Webspace question - Mirroring worked...but not anymore :-(

Marvin Landis ([email protected])
Tue, 17 Oct 1995 17:13:32 -0700


OK, this was brought to my attention by a couple of SGI employees that had been
using WebSpace 1.1 before the rest of us, but I wanted to wait until I could
try it myself before I asked some questions about it. I've now downloaded 1.1
and experimented some, so here come the questions.

They noticed that the left side of my dulcimer object was not displaying
correctly (http://amber.rc.arizona.edu/vrml/dulcimer.wrl.gz), probably a
backface culling problem. The technique I used worked fine with WebSpace 1.0,
but is definitely not working with 1.1. I used a common modeling technique to
mirror the right side of the dulcimer to get the left side, namely scaling -1
along the z-axis. Here is a simple excerpt from the model:

DEF TOP Separator {
Coordinate3 {
point [...coords deleted...]
}
DEF TOP0 IndexedFaceSet {
coordIndex [...indices deleted...]
}
Transform {
translation 0 0 1.2
scaleFactor 1 1 -1
}
ShapeHints {
vertexOrdering CLOCKWISE
}
USE TOP0
}

So TOP0, is the eight, top side of the dulcimer, and it displays fine. I then
use the mirroring transformation, and use the TOP0 definition to display the
top, left side (I did have to change the vertexOrdering hint to CLOCKWISE for
the top, left side to display with Webspace 1.0, which I thought was strange,
but it worked).

I was hoping that when I got my hands on WebSpace 1.1, that changing the
CLOCKWISE back to COUNTERCLOCKWISE would cause the dulcimer to display
correctly, but it doesn't make a difserence. Changing the shapeType hint also
makes no difserence at all.

So is it not possible to use this mirroring technique? Do I have to mirror the
top in my modeler and actually include the coordinates and face indexes in the
VRML file? It's a shame if I do, because the top is the most detailed part of
the object, thanks to the hummingbird and flower cutouts, and it would increase
the file size significantly.

Anyone got any suggestions?

-- 
Marvin Landis
WWW Page:	http://amber.rc.arizona.edu/marvinl.html
Email:		[email protected]

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