitmap effects but they still go a long way to bringing the drawn model to life.

SketchUp’s combination of 2D drawing and 3D modeling certainly helps produce eye-catching illustrations within the program but it’s also important to be able to use these drawings as part of larger workflows. SketchUp’s central crossover role here is especially apparent with its ability to output its vector illustrations to multiple formats. The simplest option is to output your drawing as a bitmap such as JPEG or TIFF (you can even output camera-based animations to AVI format). Much more impressive is the fact that you can output your scenes as 3DS models complete with texture maps ready for import into a traditional 3D modeling app.

Here we’re more interested in maintaining the scalable, resolution-independent vector nature of SketchUp’s 3D illustrations. For further work in a CAD program SketchUp supports output to the technical DXF and DWG formats, but what we’re looking for is further creative handling in the mainstream drawing apps. Again SketchUp promises to deliver with its ability to export to the EPS and PDF formats which Illustrator, CorelDRAW and FreeHand can then import. Working like this, it looks as if SketchUp should make a natural partner for originating 3D elements to help make our 2D illustrations really stand out.

That’s true to an extent but in practice the major elements that brought the SketchUp model to life – bitmap textures, realistic projected shadows and onscreen smoothing - are largely lost in the conversion to EPS/PDF. With a textured and shaded sphere, for example, the bitmap texture is converted to a single appropriate flat colour and the on-face shading information is then used to darken this colour appropriately on each of the clearly visible planes that make up the faceted pseudo-sphere (for some reason the ground shadows are lost completely). It certainly gives the impression of 3D but in a less than realistic and undesirably computerized way.

SketchUp’s vector pdf/eps output lacks realism.

It’s a big step towards the goal of adding realistic 3D handling to the main 2D illustration apps but there’s no hiding the sense of disappointment. So is there another way? The ideal would be a dedicated 3D modeler that allows its images to be exported to a standard vector format. That way we would break free from SketchUp’s strong bias towards clearly faceted drawings and be able to produce much more sophisticated and organic 3D objects. The problem is that the dedicated 3D modeling applications have a different agenda. Rather than outputting scalable drawing-style vectors they are working with advanced procedural materials and texture maps to produce the most photo-realistic ray-traced bitmap renderings that they can.

It looks like a dead-end, but then I remembered Electric Rain’s Swift 3D ($169). This is a 3D modeling program with a difference as the whole application is tailored towards producing Flash-based SWF animations. Flash is a vector format so sure enough, while it doesn’t exactly advertise the fact, Swift 3D also supports the export of single frames to the EPS and Illustrator AI vector formats which is just what we are looking for.

Considering its price, Swift 3D provides some surprisingly powerful 3D modeling capabilities, beginning with a range of pre-provided primitives, such as planes and spheres (unlike SketchUp you can control the number of polygons that make up the sphere and so its smoothness). You can also create your own 3D objects using the dedicated Extrusion Editor and Lathe Editors. It’s simple for instance to import a flat logo from Illustrator and then extrude and bevel the results to produce a three-dimensional version. More powerful still is the ability to import 3DS models. Working in this way it’s possible to bring in scenes from just about any 3D modeling application from SketchUp buildings right through to Poser figures and even simplified Vue Pro landscapes.

What really makes Swift 3D different though is its dedicated “RAViX” vector rendering engine. In fact the technology is so special that Electric Rain has also developed it as dedicated rendering plug-ins for 3ds max and Lightwave ($295) and licensed it to other developers such as Eovia who market it as VectorStyle ($129) an add-on for Carrara. In each case the core settings to choose from are the same. Firstly you need to control the lines in your vector output by setting whether to outline anything, just the object’s edges or the entire polygon mesh and, where relevant, the level of internal detail that the RAViX engine should look for.

Electric Rain is the master of vector rendering.

It’s the handling of fills though that is the real key to RAViX’s vector rendering capabilities and success. The first option on offer, Cartoon Single Colour, is the simplest as it renders each object as a single colour so that a test sphere outputs as a simple flat circle. That’s hardly convincing but you can improve the perceived 3D appearance by switching on Shadows, Reflections and Specular Highlights (small gleams which indicate the shininess of the material), all of which immediately bring an otherwise flat fill to 3-dimensional life.

The real key to adding realism though is to increase the number of colours generated for each object with the Cartoon Two Colour, Four Colour and Average Colour options. In each case the RAViX engine breaks down the model into groups of polygons that are similarly angled to the light sources and so can have the same colour applied to them. The biggest leap comes with the last Cartoon option, Full Colour, where each polygon (up to 200,000 in total!) is individually coloured. And the RAViX engine takes things even further with its Mesh Gradient fill option where every polygon is filled with a linear gradient. The results can be astounding. I loaded a dinosaur 3DS exported from Poser into Swift 3D, for example, and applied one of the program’s procedural textures and the resulting fully scalable vector gradient mesh was almost indistinguishable from a bitmapped render.

Now all we need to do is to import the gradient mesh into a 2D drawing application and we have the best of all possible worlds – a fully scalable, near photo-realistic 3D model that is ready to be further processed in your drawing package of choice. But there’s a problem. The gradient mesh option is only available when outputting to Flash SWF format (I’m not sure why as linear gradients are PostScript-compatible) and neither Illustrator nor CorelDRAW support SWF import. FreeHand does however, so it’s possible to load the 3D gradient vector image and very striking it is too - no matter how large you scale it. Unfortunately the SWF is embedded as a movie and so can’t be broken apart for further processing. And, when you output it, the anti-aliasing that makes it look so good onscreen makes it look undesirably soft in print. For the moment then it’s back to the Cartoon Full Colour option for the most realistic PostScript-friendly rendering and to the other Cartoon options for a more hand-drawn appearance and easier handling.

Vector rendering involves a trade-off between quality and editability.

It’s another disappointment but it’s important to recognize how far we’ve come. With SketchUp it’s possible to take existing 2D drawing skills into the third dimension, successfully straddling the worlds of 3D modeling, CAD and creative drawing. And with Electric Rain’s Swift 3D and RAViX rendering engine, it’s possible to get your favourite 3D modeler working hand in hand with your favourite drawing package to give your illustrations real depth - and a creative edge.

Tom Arah

April 2004

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