3D-Coat vs. ZBrush auto-retopology comparison

11 February 2018

I love the technique of freeform digital sculpting, as an alternative to polygon subdivision modeling. The workflow of digital sculpting feels very much like traditional sculpting, adding daubs of digital clay and dynamically shaping them into a sculpture, while polygon subdivision modeling requires careful construction and adjustment of a quadrangular polygon cage in order to successfully subdivide it to a smooth result. This quad-polygon structuring and restructuring can be time-consuming and sometimes frustrating, and often takes away the spontaneous part of 3D model creation.

A downside of freeform digital sculpting is that it usually results in a messy polygon structure, making the 3D model unsuitable for deformation, such as for posing or animating a character. But even if no posing or animation is required, the semi-random polygon structure often causes visible surface irregularities, especially if you sculpt with triangular polygons, like when using Blender 3D's Dyntopo sculpting. Dyntopo is short for dynamic topology, and I love to use it for conceptual sculpting, as polygons are generated in realtime while you sculpt, enabling you to freely focus on shaping your model without having to worry about its polygon structure.

Triangles and quadrangles

A smooth 3D surface impression can be achieved by either a smoothly flowing quadrangular polygon structure or a high polygon count (or both). A smooth polygon flow is usually realized by constructing rows and columns (rings and loops) of quadrangular polygons that fluidly follow the flow of the 3D shapes (convex and concave areas, creases and other surface features).

For the best of both worlds, many 3D modelers manually retopologize their models when the freeform sculpting is finished, restructuring the surface to a smooth quad-polygon result. But manual retopology still requires careful planning and patience as you place the quads across your sculpted surface. It can be a tedious, time-consuming and sometimes puzzling process.

Automatic retopology tools

At the time I write this, the most popular 3D sculpting tools are Blender 3D, Pilgway's 3D-Coat, and Pixologic's ZBrush. To ease the process of retopology, 3D-Coat and ZBrush offer a way to automatically generate a nicely flowing all-quad surface for your sculpture. 3D-Coat's auto-retopology tool is called Autopo, and ZBrush features ZRemesher.

There is another automatic retopology tool. It's called Instant Meshes, and deserves an honourable mention. Instant Meshes is fast and free, but did not make it into this test, because it generates too many triangular dead-ends amidst the resulting quad-polygons, resulting in visible artifacts after subdivision. The Instant Meshes quad-retopology algorithm or a variation is used by The Foundry's Modo.

Blender 3D does not yet include an automatic quad-retopology function, only a generic, voxel-based quad-poly projection method in the shape of the Remesh modifier, which doesn't orient the polygon flow to the surface features.

3D-Coat Autopo versus ZBrush ZRemesher

After speed-sculpting the above-pictured happy dog I decided to do a little test to get an impression which auto-retopology tool yields the most satisfactory out-of-the-box result, 3D-Coat's Autopo or ZBrush's ZRemesher.

I used 3D-Coat version 4.8, and ZBrush 4R8. Symmetry was activated in both tools, and no changes were made to the default settings, with two exceptions:

1 — ZRemesher's Adaptive option was deactivated, to force the resulting polygon amount more to the Target Polygons Count value.

2 — Autopo's Required Polygon Count was doubled from 5000 to 10000, because that made the resulting polygon amount comparable to a ZRemesher Target Polygon Count value of 5, which should equal 5000 polygons, but the resulting amount of polygons still deviated somewhat from that number.

ZRemesher offers two different auto-retopology algorithms. You can apply the alternative method by holding the Alt key while activating ZRemesher.

The Autopo algorithm and ZRemesher's algorithms take a similar amount of calculation time, depending on your computing capacity and the model's complexity. Usually the calculation takes less than 30 seconds for a model of average complexity, up to a few minutes for a more complex model.

Angled view

As you can see, the results with the applied near-default settings are quite similar at first sight. All three algorithms result in a neatly distributed, fully quadrangular topology and a smooth edge loop flow along the 3D model's curvature.

Looking at the dog's face, my personal preference goes to 3D-Coat's Autopo result. Particularly the eyes are surrounded by nicely distributed, smooth edge loops, while both ZRemesher results are a bit cluttered around the eyes, resulting in some tension and edge loop spiralling there.

