Blender 3D auto-retopology add-ons

Article / 28 October 2018

Some time ago I wrote this article about automatic polygon retopology tools, comparing the Autopo auto-retopologizer in 3D-Coat to the ZRemesher auto-retopologizer in ZBrush.

As I love to use Blender 3D alongside ZBrush, I've been waiting for a decent auto-retopology tool inside Blender for a long time now. Blender 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, and usually results in artifacts when the result is subdivided. The Remesh modifier could be compared to the old Remesh All tool in ZBrush, which is generally inferior to what might be called its successor in Zbrush: Dynamesh, and more inferior to the impressive ZRemesher auto-retopology tool in ZBrush.

Recently, two very affordable auto-retopology add-ons have been released for Blender: DynRemesh and Tesselator, also called Particle Remesh. I bought both of them and performed a quick 'n' simple test. Both add-ons are easy to install, and after installation the options are available in Blender's Tool shelf at the left side of the user interface.

For the test I used Blender's Suzanne monkey mascot, but deleted the separate eyes of the model, and closed the eye sockets using the Grid Fill tool in Edit Mode, to form a watertight, manifold mesh for the test. Then I subdivided the mesh a couple of times, to smooth the surface. I didn't change the default settings of both add-ons. I used DynRemesh version 1.5, and Tesselator / Particle Remesh version 1.0.

The screenshot's top row shows the results, while the bottom row has subdivision added to the results.

As you can see, both add-ons result in fully quadrangular topology. If you focus on an even topology distribution, Tesselator / Particle Remesh seems to be the best of the two Blender solutions, with a result that comes close to the Instant Meshes auto-retopology algorithm. Tesselator / Particle Remesh uses its own proprietary, particle-based auto-retopology algorithm, while DynRemesh is essentially an automated combination of native Blender modifiers and tools under the hood.

Both solutions show topology artifacts in different areas after subdivision, if you look at the bottom two versions of Suzanne. This is caused by three topological factors:

  1. The amount of five-sided, six-sided and sometimes even seven-sided or eight-sided singularities: multi-edge junctions that form a star-shaped knot, sharing the same center vertex. These multi-sided singularities become visible artifacts when subdivided because they interrupt the flow of edge loops / quad-polygon loops.
  2. The positioning of multi-sided singularities. When placed at strategic surface locations, singularities can become less visible.
  3. Surface curvature versus edge loop flow / quadrangular polygon loop flow. The more edge loops follow changes in the surface curvature of a mesh, the smoother the subdivided result will be.

Dynremesh shows a rather distorted topology distribution in some areas, but other areas are looking better when subdivided than the Tesselator / Particle Remesh result, such as the surrounding edges of the eye sockets, while Tesselator / Particle Remesh performs better in preserving the shape of the mouth.

In conclusion, these Blender add-ons don't yield the sophisticated results of 3D-Coat Autopo or ZBrush ZRemesher, but those are comparatively expensive commercial tools. In my personal opinion, Tesselator / Particle Remesh is currently the best choice for auto-retopology inside Blender. At the time I write this it has a lower price than DynRemesh, and the current Tesselator / Particle Remesh version 1.0 features more useful additional options than DynRemesh version 1.5, such as being able to use Grease Pencil strokes to guide the auto-retopology process.

Last but not least, I hope someone will soon release a usable implementation of the Quadriflow algorithm, which is an improved version of the above-mentioned Instant Meshes auto-retopology method.

— Metin Seven (

Moon Child — free platform game for iOS, macOS and Windows

Article / 21 July 2018

In a distant, fondly remembered past I was a full-time designer and graphic artist for 16-bit games. Together with two partners — coder Reinier van Vliet and music composer Ramon Braumuller — I developed commercial games for the Commodore Amiga, CD32 console, MS-DOS and Windows, among other platforms.

One of our biggest game projects was Moon Child, a platform game we initiated for the AGA (Advanced Graphics Architecture) generation of Amiga computers, but then Commodore sadly went down in 1994, and we were forced to reinitiate Moon Child game development for Windows, which by that time turned out to allow higher resolution graphics and better audio than the previously superior Amiga.

Moon Child was published back in 1997. Years later we decided to release the game as a free download. The original Moon Child Windows CD-ROM and a few of our other games can be found at the Internet Archive, but Moon Child is also available as a free iOS game (iPhone / iPad) and a free macOS game.

More info about our Amiga games can be found in the Hall Of Light database.

I hope you have as much fun playing the game as we had creating it!

Films, my passionate pastime

Article / 02 March 2018

When I'm not busy creating imagery, one of my favourite pastimes is watching films, and writing short impressions of them on Letterboxd.

I consider film to be the ultimate form of expression, combining visuals, audio and motion to tell a story and convey emotions. It's like traveling to an alternate reality for a few hours, if the film is convincing enough.

Letterboxd is a great platform to create your own film journal, allowing you to express whatever you like about the films you've seen, including reviews, ratings and lists.

Here's my current film top 25:

As you can see, I tend to prefer dark, moody and often surreal films. I think those films offer the most interesting escape from the sometimes unbearable dullness of reality.

The Shining is my all-time favorite film. Stanley Kubrick delivered an audiovisual masterpiece in 1980, making effective use of state-of-the-art camera techniques. The estranging symmetry of the shots, the 1970s carpet and wallpaper designs, the "All work and no play..." scenes, Jack Nicholson's progress from sanity to insanity, and so on. Every time I watch The Shining, I recognize more of its magnificence.

You're invited to have a look at my full list of favourite films, and my hundreds of short movie reviews. I hope you'll discover a few gems.

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

3D-Coat vs. ZBrush auto-retopology comparison

Article / 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.

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

— Metin Seven,