C4D插件：spinPoly 2.0（商业）

Description

'spinPoly' is a modeling plugin for Cinema 4D, providing a quick, easy way to modify the layout of a polygon mesh object by 'spinning' 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 cycles through each of the meshing options in turn - which is a much faster process than deleting the original polygons then creating new polygons.

Any UVW texturing already applied to the object is 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.

These images show examples of valid selections, and what spinPoly will do in each case. 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 (swapping the diagonal), you can also merge them into a single quad. A single Quad can similarly be split into two triangles (As with the Cinema4D functions 'triangulate' and 'untriangulate' - but it is faster workflow 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. Here are some simple examples of using spinPoly to change the flow of the mesh. 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.

uses1

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.
uses2

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.
uses3

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.