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 Spin Poly 2.0
Description
'spinPoly' is a modeling plugin
for Cinema 4D 6,7,8 or 9. It provides a quick and easy way to modify
the meshing of a polygon object by 'spinning' the shared edge(s) in a selection. It consists of a single button, whose operation
is context sensitive based on the current selection.
Simply make a valid polygon selection (described below), then apply the plugin
one or more times to convert the meshing of the selection to the desired
form. The plugin through each of the meshing options in turn. This is a much faster process than deleting
the orginal polygons then creating new polygons.
Any UVW texturing already applied to the object will be preserved by spinPoly
as it automatically updates the UVW coordinates of the modified polygons
to suit the new meshing. Multiple UVW tags are supported and will all be
updated. This means that you can still modify the mesh layout even after
texturing. Because spinPoly only modifies polygons, not vertices, then any weight maps you have will also be left undisturbed.
The following images provide examples of valid selections, and show what
spinPoly will do in each case. Note that in all cases repeated application
eventually returns to the original structure. Click for larger images.
Valid selections are:
- Any single quad (four sided polygon).
- Any two adjacent polygons (sharing a single edge).
- All polygons connected to a single vertex (where all polygons share a single edge with their neighbour).
If the selection consists
of two adjacent triangles then in addition to spinning the edge (equivalent
to swapping the diagonal), the plugin also provides the option of merging
the two triangles into a single quad, and also the splitting of a single
quad into two triangles - which is why a selection of a single quad is also
permitted (splitting and unsplitting of a quad can also be performed using
the inbuilt Cinema4D functions 'triangulate' and 'untriangulate', but from
a workflow point of view it is faster to do it using spinPoly).
Uses
This tool is useful for:-
Mesh Flow adjustment
Adjusting the 'flow' of polygons
over the surface of an object, which is useful for keeping the mesh structured.
This is important to support ongoing modelling operations, and to give more
predictable HyperNURBs smoothing.
The image sequence below shows some simple examples of using spinPoly to
change the flow of the mesh. In each image, the green groups are the selections
that are used with spinPoly in order to produce the mesh shown in the next
image. Note that each group must be selected seperately. I.e. the first image
show three seperate selections that are used in turn with spinPoly.
Triangle elimination
It is sometimes desirable to avoid triangles in a mesh - e.g. with HyperNURBS..
By selecting a triangle and an adjacent quad, the plugin can be used to 'spin'
the triangle to one of the other sides of the quad. This can then be repeated
with a different quad selected, in order to move a triangle around the mesh.
Once two triangles are adjacent, they can be selected and then merged into
a quad, once again by using the plugin. An example is shown below. In the
first image there are four seperate triangles in the mesh. By the final image
they have all been converted to quads.
Degenerate triangle repair
Sometimes (especially after boolean operations) you may find that you have
some long but very thin triangles in your structure. These are generally
undesirable because they are difficult to work with and can cause shading
artefacts in extreme cases. By using the plugin on these triangles, their
quality can often be improved.
Bad Normals
Repairing
'bad normals' on quads. Sometimes, especially with quads which have two adjacent
edges close to parallel, C4D will calculate a poor quality normal which can
produce shading artefacts. Whenever spinPoly generates a quad, it ensures
that its internal representation is such that C4D will generate a good quality
normal wherever possible. If you have a quad which may have a bad normal
(i.e. it is giving shading artefacts) then select it, and apply spinPoly
three times. This will cycle through the two alternate triangulations, and
then back to a quad. The resulting quad will have a normal which should be
better than the original. In particular, if you have any quads which C4D
is reporting as degenerte, try running spinPoly on them as it can fix some
of these cases. The mesh will not look visibly any different, but spinPoly
ensures that the internal representation gives a good normal.
Anything else!
And of course, any other time when you want to be able to change the meshing of an object for your own purposes.
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