127 lines
4.7 KiB
ReStructuredText
127 lines
4.7 KiB
ReStructuredText
.. index:: Modeling Modifiers; Skin Modifier
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.. _bpy.types.SkinModifier:
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*************
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Skin Modifier
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*************
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The *Skin* modifier uses vertices and edges to create a skinned surface,
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using a per-vertex radius to better define the shape.
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The output is mostly quads, although some triangles will appear around intersections.
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It is a quick way to generate base meshes for sculpting and/or smooth organic shapes with
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arbitrary topology.
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.. note::
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Faces in the original geometry are ignored.
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Options
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=======
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.. figure:: /images/modeling_modifiers_generate_skin_panel.png
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:align: right
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:width: 300px
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The Skin modifier.
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Branch Smoothing
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A branch point is a vertex with three or more connected edges.
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These areas tend to produce more complicated topology, some of which may overlap.
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This setting relaxes the surface around these points,
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with the side effect of shrinking it.
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Symmetry
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These checkboxes are used to keep the output topology symmetrical in their respective axes.
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In other words, using it avoids merging triangles across an axis unless the triangles form a symmetric quad.
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.. note::
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They do not add geometry flipped across an axis.
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For that, the :doc:`Mirror </modeling/modifiers/generate/mirror>` modifier should be used,
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typically placed above the Skin one.
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Smooth Shading
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Output faces with smooth shading rather than flat shading.
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The smooth/flat shading of the input geometry is not preserved.
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Create Armature
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Create an armature on top of the object. Each edge becomes a bone.
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.. note::
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If the root vertex has more than one adjacent edge,
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an extra bone will be created to serve as the root.
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This tool does the following:
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#. A new armature object is added with bones matching the input mesh.
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The active selection is switched to the new armature.
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#. Weight groups are added to the input mesh. The Skin modifier propagates these weights to the output as well.
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#. An :doc:`Armature </modeling/modifiers/deform/armature>` modifier is added directly below the Skin one.
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Note that the Armature modifier is being applied after
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the Skin one because it should only deform the output,
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whereas if it were above, it might change the resulting topology.
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Add Skin Data
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This modifier uses a :ref:`custom set of data <modeling-modifiers-generate-skin-data>` in the mesh,
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that is generated automatically when you add the modifier the first time.
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However, you may remove that data, or loose it some way or the other. That operator will generate it again.
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Mark/Clear Loose
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By default, a branch vertex (vertex with three or more connected edges)
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will generate extra edge loops along adjacent edges in order to keep the output tight.
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Branches can be made loose by clicking *Mark Loose*, which will allow the output to stretch between
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all adjacent vertices. This can be disabled again by clicking *Clear Loose*.
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Mark Root
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Marking a vertex as root causes that vertex to be used for calculating rotations for connected limbs.
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Root vertices also affect the armature output, they will be used as the origin for the root bones.
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.. todo
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Not true anymore:
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Roots are shown in the *3D Viewport* with a red dashed circle around the vertex.
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Each set of connected vertices should have one root node
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(one is selected by default if you do not assign any manually).
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*Mark Root* enforces the one-root per set rule, so it is not necessary to manually unmark roots.
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Equalize Radii
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Makes the skin radii of selected vertices equal on each axis.
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.. _modeling-modifiers-generate-skin-data:
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Skin Mesh Data
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==============
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That modifier needs a set of specific data in the original mesh to work properly.
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This data allows you to define the root vertices of each tree, which ones are loose,
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and the size (radius) of the skin at each vertex. The radii of input vertices can be individually
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scaled in Edit Mode with the :doc:`/modeling/meshes/editing/mesh/transform/skin_resize`.
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Examples
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========
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.. _fig-modifier-skin-creature:
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.. figure:: /images/modeling_modifiers_generate_skin_example.png
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Simple creature, made with only the Skin and Subdivision Surface modifiers.
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External Links
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==============
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- `Skin Modifier Development at Blender Nation
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<https://www.blendernation.com/2011/03/11/skin-modifier-development/>`__ --
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An early demonstration of the Skin Modifier by Nicholas Bishop (March 2011).
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- Ji, Zhongping; Liu, Ligang; Wang, Yigang (2010).
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B-Mesh: A Fast Modeling System for Base Meshes of 3D Articulated Shapes,
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Computer Graphics Forum 29(7), pp. 2169-2178. -- The work this modifier is based on
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(`DOI 10.1111/j.1467-8659.2010.01805.x <https://doi.org/10.1111/j.1467-8659.2010.01805.x>`__).
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- `Related thread on Blender artists <https://blenderartists.org/t/499364>`__.
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