Props: Skinning or Vertex Manipulation?

Sep 20, 2022 at 07:30 am by Warlord720

Using bones with skinning is nothing new to long-time Renderosity readers. Vertex animation or morphing as it is more commonly known is just as familiar as well. Morphing has become a “go-to” method for a lot of Renderosity 3D’ers leaving the skin and bones method to a more meager existence amongst newer users.

Why learn about bones and skinning when you can just reshape things? I can understand the reluctance of many that prefer morphing over skinning, but modern skinning tools have greatly reduced the difficult part of using bones. In the case of a simple prop like a table... the addition of bones with simple skinning (usually the click of a few buttons – we aren’t talking about skinning fingers) of a handful of simple bone chains (point and click) will make it a walking table or many other things depending on the number of bones you use and where you place them.

To be clear, bones drive morphs too as they are not all just a reshaping of the mesh. A mesh-driven morph takes a bit more time and preparation as one needs to be mindful of what parts are going to move during development. Using bones mainly requires a clean topology for the bones to bend their specific area properly without too much stretch, binding, or caving.

Before it was known as morphing, we called it vertex animation. In 3DS Max all you had to do was turn on Auto Key, slide down the timeline and move or manipulate a part of the prop mesh, like a door that opened and closed. This was usually done with individual objects. Most 3D applications offer this method.

When skinning was more finicky, before all the tools and tweaks became available, it could be a tedious process that most newbies associate with characters not realizing that props were the same. Envelopes have to be a lot more precise for characters in most cases. Props can be much more forgiving than a character.

Let’s take a look at this in the most fundamental form that can be accomplished via vertex animation whereas adding a bone and skinning would be two unnecessary extra steps. Both accomplish the same thing, but vertex or morphing makes more sense.

Prop Manipulation

In the above case, all I had to do was grab the top of the box (with the pivot set to the hinge area) then turn on Auto Key, move the slider down the timeline, and open the lid. This creates two keyframes, one at the beginning and one at the end point of the action. To some people, true vertex manipulation is the resculpting of existing mesh but it also refers to parts of a mesh that can be selected and manipulated up and down the timeline.

In the case of a more fanciful, but simple, prop let's look at animating a table for a children’s tale. We need to add at least one bone per leg or use bone chains on the legs then skin them to the table. None of this is rocket science, just basics.

Bones and Skinning

As you can see in the table props above you can use just a few bones or several bones depending on what your needs are. The more bones the smoother the movement and the easier it is to not distort the UV mapping visible in the middle left table that has the one-bone legs. The multi-bone legs can be moved from below the top bone sticking the tabletop in place without stretching the mapping.

You can also use multiple bones to reshape the table legs to a more fanciful design or animate them in a walking, running motion or as is more practical, the legs can fold up and down. Animated furniture is not that unusual in projects for kids. Already fickle, young viewers need something novel to grab their attention, and bringing a table to life could be the attention-getter you are looking for.

In the end, it matters how complicated the props are and what you intend to do with them. In some cases, simple vertex manipulation up or down the timeline will work while other props like ropes, hoses, or pipes may work better with bones skinned to the mesh.

M.D. McCallum, aka WarLord, is an international award-winning commercial graphics artist, 3D animator, published author, project director, and webmaster with a freelance career that spans over 20 years.  Now retired, M.D. is currently working part-time on writing and select character development projects. You can learn more about MD on his website

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