Drawing Deep - Moving from 2D to 3D

The 2D Drawing Applications'
3D Capabilities

It's one of life's smaller ironies that, while the world we live in is three-dimensional, the drawing packages we use to illustrate and recreate that world are resolutely two-dimensional. Programs like CorelDRAW, Illustrator and FreeHand are ideal for producing the flat design for a wine label, for example, but reproducing that label on a realistic wine bottle on a realistic table in a realistic room is another matter entirely. So how do you go about giving your work real depth?

Some principles, such as that far away objects are smaller and appear more closely packed, are almost instinctive but the most important mechanism for successfully recreating the illusion of depth, Linear Perspective, is anything but intuitive. So much so that it was only in the Renaissance that the principles of one-point perspective were rediscovered from the Romans and and only in the 17^th century that the same was achieved for two-point perspective.

The central concept here is understanding that lines that are parallel to the viewer and receding appear to converge to a vanishing point. For a one-point perspective, imagine that you are looking at large cubes face-on and so parallel to the picture plane. You will see that the edges of either the top or bottom face - depending on whether the cube is above or below your horizon/eyeline - and the visible side face all converge towards a single distant vanishing point on the horizon. For a two-point perspective, imagine looking at rotated cubes that are not straight on. Here you will see the edges of both left and right side faces converging on two separate vanishing points and the edges of the visible top or bottom face converging on both (for a good introduction to linear perspective see http://www2.evansville.edu/studiochalkboard/draw.html.)

Perspective and realistic 3D shapes can give your 2D work new depth.

When drawing receding flat surfaces such as walls, buildings and so on this manual approach of drawing vanishing points and convergence lines might sound manageable but the complexity rises steeply as soon as you want to draw non-linear shapes such as circles and text. Imagine having to realistically hand-draw paintings on the receding wall, for example, or manually producing illustrations to show how your flat-on packaging design will actually look on a rotated 3D box. Of course for the number crunching involved in geometric challenges such as this, the computer comes into its own.

The first major 2D drawing package to graft on perspective control was CorelDRAW right back in version 2 and the implementation today is largely unchanged - simply select your object or group and select the Effects > Add Perspective command. This surrounds your selection with a rectangular bounding box divided into a grid of squares and, using the Shape tool, you can then drag any corner either in or out to apply a perspective to your object(s). By default a 2-point perspective effect is produced but, by holding down Ctrl or Shift, you can produce the more common 1-point perspective effect and by holding down both you can produce the most common centred, head-on perspective effect.

As the presence of the onscreen grid suggests, the perspective effect is simply an envelope distortion in which the contents of each original square on the grid square are mapped to the new distorted version. The main addition is that, where the bounding box's edges converge, either one or two vanishing points appear onscreen (you might have to zoom out to see them) and you can interactively drag these to control the effect. This is particularly useful as it means that you can share the same perspective view between multiple objects by first marking the position of one object's vanishing point(s) by dragging on guidelines and then quickly lining up the other objects' vanishing points on the same intersection.

Creating a truly realistic 3D scene in this way is still asking a lot but even the simplest perspective effect can really make your work stand out as our brains are tuned to reading the depth information that perspective distortion implies. If you drag on the limpest and flattest clipart character you can find, for example, and then place it over a rectangle to which you've applied a perspective the rectangle is seen as the receding ground and suddenly the clipart springs to life as part of an implied scene (adding a drop shadow helps the illusion further). And the advantage of the computer is that it's just as simple to add perspective to complex objects such as text or grouped artwork (though sadly not to CorelDRAW's bitmaps, fills, symbols or paragraph text) as it is to a rectangle. In this way it becomes reasonably straightforward to add perspectivized artwork to our gallery walls or to the sides of our cereal box.

Even basic perspective effects can still be effective.

CorelDRAW's pioneering capabilities show the immediate benefits of perspective control, but they are fifteen years old now. So how do the other major drawing packages compare? Surprisingly, throughout its long life, Illustrator's in-built control has been weak and hidden away. However if you dig in the help file you'll discover that, if you begin dragging a corner handle to resize an object or group with the Free Transform tool, if you then hold down the Ctrl, Alt or Shift+Alt+Ctrl key combinations you can produce 2-point, 1-point and centred 1-point perspective effects. With no control over vanishing points however this is seriously disappointing.

Things are at last looking up with Illustrator CS's new 3D capabilities. In particular the new 3D Rotate command can take any 2D object or objects and rotate them to any angle in 3D space either interactively via the dialog's track cube or numerically. To then produce the converging lines effect necessary to give a realistic illusion of depth you set the dialog's Perspective setting, designed to simulate the effect of a lens angle, to any figure between 0 and 160 with larger figures creating the illusion of greater depth.

