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This task shows you how to perform a symmetry on a subdivision surface. |
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There are two types of symmetry:
- no intersection between the subdivision surface and the symmetry
plane
- intersection between the subdivision surface and the symmetry plane.
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Open the Symmetry1.CATPart
document (without intersection) or Symmetry2.CATPart
document (with intersection). |
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Click Symmetry .
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Select a surface.
The
Plane Selection icon
becomes active. |
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Select the plane.
You can also select the plane first then the surface. In this
case, the Surface Selection
becomes active. |
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No intersection between the subdivision surface and the symmetry plane
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The result is the mathematical symmetry by a plane: |
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Intersection between the surface and the plane
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In this case, the surface is made of two parts separated by the plane. A
side of the surface is automatically chosen, corresponding to the
bigger side: |
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A new icon
appears in the Tools Palette to let you choose the side. |
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Select Side Selection
or
click in the 3D area to invert the side of the symmetry.
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- The symmetry keeps the curvature continuity of the subdivision surface,
therefore some details of the input mesh will be modified.
- Previous operations
performed on the input surface are also kept.
- The result of the symmetry is a subdivision surface. Thus, you can
perform a symmetry of a symmetry or copy-paste a symmetry or use this
feature to associate other subdivision surfaces.
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- If the surface is U-shaped, you cannot select a
side as it is automatically chosen:
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- If the symmetry plane intersects a S-shaped surface, the symmetry cannot be
performed.
Below is an example using the green plane: the symmetry cannot
be performed. |
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Below is an example using the red plane: the symmetry can be
performed. |
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- If the face of the surface has only one vertex on the chosen side,
the result of the symmetry is a mirror surface.
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Copy and Paste a Symmetry
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When copying and pasting a subdivision surface that is a symmetry, a dialog
box opens: |
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Create a sharp edge
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To create a sharp edge at the symmetry plane, the subdivision surface must
intersect the plane and a sharp edge must already exist. |
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