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View Full Version : Why are 5 edged verticies bad?


tredeger
08-22-2003, 11:40 PM
I've been reading a lot of the edge looping threads and they discuss numerous techniques for maintaining an all quad surface. It's quite common to join divergent rows of quads with quads whose orientation relative to the rows makes it a diamond or dart of sorts in the surface.

In some cases, this results in three quad faces terminating in a single vertex. As I understand it, there is absolutely nothing wrong with this. In other cases, five faces come together at a single vertex and I've seen several threads that say this is a bad thing (but OK if there is a natural wrinkle there). But I haven't found an explanation as to why this is bad. What happens? And is there a general pattern or solution to correct this?

Thanks in advance to all you polymodeling geniuses out there.

Stroker
08-23-2003, 01:38 AM
The only problem I've ever had is an annoying shading error, which will probably become more pronounced with MeshSmooth (or equivalent).

jud
08-24-2003, 10:36 AM
I know that when I am modelling that I always try to stick to quads and avoid triangles or faces with 5 vertices as it tends to cause the mesh to "pinch" when it is subdivided,but there are apps out there that can handle tri's and so on,but most apps use catmul clark subdivision and quads are prefered so as to keep good symmetry for the model.
When a model is subdivided each of it's faces are divided into smaller faces but in that area if you have a face that is split in 2 by an edge going from one corner and across to the opposite corner then that area is going to conatin more detail when it is subdivided,now! that won't cause you too many problems in some apps but if the edge was going through the face from one edge to the opposite edge leaving you with faces on the outside with 5 vertices then you are going to have problems with pinching and so on,the catmul clark subdivision use's quads when subdividing the mesh so when modelling you should model using quads.
For an example, if you create a cube and add a vertice on one of its edges and then quad-divide the face you will see that it does not quad divide it properly due to the vertice on the edge.

I think that sounds about right but im sure if I am wrong that someone here will point it out.

Cheers
:beer:

jud

actarusprocyon
08-25-2003, 02:41 PM
I think tredeger means to talk about Five edged Vertice * Star pattern occuring where edgeloops meet which I have a hard time getting rid of as well but have found no rendering/shading problem related to it.

I've seen many excellent models having those.

jud
08-27-2003, 02:16 PM
I suppose it comes down to the app you are running as some apps don't handle "odd" geometry and some handle it very well,I have also seen highly detailed models using tri's and 5 edged shapes.

jud

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