Zebra stripe curvature

Hello all,

I was wondering if OpenCASCADE has any built-in functionality that is capable of visualizing surface curvature using the "zebra stripes" method? Has anyone heard about this?

Another question: is it possible to visualize easily the isolines of a surface?

Thank you for your help
László

Timo Roth's picture

For the iso lines you can do something like this (pseudo code for OCC 6.7.1!):
AIS_InteractiveContext.DefaultDrawer().UIsoAspect().SetNumber( uCt );
AIS_InteractiveContext.DefaultDrawer().VIsoAspect().SetNumber( vCt );

Forum supervisor's picture

Dear Laszlo,
1)"zebra stripes".
I guess that rather environment map is meant (if I am wrong, correct me, please).
Using a "zebra stripes" environment map is a popular and simple method to check the curvature visually (we have some experience of using it in the past). See below Draw reproducer:

pload ALL
restore data/occ/bottom.brep b
# compute fine triangulation to obtain better "zebra stripes"
incmesh b 0.01 1
vinit
vsetdispmode 1
vdisplay b
vfit
# applying standard "striped" environment texture
vtextureenv on 6

The obtained result is attached to the post (zebra_stripes.png).
In order to get better stripes, it is necessary to prepare the texture image file in a special way (in 2:1 format, stripes should look like arcs in fact in order to pass through sphere mapping as needed) or generate it programmatically.
Also the analogical result can be obtained using "shader's" technique, but it requires more efforts.

2). "isolines"
It seems a strange question, since isolines are automatically displayed in wireframe mode. The number of isolines can be adjusted through presentation aspects.
Best regards
FSR

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Laszlo Kudela's picture

Thank you for all the answers! I've just tried out, the wireframe works very nicely!

Concerning "zebra stripes", yes, I meant the environment map (just like the attached picture of FSR). I am going to try it out soon as well.

László

Timo Roth's picture

Dear Laszlo,

did you test the "zebra stripes" and could you share some results? I'm also interested in it.

Regards

Forum supervisor's picture

Hello Timo,

Just for your information, this is how "zebra stripes" environment mapping looks in the current OCCT version.

To get a nice-looking environment mapping result, it is recommended to generate a high-resolution environment texture using a special run-time algorithm. You can contact our support services if you need help regarding this.

Best regards,
Forum Supervisor

Attachments: 
PG's picture

Looks nice, is it possible to share the BREP file with the community :)
thanks and regards

Forum supervisor's picture

The BRep model is already available in our shape gallery through this link: http://www.opencascade.org/showroom/shapegallery/gal2/