Size and topplan view of imported geometry incorrect, opengl good

[Bas Vellekoop]

Hi,

Some strange thing:

I imported a 3d-file from 3M, a simple bumpon

(igs stp x--t, doenst mather what kind of file type).

The size of the object is not correct in the OIP, it should be around 2mm thick.

Another problem is that the wireframe is different then the opengl render mode. Opengl shows to correct object, wireframe shows it smaller.

If I extract nurbs surfaces from the object I get the right sized object and views in wireframe and opengl.

Whats happening here?

(wasn't able to upload the igs/stp/x--t files so hereby a link:

http://solutions.3m.com/wps/portal/3M/en_US/Electronics_NA/Electronics/Products/Electronics_Product_Catalog/~/3M-Bumpon-Protective-Product-SJ5302-Clear-0-312-in-wide-x-085-in-high-15-000-pcs-case?N=8704948+3294003126&rt=rud)

Edited March 10, 2016 by Bas Vellekoop

[Kevin McAllister]

I'd say the size of the object isn't correct in the manufacturer's file. I tested an import into Rhino and VW. The object size is the same in both cases. Also, if you look at their filename it contains xx which I think means the manufacturer has uploaded a generic size that represents various model numbers.

Can you just scale the object to the correct size using the data from the manufacturer's website?

The object seems to be the same size in both render modes for me. Is it because you can't see the top of the curve in wireframe that you think its different? VW will often not show the extents of 3d curved faces in wireframe.

Kevin

Edited March 10, 2016 by Kevin McAllister

[PVA - Admin]

Wireframe sometimes tries to oversimplify its expression of curved surfaces. I'll download and take a look and submit, ideally it shouldn't be shaving off such a significant portion of the top curve of a solid.

[Bas Vellekoop]

Can you just scale the object to the correct size using the data from the manufacturer's website?

If u extract nurbs surfaces in open-gl and then add them together then the new object is the right size.

That makes me think there is something going wrong with the import. In Rhino its 2mm thick?

[Kevin McAllister]

Here's what the object measures for me. Its within the tolerances in their PDF file which contains dimensions.

Kevin

Edited March 11, 2016 by Kevin McAllister

[Art V]

Wireframe sometimes tries to oversimplify its expression of curved surfaces. I'll download and take a look and submit, ideally it shouldn't be shaving off such a significant portion of the top curve of a solid.

Jim, while you are taking this up with software engineering, could you please also have them take a look at how the edges of curved surfaces are shown in 3D wireframe views.

E.g. when trying to align with the edge of an extruded circle it often happens that the edge of the extrusion is "beyond" the edge of the surface lines shown. It would be nice if in any view it would show the outmost boundary line (i.e. line up with the edge of the circle in this case).

This becomes an issue when two surfaces are against each other and one appears to be extending outside the edge of the other object whereas that is actually not the case case. I always have to check if things are correct or not, so it would be a timesaver if the display in wireframe could be improved.

[PVA - Admin]

To clarify, do you mean the issue detailed below, where surfaces are not fully represented in wireframe depending on the angle viewed from?

Two parametric solids, one circular extrude and one sphere in OpenGL, the edges are clearly defined:

In wireframe from the same view, you can see the side edges of the cylinder on the sides do not match the actual side surfaces of the object. For the sphere, there is a clear line defining the surface which persists from all angles:

However if I modify the sphere so that it is a solid subtraction, we no longer get that defining line to show the surface, it appears that the object is warped in wireframe when in fact the left face is still smooth in opengl:

[Art V]

Yes, that is exactly what I meant.

When working in wireframe I keep running into the issue whether some objects of different shape do line up at their actual edges or not, e.g. with a cone and a cylinder where the cone base seems to have a larger radius than the cylinder because their outermost edges show differently in wireframe but it is ok in OpenGL mode.