Tom Arah explores the ways in which 3D modelling and bitmap editing can be creatively fused.

The end quality of 3D output depends largely on the application’s handling of materials and, more often than not, this involves mapping imported bitmaps to your objects’ surfaces...

By placing a scanned label on the cylindrical surface of a generic glass bottle, for example, you can instantly turn it into a believable wine bottle while applying a seamless bitmap tile to create a brickwork pattern can instantly turn a flat plane into a realistic wall. Every 3D application relies heavily on such “texture mapping”, but few give it the focus and attention that it deserves. In fact, apart from basic controls over size, position and tiling, most applications provide little more than a generic Load Image command.

MAXON Cinema 4D

At first sight the PC Pro recommended MAXON Cinema 4D 10 (£499 + VAT, free trial available from www.maxon.net) looks fairly typical when it comes to bitmap handling in a 3D environment. The Material Editor’s main Colour channel offers a Texture parameter from where you can open a standard File Open dialog to load a bitmap from disk, optionally mixing this with a flat colour. The resulting material can then be applied to an object or a polygon selection by drag and drop which adds a texture tag to the object. It’s here in the texture tag settings that you can control offset and length and manage tiling. It’s also here that you choose the best projection method (cubic, spherical, cylindrical and so on) to determine how the flat 2D image should be wrapped around the 3D object to avoid visible seams and make the end effect look as natural as possible.

Cinema 4D’s bitmap handling looks fairly typical - at first sight

So far so-so. Look more deeply though and there’s some more impressive power on offer. To begin with, using Cinema 4D’s Content Browser, you can quickly create a catalog in which a folder’s bitmaps are displayed as thumbnails and can be dragged directly onto a blank space in the Material Editor to define a new material’s colour channel. You can also quickly drag your texture to other channels within the Material Editor and Cinema 4D supports texture mapping in no less than ten (diffusion, bump, reflection and so on). Click on the name of the applied texture in the Material Editor and you are taken to a sub-dialog where you can choose a layer from an imported PSD file (meaning that all of a material’s channel textures can be pooled in a single master file), set a sampling method and set the image’s exposure and black and white points to manage contrast.
More functionality comes from the ability to pre-process the bitmap using a range of dedicated shaders: Filter lets you manage hue, saturation, lightness, brightness, contrast, gamma and clipping; Colorizer lets you remap the bitmap’s colours via a gradient; and Posterizer cuts down the number of tonal levels in the image. A particularly important creative option comes from the Fusion shader which lets you combine multiple bitmap textures by managing transparency and blend mode. For maximum power the Layers shader provides all the above power with some other tricks of its own such as independent control over bitmap transforms and distortions. For hands-on interactive control of texture position, size and rotation Cinema 4D also provides dedicated Texture and Texture Axis tools.

BodyPaint 3D lets you paint directly onto 3D objects

MAXON BodyPaint 3D

On closer analysis Cinema 4D’s texture handling proves surprisingly powerful but it pales into insignificance compared to MAXON’s other major offering: BodyPaint 3D. BodyPaint 3D is designed to let you create dedicated texture maps tailored directly to the objects in your scene. More to the point it does so by fusing bitmap editing and 3D modelling in the most natural way possible – letting you paint directly onto your objects. It’s available as an add-on (£499 + VAT) designed to work with the four main professional 3D modelers: 3ds max, SoftImage XSI, Maya and Lightwave. Alternatively – and amazingly – with its last release, MAXON integrated BodyPaint 3D directly into Cinema 4D 10 without increasing its price and so effectively doubling its value.
So how does BodyPaint 3D work in practice? The easiest way to begin using BodyPaint 3D within Cinema 4D 10 is to switch the interface to the dedicated BP 3D Paint Layout which leaves the central scene window unchanged while, around it, a new dedicated toolbox opens to the left and control panels to the right. This dedicated BodyPaint environment certainly isn’t intuitive but find and click on the Paint Setup Wizard icon in the toolbox and you’re off. On the wizard’s first page select the objects or materials you want to work with, in the second UV Setup page choose either cubic or angle-based mapping and then in the final page set the material channels to create and the desired texture size (in most cases you can simply accept the defaults). Click on OK and, amazingly, you’ll find that you can now begin painting directly onto your object(s) within the 3D scene.
Painting like this feels liberatingly natural (simply hold down Alt to rotate the scene and continue painting your object in the round), but how does BodyPaint 3D make this magic possible? Behind the scenes, BodyPaint has created a new blank bitmap but, unlike the photos and tiles loaded from your hard disk that are wrapped around the object as best they can, this bitmap is broken down into separate areas that are accurately tied to the object’s polygonal mesh. In other words this is true texture mapping not just texture wrapping. To see exactly what this means, add an object such as a cone to your scene then run the Paint Setup Wizard and then switch from the default scene view to texture view and then in the UV Mesh menu switch on UV mesh display to see the grid. Effectively the object’s polygon mesh has been unwrapped and flattened onto the bitmap surface. As you paint on the 3D object. BodyPaint 3D maps your strokes to the flattened UV grid – or vice versa. Drag the Texture window next to the View window and you will see both update in real time as you paint.