It's a big step forward especially as the effect can be applied to imported bitmaps and fills which makes a huge difference, say, for adding real paintings to the gallery wall or creating a ground plane that actually looks like grass or tarmac. And best of all, because the effect is non-destructive, you can always fine-tune it later, save it as part of a style and even blend your effects to produce Flash animations. There's one major limitation to the Illustrator approach however - there is still no role for vanishing points so it's difficult to co-ordinate effects to produce a realistic scene rather than just standalone receding objects.

FreeHand comes to the rescue with a completely different approach to perspective in the form of its Perspective Grid introduced in version 9. In fact this works similarly to the way in which traditional artists work by setting a horizon with fixed vanishing point or points and then drawing a grid of converging lines to these points for the vertical and horizontal planes onto which they can draw their receding objects, say to add multiple windows or paintings to a wall. Traditionally to then add other perspectivized objects on different planes, say to draw the opposite wall and windows, they rub out the existing grid and draw a second and so on.

The beauty of FreeHand's computerized system is that it's easy to instantly define your grid by setting the the grid cell size and interactively fixing your horizon and vanishing point(s). More usefully you can then simply drag the vertical and horizontal planes into position as necessary using the Perspective tool. Most useful of all, is the ability to automatically attach your 2D objects to these grid planes. And, once attached to the grid, you can move your object up or down or in and out along the plane and it is not only automatically distorted appropriately but scaled as well so that you can be sure, for example, that your windows or paintings will look in proportion on the wall.

FreeHand's perspective grids let you co-ordinate your perspective effects to create 3D scenes.

It's another big step forward but again it's by no means perfect. To begin with, the FreeHand implementation can't handle bitmap objects and object fills aren't perspectivized either. More importantly the whole process is hardly intuitive - for example to attach your objects to one of the grid planes you first have to begin moving the object or group with the Perspective tool and then hit one of the four cursor keys and, if you decide that you want to resize the object while maintaining its perspective, you need to do this with awkward keyboard shortcuts. And to top it all, the help is so inadequate that only a fraction of FreeHand's userbase will be taking full advantage of this unique feature.

Extrusion

By repositioning your perspective grid planes you can co-ordinate effects to create basic shapes such as cubes and tables and basic scenes such as rooms, but this remains a complex chore and there's no flexibility if you decide you'd prefer another view of your work. The biggest limitation of all, and true of all three packages' linear perspective capabilities, is that they are designed to deal only with flat objects such as walls, roads, pictures, text and so on. And of course in the real world most objects aren't actually flat at all - they have depth and volume. To take our work to the next level we need a better way of creating more advanced 3D shapes.

In fact the solution, extrusion, is a simple extension of the same underlying principle of receding parallel lines converging to a vanishing point though in this case the lines recede from around the edge of the selected shape. Again the drawing application that pioneered the development of this form of 3D handling was CorelDRAW back in version 2. Nowadays the easiest way to create the effect is via the Interactive Extrude tool. To create a realistic box/cube, for example, all we need to do is select a rectangle and then drag off in the direction of the vanishing point and set the desired depth by dragging on the cross-bar on the extrusion control line.

If you create the extrusion with no fill, it is presented onscreen in wireframe format which shows exactly how the effect is produced - effectively a second smaller version of the selected shape is offset and converging lines drawn from points around the edge of the first object to the equivalent points on the second. More usually you'll create a solid shape via a filled extrusion in which case those faces that make up the object geometry but which are currently hidden are removed from the final effect, as you can see if you use the Arrange>Break Apart Extrude Group command and then the Ungroup command.

These are the simple underlying principles behind extrusion but the idea can easily be taken further. In CorelDRAW this is done via the tabs via the dropdowns on the Extrusion tool's context-sensitive Property bar. To begin with, once created, you can use the proxy in the 3D Rotation dropdown to rotate your object in 3D space and so set it at any angle to the viewer. Using the Bevel dropdown you can also add a bevel - effectively you are creating another extrusion this time centred on the original shape and with a vanishing point in front of the object.

It's not just the extruded 3D object's geometry that can be controlled, you can also manage its formatting. Using the Extrude Colour dropdown, you can set the extruded face's colour to be the same as the front face, another colour or a gradient - the latter is particularly useful as it can give the effect of realistic shading. Greater shading control and so realism is available from the Lighting dropdown which lets you add up to three customizable lights that are positioned on a grid around the object and which then lighten the colours or gradients of those faces that would be illuminated.

