tlehnhaeuser Posted July 31, 2002 Share Posted July 31, 2002 I have heard other apps boasting of ZEBRA tracing. Isn't thatg the same as just dragging a line image from our abstract catalog onto surface and setting to NATURAL? Can anyone debate this? Quote Link to comment Share on other sites More sharing options...
Chris Lohman Posted July 31, 2002 Share Posted July 31, 2002 Found here, I quote "Zebra analysis, which is found in some other packages, plots zebra stripes over your model as if it were chromium-plated and placed inside a striped cylinder. G0 surfaces, which meet edge to edge, show disjointed stripes; G1 surfaces, which are tangency continuous, show stripes that may be continuous, but have kinks; and G2 surfaces, which are tangency and curvature continuous, show smoothly flowing stripes. One problem with zebra stripes is that as you change your view of the model, the stripe patterns change so it can be difficult to analyze blends from several different angles." Quote Link to comment Share on other sites More sharing options...
Guest dlalonde Posted July 31, 2002 Share Posted July 31, 2002 In Rhino, zebra stripe is a specific case of Environment Map Surface Analysis, in which stripes or some other image is reflected by the part in realtime as you rotate pan zoom etc. The effect is stunning and very revealing. Still pictures don't do justice to it but here are examples of each... Zebra stripe.... Environment mapped image... I want this built into Ironcad. Quote Link to comment Share on other sites More sharing options...
Guest Scott Wallis Posted July 31, 2002 Share Posted July 31, 2002 The fact that zebra stripes or environment maps ( in a program like Rhino) move across the surface while you rotate the part makes them more useful for finding surface irregularities. It is like holding a part up to the light and rolling it around to see how the light and reflections fall across the surface. You can detect smaller defects that way than with a static mapped grid. It has always amazed me how Rhino can do such a great job dynamically rendering a surface with an environment map when their rendering in the working scene is rather unimpressive. (compared to IC) Scott Quote Link to comment Share on other sites More sharing options...
tlehnhaeuser Posted August 1, 2002 Author Share Posted August 1, 2002 I'm a bit thick on this subject. The overall purpose of zebra surfaces is to detect continuity to INDIVIDUAL surfaces..right? The stripe must therefore have a consistant pattern on EACH surface. The below image shows that all the surfaces are correct because the stripes are constant on EACH surface. Please correct me if I'm wrong. Quote Link to comment Share on other sites More sharing options...
Guest Scott Wallis Posted August 1, 2002 Share Posted August 1, 2002 I would think the term continuity would mean surface to surface matching. To accomplish that it has to apply the stripes across all surfaces seamlessly. In this way you can detect edge mismatch and also analyze the entire part's curvature. Again, I think any static rendering will only have limited usefulness. The attached file is a rendering from an IC scene. The stripes are projected on the surface using a striped .bmp image as a gel on a spotlight. The surface finish of the part is "mirror" from the surfaces catalog. No other lights are on and ambient is 0. Be sure to crank the surface smoothness all the way up. It's fun to play with, not sure of the usefullness. Even being able to orbit the camera while fully rendered would not help as the stripes would move with the part. You would have to actually rotate the part or move the spotlight while rendered. Scott Quote Link to comment Share on other sites More sharing options...
Guest dlalonde Posted August 2, 2002 Share Posted August 2, 2002 From the Rhino help on Zebra Stripe Surface Analysis... The Zebra command is one of a series of visual surface analysis commands. These commands use NURBS surface evaluation and rendering techniques to help you visually analyze surface smoothness, curvature, and other important properties. If the stripes have kinks or jump sideways as they cross the connection from one surface to the next, the surfaces touch, but have a kink or crease at the point where the zebra stripes jag. This indicates G0 (position only) continuity between the surfaces. If the stripes line up as they cross the connection but turn sharply at the connection, this means the position and tangency between the surfaces matches. This indicates G1 (position + tangency) continuity between the surfaces. Surfaces that are connected with Fillet display this behavior. If the stripes match and continue smoothly over the connection, this means the position, tangency, and curvature between the surfaces match. This indicates G2 (position + tangency + curvature) continuity between the surfaces. Surfaces connected with BlendSrf, MatchSrf, or NetworkSrf display this behavior. The NetworkSrf options allow any of these connections when you use surface edges as part of the curve network. Quote Link to comment Share on other sites More sharing options...
Chris Lohman Posted August 2, 2002 Share Posted August 2, 2002 So this ZEBRA tracing appears to be very useful for surfacing but I don't see much use for it with solid's. I suppose it might help with lofting and sweeping, maybe. When we create surfaces they're very defined and restricted. A nurbs modeler creates surfaces by simply mapping points so I can understand how there's a very high chance to map a triangle wrong and end up with a skewed surface. I feel that there is a very slim chance that this could be useful in the current ironcad in very very limited situations, but it doesn't seem like it would be *that* usefule. We are moving towards the ability to create more freeform surfaces in IronCAD in the future so perhaps the need will grow once we have that functionality. Can anyone think of an example in IronCAD where, when rendered in smooth shading you might not see a surface deviation, but with Zebra you would see it? I can't think of anyways to even create a surface like that. If you create a loft and it's match points are off, the geometry twist and gnarls and the edge representation makes the deviation obvious. Any ideas? Scott: That's a cool rendering. Quote Link to comment Share on other sites More sharing options...
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