Advanced BodyPaint 3D features include raybrush, multi-channel and projection painting

Mapping the object mesh to the UV bitmap is something of a dark art, particularly when it comes to curves and seams, and BodyPaint 3D provides plenty of options and tools for fine-tuning the process and results. However the real beauty of the program is that it generally hides these underlying technicalities and just lets you get on with painting. So what painting power is on offer? BodyPaint 3D offers various bitmap tools including fill, gradient, shape and retouching options, but the key tool is the hands-on, pressure-sensitive Brush. Switch to the Attributes panel’s Tool mode and you’ll see some impressive control over your brush starting with size, spacing, rotation and jitter. In addition you can specify a wide range of brush heads based on shapes, profiles and bitmaps and also apply a range of filters that affect how the paint laid down interacts with the paint already there. Put it all together and there’s a huge range of paint styles possible as shown in the dozens of provided presets arranged into categories such as charcoals, crayons, oils and acrylics.
It’s not just the control over brushes that is impressive. Switch to the Colour panel and you can specify your paint in a wide range of colour models. More importantly, you can also choose to paint with a bitmap rather than a single colour with BodyPaint automatically handling tiling. It’s relatively rare that real objects have a single flat colour so this “texture painting” is enormously important for bringing 3D models alive. And BodyPaint 3D makes it simple to scale, rotate and offset the texture to avoid seams as well as vary opacity and blend mode so that you can make the end result look as realistic as possible.
The direct hands-on painting that BodyPaint 3D offers is its greatest strength but it’s often preferable to hone in on an effect rather than immediately commit yourself. BodyPaint 3D enables this through its support for multiple layers. Using the Layers menu or panel you can add new layers, toggle their display, add layer masks and change opacity and blend mode. In addition BodyPaint provides various selection tools and supports third-party plug-ins so you can further explore the creative possibilities of multiple overlays much as you would do in Photoshop.
BodyPaint 3D’s 2D painting credentials are impressive but its 3D power is extraordinary. Particularly striking here is the ability to paint to multiple channels simultaneously so that, with both colour and bump channels specified for example, you can immediately create a wall in which the bricks seem to stick out beyond their cement. With its “raybrush” mode you can even paint like this directly onto a rendered version of the scene, say to apply weathering and dirt. Most useful of all is BodyPaint 3D’s Projection Paint capability. Using this you can paint on the current view as if it was flat and BodyPaint will then project the paint onto the underlying UV grid. You can also project existing bitmaps in this way so that you can project a photo of a face onto a model, for example, and then use BodyPaint 3D’s hands-on painting to fine-tune the results.

Piranesi’s depth support enables interactive rendering

Informatix Piranesi

BodyPaint’s 3D painting capabilities are extraordinary – but it’s primarily a tool for modelers rather than artists. Another exceptional program merges 3D and bitmap functionality to offer hands-on 3D painting but does so while always keeping the focus on artistic creativity. Piranesi 5 (£395 + VAT, free trial available from www.informatix.co.uk) is a paint program with a difference. Rather than handling typical bitmaps which work with colour information stored in RGB channels, Piranesi uses its own Extended Pixel (EPix) bitmap format which also stores channels for depth and material information.
This means that, before you can do anything with Piranesi, you need an EPix file to work with. For most major professional applications that shouldn’t be a problem as many, such as VectorWorks, Vue 6 Infinite and SketchUp Professional, provide native export while Informatix provides rendering plug-ins for 3ds max, LightWave and Cinema 4D. Alternatively, you can export a simple 3DS version of your object or scene and then load it into the separate Vedute utility bundled with Piranesi which lets you set up your view and lighting before exporting to EPix. In the latest Piranesi release, Vedute 5 now supports textured objects but previously all textures where rendered as white which might sound like a pretty catastrophic drawback. In fact it’s not as that extra depth and material information in the EPix file makes it simple to use the main Piranesi application to “interactively render” your scene from scratch.
Key to this capability are Piranesi’s support for locks and texture wrapping. Simply select the Fill tool and switch on the material lock and you can quickly apply paint to the whole material under the point where you click – the area is automatically masked. As I’ve said, flat colours are actually relatively rare which is where Piranesi’s texture handling comes in. Select the Texture checkbox on the main Tool Options bar and click on the down arrow next to it and you can select from a wide range of pre-provided textures arranged into categories such as stone, vegetation, wood and so on. Make sure that the mode is set to Auto Tangent or Auto Wrapped in the Advanced Settings panel and click on your object and the seamlessly tiled texture doesn’t just uniformly fill the space; it honours perspective, changing size and angle, and smoothly flows over the material’s surface! Just like first painting with BodyPaint it’s one of those jaw-dropping moments that seems so extraordinary just because it feels so natural – and again the apparently effortless magic is only possible thanks to a great deal of behind-the-scenes processing, in this case of each pixel’s underlying depth information.

