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Old   April 7, 2004, 18:43
Default Trimming surfaces
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I've got a surface which I want to trim 3 chain curves from. When it trims there are weird gaps that appear stretching between the curves. I've never had this problem before when trimming 2 chains from a surface. Is this a bug or am I doing something wrong? I've tried many different ways of trimming the curves but each time these gaps appear.

Please help as this is driving me crazy!


I'm using CFX 5.6 on WinXP.
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Old   April 8, 2004, 04:40
Default Re: Trimming surfaces
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I have seen this before. I believe it is a bug in the underlying MSC Patran geometry handling. I understand there is no workaround and you need to split the surface to create a different combination of curves in the outer/inner trimming loops
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Old   April 8, 2004, 05:39
Default Re: Trimming surfaces
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Just been having another go at it this morning and I've manage to get around it.

I translated one of the curves down slightly, without deleting the original. Then when I create the trimmed surface I just use the new curve leaving the old one alone. This seems to get around it.

I'm testing an aerofoil at different ground proximities so was intending on moving the curve anyway.

Still have to create a curve at the original height. So perhaps if I translate the curve back up it will work. Will try later.

Many thanks for your reply.

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Old   April 9, 2004, 05:39
Default Re: Trimming surfaces
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Some times in Build it can be a graphics problem and not an actual geometry problem. There is a way of dropping the graphics tolerance, If I remember it defaults to 0.001. drop this an order or 2 of magnitudes. The problem with this is that when rotating the geometry to view the model, the graphics card may not be able to cope and it becomes very jumpy. Another way to check is to increase the number of display lines (the 2 lines running horizontally and vertically through a surface). These are very useful when checking the validity of surfaces. Perviously I've had surfaces that appeared to have been trimmed with a hole through them, only to finde the display lines continuing across the supposed hole. Good Luck Bob
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