# 3D Character Modelling – ZBrush love

June 15, 2010

3D polygonal modelling tools for making complex organic forms have developed rapidly in the last few years. Traditionally the process has been to work step by step from platonic geometric primitives like planes, cubes, spheres, tori, cylinders etc. Modifying these by a number of discrete processes one after another. These are essentially mathematical geometric operations like scale, translate, rotate, extrude, divide, chamfer, bevel, etc… These methods have evolved from mathematical modelling methods and are in part a legacy of needing to be geometrically efficient during a period when computers were not very powerful.

These methods are very good for producing simple forms in an efficient way. Like buildings, props and environmental features.

For more complex and detailed forms, better methods of modelling have recently evolved, developing out of rendering methodologies and concepts. It takes a a bit of a conceptual shift when you first approach the method but quickly becomes natural. ZBrush, Mudbox, and Modo use such concepts. Zbrush was the first, and the most highly developed of this kind. When it appeared a few years ago represented a breakthrough in polygon modelling complex and organic forms.

Essentially the ZBrush method works like a live displacement map. The method requires working on one single coherent piece of geometry at a time. The ‘Z’ dimension is controlled by the alpha stamp of a brush, and is set in relation to either the origin of the geometry or the view point of the working window.

Deformations are applied to vertices of a base geometry by applying a grayscale value from an alpha map whose colour value is used to calculate the distance the vertices are translated. This happens in real time and the method makes it possible to do very sensitive modelling. The alpha values are modified by pen pressure and depth thresholds can be set as you want it. Other brush controls alter the tangent of vertex translation, and or can offset their effects tangentially from the origin. Additionally, any alpha map can be used for the brush stamp. These effectors can be combined and tweaked to achieve almost any localized surface modelling operation imaginable.

The ZBrush workflow starts with a low resolution base mesh. This can be a simple model imported from another polygon modelling package. Or another ZBrush specific method called Zspheres. Zspheres essentially uses joints and bones as geometry generators. This has the benefit of generating geometry with a topology that matches the layout of the joints, which means the edge loops always fall in the right places for animation. The mesh can be subdivided through stages and edited at each subdivision level. It can divide to the point where there are millions or even billions of polygons. This level of resolution means the surface can contain extremely fine detail.

Obviously a massive geometric model would be impossible to animate. The fine detail is stored and baked out by Zbrush as a displacement map that can be re applied at render time in Maya, 3DSMax, etc.

Composite models are achieved by creating ‘sub tools’, these are basically separate meshes that exist in a grouped hierarchy. ZBrush has an extract function that generates a new closed piece of geometry from a masked part of an original mesh. This is very useful for modelling difficult items in relation to the original, e.g. When making clothes that are fitted to a human character, it is possible to select the torso and arms, then extract a mesh that is the same shape and has the same number of points as the area it is covering. It is then a simple matter of modelling the new geometry into a form that is correct for clothing.

A great advantage of this is that it opens up several ways of saving time and labour in later animation processes. It is possible to reuse generic base meshes, using the same starting point for multiple characters. Then, because the meshes all have the same vertex number in the same numerical point order. It is possible to create an animation rig for the first mesh that can be applied to the subsequent meshes with little modification. With the proviso that none of the base geometry is added to or taken away.

The current version 3.5 has been refined improved and given a host of extremely well thought out digital tools. with particular attention to the character design workflow in particular E.g. UV mapping takes seconds, colour and textures can be painted directly onto models

It is genuinely a pleasure to use.

The development philosophy for the tools within zBrush has been to observe traditional manual artistic skills being used by skilled sculptors and create systems that allow artists and designers to work without too much interference from the functioning of the software. Attempts have been made with some success to make analogous tools that mimic traditional artists practices.

I noted in a previous report that much of the mental effort involved in ‘making’ 3D objects on screen is in holding the object in mind, whilst switching attention to the operations you want to apply to he form. In direct response to observing the way in which artists work, the interface is designed to create a working environment that is sympathetic to the quality of attention that is needed to produce highly detailed and complex models.The design of the interface avoids context shifts, unless they are strictly necessary, in order to prevent distraction of the artist’s attention from the model they are working on. This means that a lot of the specialized functionality is hidden away and requires background research to find it and understand it. Fortunately, Pixologic have produced a good user support model that provides this information that is based upon user forums and they pay advanced users to make tutorials that are available online. The clarity of the documentation produced this way is impressive and easy to access.The interface design makes it very conducive to the use traditional hand drawing and sculpture skills. The software entirely depends upon using graphics tablets or Cintiq style screens, which are the tools that allow the easiest translation of hand skills to the screen. The modelling workflow mimics traditional sculpture workshop practices in many ways. Overall the way of modelling with ZBrush allows the artist designer to keep attention on the visual issues of the task in hand. When working attentively, I found that perceptually the interface almost disappeared. As an experienced sculptor the drawing and translating of observational resources was almost identical to working withmaterial. Except that you can undo you errors with a button click. This is an area that deserves further research.

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