Putting all this together, we can quickly create a rotated and beveled cube with gradient colouring and multiple lighting. And if we then break apart this advanced effect to see just how it is produced it turns out that all we are talking about are a few perspectivized and appropriately formatted faces. This shows the basis of the extrusion effect for the most basic shape of them all the rectangle/cube. Crucially, exactly the same principles can be applied to any other shape, the only difference being that curves must be broken down into short line segments that are then turned into perspectivized faces. The end results look smooth but, if broken apart, you'll see that for objects such as 3-dimensional text the number of individually formatted planes making up the effect quickly rises into the hundreds.

Extrusion effects are fundamentally simple but can be scaled up.

CorelDRAW's extrusion capability can be scaled up to produce some truly eye-catching three-dimensional effects, but again the basic functionality has changed little over the last fifteen years - so can the competition do any better? Until this year the answer was a resounding "no" as neither FreeHand nor Illustrator offered any extrusion capabilities, but in their latest MX and CS releases both packages have finally tackled 3D shape-handling head on.

FreeHand MX's new capabilities are immediately familiar taking the form of a Corel-style interactive Extrusion tool complete with a positionable vanishing point and a cross-bar for setting object depth. There are differences though such as the ability to directly rotate your new object in three-dimensional space. Using the Properties Inspector you then have fine control over your extrusion including the ability to set up shading. This is limited to two lights but, making up for this, is the ability to control the number of steps that determine the smoothness of the final extrusion so that you can rough out your effects quickly and then improve quality for final output.

The real advance that FreeHand MX provides is its ability to turn your starting shape into a whole host of new three-dimensional objects. This power is made available through the support for "profiles" which means that your extrusions no longer have to stretch in a straight line towards the vanishing point. By cutting and pasting an open path into the Inspector and selecting "Static" your shape will be automatically angled to follow the path. Even more powerful is the "Bevel" option which effectively uses the profile path as an extrusion envelope enabling you to create a huge range of symmetrical solid shapes such as vases and bottles. Sadly FreeHand's lack of advanced formatting control means that you can create the 3-dimensional shape but not make it look like a real world object.

FreeHand MX's extrusion profiles enable the creation of entirely new 3D shapes.

Illustrator CS takes a completely different approach to extrusion and 3D handling based on technology from Adobe's almost-forgotten vector 3D application, Dimensions. At first sight its new Extrude and Bevel command looks very like the 3D Rotate command that we saw earlier as the top of the dialog shares the same track-cube for rotating objects. Below this is the extrusion power with the ability to set the depth in points and choose from various bevel presets or use your own. Again perspective must be set as a lens setting so the lack of vanishing point support cuts down on interactivity and the ability to co-ordinate scenes. On the positive side the formatting control is more advanced with the ability to add any number of lights and minutely control their intensity, ambience and so on. And Illustrator CS also offers a "plastic" shading option that gives the object a reflective glossy appearance that can really bring it to life.

Like FreeHand MX, Illustrator CS also moves into completely new 3D territory in this case with its Revolve command. Using this you can create new three dimensional shapes by sweeping a closed path around the vertical y axis. To create a bottle for example you can simply draw one-side of it and then revolve the shape around either its left or right side. And because you can offset shapes you can not only create objects such as lamp bases but the lampshade itself. And you can still rotate the revolved object that you create in 3D space and shade it just as you can for extrusions. You can even choose to show hidden surfaces which is ideal for transparent objects such as our bottle.

Again though we hit the same problem that we did with FreeHand - creating the shape is one thing but making it look realistic and a believable part of a larger scene is another. Here Illustrator CS breaks important new ground with its surface mapping capability. This is available via the Map Art sub-dialog in both the Extrude and Bevel and Revolve dialogs and allows you to apply any previously saved symbol, including bitmaps, to the surfaces of your object. The mapping process isn't exactly simple, as you have to manually work your way through each surface and position each symbol, and it's particularly disappointing that there are no options for tiling symbols which would enable much more realistic texturing. However, the ability to customize even the curved faces of your object is a huge step forward.

Illustrator CS offers advanced 3D handling including revolving and surface mapping.

We've certainly come a long way. With Illustrator CS we now have the tools in place to see how our flat design would work as a label on a transparent wine bottle. With FreeHand MX meanwhile we have all that we need to create a realistic room and perspectivized table on which to put the bottle. Of course to be able to produce truly believable illustrations with real depth what we really want is the best of both approaches - and a lot more power besides. There's still a long way to go but things are certainly moving in the right direction - these days you don't necessarily need a dedicated 3D package to add an extra creative dimension to your work.

Tom Arah

January 2004

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