Piranesi’s main focus is on 3D art

Often the immediate results are all that you need especially as the provided textures are automatically scaled for correct use. More often though, you’ll want to fine-tune the results, for example changing the texture size or varying the mix between the texture and the current colour. Often you’ll also want to overlay multiple textures say to apply weathering to a brick wall. Piranesi doesn’t offer a Body Paint-style layering system to enable such control over effects, but it more than compensates with its ability to retrospectively fine-tune your last action by changing settings and then hitting the ReApply command (shortcut Ctrl+R). Using the Tweak command you can even reposition, resize and rotate the current texture directly on the object itself. And with the ability to vary transparency and blend mode (crucial to preserving existing shading) and to apply multiple fills, it’s possible to quickly build up rich texturing in real-time – an absolute pleasure compared to the typical laborious and hands-off material handling seen in most 3D applications.
Piranesi’s interactive handling of global texture fills stands out but, as we saw with BodyPaint 3D, real creative flexibility comes from local hands-on painting. The latest Piranesi 5 offers an enhanced Pencil tool for laying down lines and shapes but again the key is the freehand Brush tool. Here Piranesi offers reasonable control over the brush style with four main types to choose between - circular, rectangular, bristle and bitmap - and control over size, angle and spacing and the ability to vary colour, position, size and angle dynamically. It also offers full control over paint mixing as well as the ability to add a canvas-style grain and to control opacity and blend mode. And you can also change settings and reapply your last brush stroke to get absolutely the result you want – now why can’t Photoshop do that?
Working like this, Piranesi feels like a traditional responsive 2D painting application, but that extra material and depth information enables Piranesi to offer a lot more. As well as material locking you can automatically limit your paint strokes to particular planes and/or colours which, taken together, makes a huge and liberating difference – no more going over the lines of your objects (unless of course that is the effect you are looking for). You can also interactively paint with seamless textures that automatically flow over your scene’s surfaces. Crucially you can also toggle the brush head so that it orients itself to the underlying geometry to produce strokes that automatically honour your scene’s perspective and geometry.
The Brush moves on dramatically from the Fill tool but it proves to be just the start of Piranesi’s power. Alongside the Brush tool, Piranesi 5 now provides a Stamp tool which lets you paint multiple bitmaps onto your scene, very useful, for example, to paint ivy on a wall. The Painter tool also lets you load multiple bitmaps as brush marks but here you specify the paint that the tool lays down so you can create an artistic interpretation of the current texture or a stored version of the scene – there’s even a Splatter option complete with depth sort so that you can automatically create an artistic hand-painted clone of your 3D scene. And with the Edge tool you can limit the effect of your strokes to the material, depth or colour edges in your image, while with the Filter tool you can interactively apply effects some of which, such as the halftoning effect, pick up on and highlight the underlying geometry

Put it all together and Piranesi really does offer some uniquely powerful and excitingly creative new 3D painting power – but it’s worth remembering its limitations. To begin with it’s important to remember that you are working with static renders – the 3D nature of the image within Piranesi is so strong that often you want to just rotate the current view a bit but of course that’s just not possible without going back to the original 3D scene and re-rendering. For the same reason animations are out of the question. Moreover, while you can use Piranesi to add even greater depth to photo-realistic renders – say adding the grime and weathering that really brings a clearly computerised render to believable life – you can’t build up truly photo-realistic images from scratch. True photorealism depends on the rendered interplay of light between the different material channels – bump, reflection and so on – but Piranesi is effectively only working in the colour channel.
Of course it’s in precisely this area of complete integration with the modelling and material rendering of the originating 3D application that BodyPaint 3D excels. So you have two excellent choices. If you’re more interested in photo-realism and the 3D potential of your work then BodyPaint 3D is the right option; if you’re more interested in painting and the creative potential of your work then it has to be Piranesi. In both cases the power on offer is extraordinary - as is the way that the complex bridging of two very different words is made so completely natural that you can simply pick up a brush and begin painting.
If you want the absolute best of both 3D painting approaches that’s possible too: just make sure that your 3D modeller supports both BodyPaint 3D and Piranesi with Cinema 4D 10 being the obvious first choice.