[GiDlist] Rendering problem

[Mark Smith]

GiD6.3.0b Win98

Hi GiDteam
The attached geometry file is of a cone with a spherical cap surface, it
displays OK in normal mode & meshes correctly but when the geometry is
rendered only the conical part shows ? Why?

Are there any rules to sweeping out a line or curve into a valid surfaces, I
generated the geometry by copy-rotate-extrude a line and an arc but
depending on the angle swept through the surface might appear OK when meshed
it reported surface errors ?

Regards
Mark





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[Enrique Escolano]

The render algorithm is faster than the mesh generatio, but less robust.
Some surfaces can be correct although
it fails the render.

The surfaces of GiD are parametric (except planar surfaces), the parameter
space is a mormalized square of side 1x1.
The parameterization send a point on this space parameter to the 3D real
space.

Typical problem (to render, mesh, intersections, etc):
The inverse of the parmeterization not exist, two or more points on 2D are
mapped at the same point in 3D.

For example:
- A point located over the rotation axis generate a singular point
- A rotation of 360 degrees creating a "closed" surface (cilinder, cone,
torus, sphere)
- Cone Vertex

Try to avoid this cases if possible.

Others problems:
If you need to mesh the volume of the cone, and the surface is divided only
in two pieces, then in the vertex are generated two triangle faces with the
same three nodes, and it is not possible to create a tetrahedra inside.
Divide the cone in three or more surfaces.

Enrique

----- Original Message -----
From: "Mark Smith" mark.smith at linx.co.uk
To: gidlist at gatxan.cimne.upc.es
Sent: Wednesday, August 28, 2002 5:20 PM
Subject: [GiDlist] Rendering problem


GiD6.3.0b Win98

Hi GiDteam
The attached geometry file is of a cone with a spherical cap surface, it
displays OK in normal mode & meshes correctly but when the geometry is
rendered only the conical part shows ? Why?

Are there any rules to sweeping out a line or curve into a valid surfaces,
I
generated the geometry by copy-rotate-extrude a line and an arc but
depending on the angle swept through the surface might appear OK when
meshed
it reported surface errors ?

Regards
Mark





--------------------------------------------------------------------------
Linx Printing Technologies plc
+44 (0)1480302100
http://www.linx.co.uk/
This e-mail may contain privileged/confidential information and may be
read, copied and used only by the intended recipient. If you have received
it in error, please contact the sender by return e-mail or by
telephoning +44 (0)1480 302100.
Please then delete the e-mail and do not disclose its contents to any
person.

Any information in this message that does not relate to the official
business of Linx shall be understood as neither given nor endorsed by
Linx.
We reserve the right to monitor all e-mail communications through our
internal and external networks.
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