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Nurbs U & V changes

Cloud Hidden

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If I use the OIP to change the Z value of individual vertices on a nurbs surface (it's a hemisphere I'm trying to flatten), the change is visible with each point I edit, and as I get through all the U's and V's, the object is flattened to the Z I want.

If I script the same thing...a loop through the U's and an inner loop through the V's with NurbsSetPt3D...all the vertices change, but the object is still drawn to the original elevation. I use DrawNurbsObject and Reset BBox and Set3DInfo, but with no obvious effect. Only after I click the "show vertices" box and the "reverse normal" box/button in the OIP a coupla times does the surface redraw properly. Strange. So what function is being called by the Reverse Normal button that I'm missing with NurbsSetPt3D?

Edit: One solution I just discovered is to use ConvertToNurbs to convert the modified surface to another, and that one is accurate. But I'm still curious what's happening and not happening.

[ 09-15-2003, 02:48 AM: Message edited by: Cloud Hidden ]

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  • Vectorworks, Inc Employee


Originally posted by Cloud Hidden:

So what function is being called by the Reverse Normal button that I'm missing with NurbsSetPt3D?

Try calling the function RedrawAll. The reason for not triggering a redraw and bounds recomputation with every call to NurbsSetPt3D is that it can really slow things down for a complex surface with a few hundred points changing. If you're changing individual points through the object info palette, however, it's a lot slower than a VectorScript loop, so the full bounds recomputation and redrawing can be done.

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Thank you. That's the one.

VS is making it a whooooooooooooole lot quicker for me to build some of the more complex dome shapes. Latest is an oblate spheroid on a stem wall with an inner shell. Several dozen steps along with some tricky mousing to reshape the nurbs, now reduced to a menu selection and a few dimensions in a dialog. Tr? cool! Thanks for your work on VS.

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  • 4 weeks later...

Upon using the script further, it seems that RedrawAll does not cause the boundary recalc. What seems to make it redraw to match the 3D points is a solids operation, such as AddSolids (which I was adding coincidentally when I added the RedrawAll). Without the AddSolids, RedrawAll has no effect on the nurbs that I can see.

I simplified the script to show the problem. Run this with any diameter, and with a height less than D/2 and look at a side view. It draws as a hemi, but the vertices show the proper height.

Any ideas?


Procedure Oblate;


pX, pY, pZ, cx, cy, cz : REAL;

hNurbs : HANDLE;

i, j :INTEGER;



cz := DistDialog('Dome Diameter:','0') / 2.0;

hnurbs := CreateHemisphere(cx, cy, 0.0, cx, cy, cz);

cz := cz / 1.4;

cz := DistDialog('New dome height:',Num2StrF(cz));

hnurbs := ConverttoNurbs(hNurbs, false);


hNurbs:=FSActLayer; {select the base of the dome}


hNurbs:=FSActLayer; {select the dome}

i := 0;

while i < NurbsGetNumPts(hNurbs, 1) do begin

j := 0;

while j < NurbsGetNumPts(hNurbs, 0) do begin

NurbsGetPt3D (hNurbs, i, j, pX, pY, pZ);

if pz<> 0.0 then NurbsSetPt3D (hNurbs, i, j, pX, pY, cz);

j := j + 1;


i := i + 1;




Run (Oblate);

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Strange, when playing with the nurb surface on GL, I found that the closer I get to a top view the biger the hole I get on the middle of the shape??? draw a few more and he looks that if Height > Diameter the GL rendering have a problem. I don't have RW to try, but I wonder in witch cases the GL will let me down.

On a Dual 1.25 G4 OXS and plenty of ram.

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