The Documents of Stage Hands

Dynamically Additive Geometry for Sculpting in Blender

The Skin Modifier

SHThe new skin modifier can work in conjunction with Dyntopo as it enables you to quickly box-model and apply a pose rig to the model (that uses FK) and subsequently within a few minutes you’re ready to start sculpting! It’s ability to convert a set of edges and vertices to an armature is time-savingly productive and intuitive. Vertices can also be “scaled” to move the skin cluster surrounding that vertex closer towards the vertex or further away from it. Although this might sound trivial in it’s application it is in fact the basis on which creating the initial form of a model for dynamic sculpting is determined. A general technique for working with the skin modifier to create a base model for dynamic sculpting is to,

1 First create a stick figure with vertices and edges. This will then form the armature used for the model’s pose rig.

2Once the skin is created go through each vertex and set it’s scale for the skin, Blender conveniently provides realtime feedback, by re-calculating the skin’s geometry with every tweak made.

It’s important to note that the geometry that the skin modifier creates in areas where vertices are close together might not always turn out as expected. These areas can result in non-manifold geometry, leaving tears in your mesh.
If this cannot be fixed by scaling or translating the relevant vertices, you might need to rebuild that particular part of the mesh in edit mode then re-assign weights to the pose rig.

Although one of the major advantages of dynamically sculpting is that base models do not need to rely on perfectly placed edge loops for subdivision, it’s still worth starting a dynamic sculpt with a mesh that represents a clean shell of your model that does not have non-manifold geometry intersecting the mesh’s interior volume.

! Geometry that is obscured in such a manner by the mesh’s exterior (or shell) will also be tessellated during dynamic sculpting, but will serve no useful purpose and contribute to increasing your model’s polycount sometimes with drastic effects.

In some instances when the desired result for sculpting a certain area is just not manifesting as you’d hoped in your model, it might be best to drop into edit mode and delete the polygons comprising that area then close the resulting hole with a few ngons, before making a second attempt. This can substantially keep polycounts at a manageable level and in conjunction with hiding geometry provides near realtime feedback on extremely dense meshes that have been reworked several times.

Retopologizing a Dyntopo Model

SHNot all models created with dynamic sculpting need to be retopologized. A few of the reasons you might consider retopologizing your model include,
  • if you want to create a workable UV layout that can be used for texture painting etc,
  • if your model is intended for continuously deforming animation (such as in character animation),
  • if you want to export your model to another 3D application or games engine and working with a high poly count could really slow the system down.

A particularly useful feature when retopologizing is the snap to faces button. Once this button is enabled, it’s just a simple case of extruding vertices to create the desired edge loops. Then selecting edges and creating polygons. It’s always very tempting to create a fully quadrangulated mesh through retopologizing however this is not always necessary and in certain instances when the mesh is intended for a static shot using ngons in the model could speed up the modelling process and have no visible effect on the quality of the rendering.

Once a retopologized mesh is created, it’s a simple case of creating a normal map if desired and/or using multires and shrinkwrap modifiers to retain the sculpted details and maintain a manageable, deformable model.