VFX workflows – Part 01

Escape VFX tutor Carlos Poon talks through ZBrush and its role in the VFX Pipeline at Escape:

In this series we will be discussing workflows created by our VFX students. We will start with ZBrush and how it can be used within our VFX pipeline. With so many tutorials available, it is often hard to find any explanations as to why you might use a particular tool, and which software features are appropriate for your modelling task. In this article we hope to give you an overview that helps you to understand the possible workflows used by Escape VFX students.

How can we use Zbrush?

ZBrush is a 3D sculpting application which is very versatile and has an endless list of features, so it can be difficult to know where to start. You might start with a 3D model in Maya and take it into ZBrush to add displacement detailing, or you might start concepting your ideas in ZBrush and then retopologize your sculpture into a clean model that can be used in Maya. With both workflows, your model will need UVs to map the displacement details that you create in Zbrush on to your 3D model.

If you start in Maya with a model that has UVs, you can export this ready for use in your sculpting software. Once in Zbrush you can import your Maya model, and start adding small surface details that are impossible to model in Maya. Examples of this might be folds and creases in clothing, scales on a dragon’s skin, or wrinkles on a character’s face.

ZBrush is a very capable sculpting application that is perfect for creating sculpts of organic things like human characters and creatures, or environment assets like rocks and tree trunks. ZBrush also has tools which allow for hard surface modelling of things like weapons and vehicles. If you wish to make something with a very complex curved surface you can use the sculpting tools to create curved surfaces, and then retopologize them into a clean mesh with a sensibly spaced and distributed polygons. Zbrush has a tool called ZRemesher which can create clean polygon models from your sculpts, or you could export your sculpt into Maya, and use the ‘Quad Draw’ tool to create a polygon mesh that would be more suited to animation deformations. Maya’s ‘Quad Draw’ tool allows you to do a manual retopology process, so that you can choose the size, spacing and edge flow for your polygon model.

So many tools, where do I start?

ZBrush has so many tools it can be difficult to know where to start. If you are working on a creature concept, you will probably have lots of ideas that change quickly, so you will want to be able to capture those ideas as quickly as possible, and start working on variations. Within ZBrush, a good place to start is with the ZSpheres feature. ZSpheres allow you to quickly sketch by moving spheres around to create shoulders, elbows and wrist joints. You can also block out forms like the torso and head. When you are happy with the overall shape and position of all your ZSpheres, it is very easy to create a skin which wraps itself around all of the spheres to create an ‘Adaptive Skin’. This skin is the perfect base to continue work in Zbrush, adding more sculpting details to your base form.

I have a 7 million polygon sculpt – how can I use this?

So you have finished creating you sculpt in ZBrush, it looks great, lots of sculpted details and when you go close you can see all the tiny scratches and surface noise that you created, and you try to export your model to Maya. You now have a 7 million polygon model and you can’t rotate your viewport because the model is so heavy; you can’t even see through the wireframe, as it is so dense, you have so many polygons.

This is not the way to work, it is impossible. The idea behind it all is that we use a clean base mesh, with a reasonable number of polygons to work with in our view point, and then we use a displacement map to hold all of the heavy surface details, and display them at render time. That is the whole idea behind it all, we use ZBush in this case for detailing the small difficult to model features, we export these details into a black and white texture map, and we displace our models surface at render time.

There are so many software tools, is is often hard to know where to start, which software to use, which software features are suitable for what you want to create. When working by yourself on your own projects, this is not so much of an issue, but when working with other people within a VFX pipeline, exporting your models and passing your work on to other members of your team needs to be standardised. In future posts, we can continue to explore this interoperability and suitable workflows to help you work within industry teams.

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