Front view

Switching to the front view, you can see that both ZRemesher algorithms kept the eyebrow area more defined than Autopo. On the other hand, the edge loop flow in the mouth's corner cavity areas is slightly better in the Autopo result.

Side view

Looking at the side view, many similarities are visible between the Autopo algorithm and ZRemesher's alternative algorithm, but Autopo is the only method with an uninterrupted edge flow along the tail.

It looks like the standard ZRemesher algorithm has resulted in a considerably higher polygon count than the other two methods, but the polygon amounts don't differ that much. It's mainly a matter of varying polygon distribution across surface features. For example, the dog's nose in the Autopo result has more polygon density than the ZRemesher versions.

Before and after

To emphasize the difference between the initial and the final model, here's an impression of the rough Blender Dyntopo speed-sculpture next to the 3D-Coat auto-retopologized, subdivided and smooth-shaded model. I chose the Autopo result, because I personally liked that just a bit more than ZRemesher's results, using this test's near-default settings.

Final notes and advice

Some final notes and advice to conclude this simple auto-retopology test:

• Please note that the results of this test are based on only minimally adjusted default settings of 3D-Coat's Autopo and ZBrush's ZRemesher. Both auto-retopology tools offer a number of powerful options to influence the result, such as polygon density painting and placement of curves to guide the topology flow.

• It's also worth noting that this test features a regular, organic 3D model with a smooth curvature. Meshes with certain features, such as hard-surface models featuring sharp angles, and meshes that have thin walls are often a harder nut to crack for auto-retopo algorithms. In other words: auto-retopology tools are not foolproof yet.

• To my personal experience, indicating areas of varying polygon density and/or adding curves to guide the topology flow should be done with care, because it complicates the task of the auto-retopology algorithm. It's then forced to find new ways of solving the quad-topology flow in specified areas, which can cause topology degradation in other areas. My advice is to always first try auto-retopology without any manual interference, and only add guidance if it's really necessary.

• Try to make use of symmetry whenever possible. It eases the auto-retopology algorithm's task by only having to process half of the model, and enables an edge loop corridor across the symmetry axis.

• Always try to keep your retopology polygon count as low as possible. In case of detail loss, subdivide the retopologized result and use the original high-poly model to reproject details onto the retopologized model.

• I've found that a mesh with triangular polygons often works better as input for auto-retopology than a quad-based mesh. Maybe it's easier for the algorithms to process the generic flow of a triangular surface, which also usually has fewer polygons than a quad-based mesh. You can decimate and/or triangulate your input mesh before applying auto-retopology.

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— Metin Seven, metinseven.com

Angry mech — vector style exercise

05 February 2018

Whenever I'm not 3D sculpting I love to relax by creating freestyle 2D graphics, fiddling around until I've established something satisfactory.

Today I cooked up this angry mech. Don't mess with this fellow!

If you really like this image, it's available as a print on all kinds of items in my Society6 store, alongside many of my other works.

You can like my blog posts or leave a comment at Artstation.

Game Boy — vector and pixel artwork

02 February 2018

I love retro games, as you might have noticed by the amount of retro game themed artwork in my portfolio. 🙂

My latest tribute to the exciting dawn of the digital revolution is an imaginary Game Boy game mockup, attempting to recreate the old screen characteristics.

Here's my original pixel art sketch that served as the basis for the vector version:

If you really like this image, it's available as a print on all kinds of items in my Society6 store, alongside many of my other images.

You can like my blog posts or leave a comment at Artstation.

Lost in space — cartoony vector illustration

16 January 2018

An unfortunate space adventurer, forever lost in space after being disconnected from his spacecraft. 💀

In case you're wondering how this was realised — I've explained my workflow for this kind of artwork in the previous blog post.

If you really like this image, it's available as a print on all kinds of items in my Society6 store, alongside many of my other images.

You can like my blog posts or leave a comment at Artstation.

Skull collector — vector artwork

12 January 2018

People who've seen my work often have the preconception that I'm solely creating 3D artwork, but nothing could be further from the truth. I love to create 2D character designs and artwork as well. In fact, when I was a young bloke I started my career as a 2D pixel artist for 16-bit games (Commodore Amiga, MS-DOS and Windows). Hence my fondness of low-resolution pixel artwork, which I regard as a distinctive form of graphic design, simplifying shapes and colors to the pure essence.

