Geometry problem ?

Hi,

I’m trying to load the BikeFromXSI.dae file from :

http://collada.org/owl/browse.php?sess=0&parent=123&expand=1&order=name&curview=0&sortname=ASC

But I got a problem with the geometry when I try to calculate the normal,
because I have 2 identical points coordinates for the same polygon :

The geometry name is : “geometries_7”

Polygon index : 1737 (index start at 0)

in

…</p> at the 6948 (1737*4) index, I got the following vertices indexes :
vertex indice = 828
vertex indice = 107
vertex indice = 802
vertex indice = 2070

And then the following vertices …

Here are the positions of the vertices :
(-0,669677972793579, 0,797966003417969, 0,669677972793579)
(-0,669677972793579, 0,797966003417969, 0,669677972793579)
(-0,786494970321655, 0,797966003417969, 0,525873005390167)
(-0,786494970321655, 0,797966003417969, 0,525873005390167)

How it is possible to have several times the same coordinates for this polygon ?

Yes it’s possible for a polygon to have coincident vertices. It’s called a “degenerate polygon” and is almost always considered bad modeling (unless there is a non-visual reason for it to exist). In this case it appears to be a quad that is actually a line.

Thanks for your answer,

So, I can bypass all the polygons that have some Normals with lenght = 0.

But the, I still have a problem when loading my Collada model, here is the result I got :
http://picasaweb.google.com/viewon01/OpenGL#5391730633418058914

Do you see that some face are not correctly drawed ? I search to fix this problem since several weeks without a solution, can you help me please ?

Continue what you’re doing: isolate and debug the problem polygons to determine what the problem is in each case.

Try using your favorite modeling tool to process and clean up the data and re-export it.