Toy robot promotional gift design

General / 08 November 2018

Some time ago I created a 3D robot design, which was spotted by a client who asked me to turn it into a toy robot design for a promotional gift.

This is the original design:

And this is the adjusted plastic promotional gift variant:

As you can see I’ve added the company logo, adjusted the legs to better match the arms, and to be robust enough for a small plastic figurine. I also removed the antennae to make the figurine a little more compact, and added teeth for a nicer smile.

Because the company develops drone control software the robot should be able to fly, but propellors didn't really work, so I added a jetpack.

The amount of colors was reduced to only two shades of blue, because each extra color raises the price of the final product.

Blender 3D tip — Realistic Specular value in Principled shader

Tutorial / 02 November 2018

I love Blender 3D. It's a deservedly popular and successful open source 3D editor. Together with ZBrush it's my most important tool for 3D creation. Since version 2.79, Blender's Cycles renderer includes the Principled shader, enabling you to create most material types using a single shader node. I'm happy to share a little tip for a slightly more realistic result.

The reflectivity of a material created with the Principled shader node is usually a balance between three values: Specular, Roughness and IOR. IOR is an abbreviation of Index Of Refraction, and indicates how much light rays are bent when they are reflected or refracted.

Every material has an average IOR value. For really accurate results each light wavelength reflecting from or refracting through a real-world material has its own IOR value, but an average IOR value usually suffices in the world of 3D.

Higher IOR values increase the light bending effect. In the case of reflections, this causes a surface to generally become more reflective. For example, shiny metals usually have a higher average IOR value than plastics.

A great online resource of IOR values for all kinds of materials is the IOR List at Pixel and Poly.

The Specular value of Blender's Principled shader is usually left at the default generic value of 0.5, but for a more realistic result there's a formula to convert a material's IOR value to the corresponding Specular value:

Specular = ( ( IOR − 1 ) / ( IOR + 1 ) ) ² / 0.08

Some examples, applying this formula:

  • Water: IOR = 1.33, Specular value = 0.25
  • Glass: IOR = 1.5, Specular value = 0.5
  • Diamond: IOR = 2.417, Specular value = 2.15

To automate this formula for the Principled shader I've made a little node setup that processes an IOR input value to the correct Specular value:

As shown in the screenshot:

  1. Group the formula node setup to a single group node with a value input slot, and label it 'IOR to Specular'.
  2. Connect the IOR to Specular formula node group to the Principled shader's Specular input slot.
  3. Connect an Input ➔ Value node to both the node group's input slot and the Principled shader's IOR input slot. For clarity, enter 'IOR' as the Value input node's label.

For clarity: this node setup translates a material's IOR value to the Principled shader's Specular value, while the Principled shader's own IOR value only applies to refraction (the Transmission setting in the shader), but it's convenient to already plug the IOR value into the IOR slot as well, in case you want to add refraction (Transmission).

Now all you have to do is look up the correct IOR value for each of your materials and enter that in the IOR Value input node. Note that you'll still need to adjust the Roughness value, but this node setup adds a little bit of realism to the Principled shader.

Below you can see two test renderings I made using Blender's Suzanne test-monkey, with a Roughness value of 0.5. As you can see, the interaction between the IOR value and the Specular value causes a sheen of specularity to appear, without using the Principled shader's Metallic or Sheen option.

I hope this helps you achieve slightly more realistic renderings!

— Metin Seven,

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 (

Love hurts

General / 02 October 2018

I found this old scribble in my ar(t)chive. I still like the concept.

Mickey the Poo

General / 25 September 2018

Mickey the Poo. 💩

Retro electronic music maker — vector illustration

General / 23 September 2018

Vector illustration of a retro electronic music maker.

Tiger toy figure model — Work In Progress

General / 19 September 2018

Three stages of modeling a tiger toy figure model in ZBrush.


Toy figure models for a collectibles producer

General / 19 September 2018

Toy figure sculptures for a producer of promotional collectibles.  


Kids room product sculptures

News / 08 September 2018

It's a pleasure to work for producers of physical products, such as a publisher of home decorations and kids room products. I created the 3D sculptures for two new products that have just been introduced: a unicorn money box and a Swan light in two sizes.

Fried — 3D artwork

General / 21 August 2018

Fried — 3D artwork (concept: Sébastien Le Divenah)