When I create vector artwork, I try to translate the iconic characteristics of low-res pixel art to vector shapes. My workflow for this is to start by sketching the image as actual pixel art.

Then I enlarge the pixel art and trace the shapes in Affinity Designer. Affinity Designer doesn't contain an automatic bitmap to vector conversion tool at the time I write this though (I'm using version 1.6), in case you're looking for that. Up to now I haven't found a really effective low-res pixel art to vector conversion tool, and I hope the AI / machine learning revolution will soon change that.

After creating the vector version, I like to add a little soul to the sterile geometric shapes by post-processing the artwork in an image editor, adjusting colors, adding noise, etcetera. Below you can view the final result.

If you really like this demonic skull collector, it's available as a print on all kinds of items in my Society6 store, alongside many of my other images.

You can like my blog posts or leave a comment at Artstation.

Making of De Ruyter 3D print model

06 January 2018

The talented cartoonist and comic strip artist Pieter Hogenbirk is a good old friend of mine. One of his comic strip series is based on a famous Dutch historical figure: admiral Michiel De Ruyter (1607 - 1676).

To practice 3D sculpting with Pixologic ZBrush, I offered Pieter to create a 3D-printed bust of De Ruyter, so he could have a tangible version of his character on his desk. Pieter responded enthusiastically, so I rolled up my sleeves and started.

Usually, the first stage is gathering reference images. I collected some comic panels from De Ruyter for an impression of the characteristics. Then I started to build a very elementary model, consisting of basic 3D shapes.

During the second phase I combined the basic shapes into one 3D model using the Dynamesh tool in ZBrush, and added the head's major elements: eyes, hair and moustache. I also assigned some colors, to get rid of the red clay look, and make the character more lively.

After showing the first result to Pieter, he clarified that the apparent tuft on top of the character's hair is actually his hair parting. So I corrected that.

While refining the head, I decided to choose shades of gray in stead of cartoony colors, going for a classic stone-like look, as the final bust would be printed in a sandstone-ish material, and colors can sometimes distract from forms, especially when the colors are saturated.

Once the head was more or less finished, the chest was sculpted, cutting off angled regions in classic bust tradition.

During the last sculpting stage, clothing accessories and a classic-style pedestal were added.

After uploading the final, hollowed-out 3D model to my Shapeways 3D print store, I created an impression using the Keyshot renderer.

And here are two photographs of the final sandstone 3D print. Some of the definition was lost due to the limited resolution of the 3D printer.

In conclusion, I really enjoyed sculpting the figure. The biggest challenge was successfully translating the very stylized 2D drawings to 3D shapes while trying to keep the characteristics intact from every angle.

You can like my blog posts or leave a comment at Artstation.

Necronaut — low-polygon 3D artwork

03 January 2018

Allow me to introduce you to Necronaut. What better way to start a new year than by creating some gloomy sci-fi horror. 😉 

I love the iconic, graphic nature of low-polygon 3D, and the dramatic lighting contrast you can achieve with it. I restricted myself to polygon angles of 45 degrees for a robust Art Deco style result.

Here's an impression of the untextured scene in the realtime viewport of Blender (2.79), my 3D editor of choice for this work. I love Blender's versatility.

For the final image I tried to achieve a nice blend of stylized shapes and a grungy, textured finish, to avoid a result that is too sterile. Part of the texturing was rendered on the surfaces, and a subtle second layer of textures was added in the post-production phase.

Post-production was performed using Photoscape X, a gem of an image editor. It's available for both MacOS and Windows. The free version already offers a lot of functionality, but I recommend buying the Pro version (an in-app purchase for MacOS). It's worth the affordable investment, and you'll support a dedicated developer. Don't worry, I'm not being paid to mention this. 😉

If you really like this unfortunate space adventurer, it's available as a print on all kinds of items in my Society6 store, alongside many of my other images.

You can like this blog post or leave a comment at Artstation.

Happy Holidays — isometric pixel art

23 December 2017

Happy Holidays!

Here's Santa's all-new artificially intelligent factory:

After creating the illustration in isometric pixel art style, I decided to convert it to vector graphics, and liked that just a little bit more:

You can like this blog post or leave a comment at Artstation.