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Newbie - Boundary Surface Question


New member
View attachment 125

Hey all - I'm working on a school project which involves modeling a snowmobile. I am having problems modeling the complex shape of the hood. I've read MANY threads on here dealing with surfaces and I have learned quite a lot about curves and surfaces, thanks. I created the curves by - adding points, adding a single curve between the two end points, and tweaking the curve to the correct shape. If there is a better way to make the curves, just let me know.

So the problem now is, I can't seem to figure out how to create surfaces between some of the curves. I need to create a surface bounded by the curves selected in the pic. I've tried boundary curves and style but it seems that you can only select 3 or 4 curves? Also, you can see that some of the curves extend outside the area I want to surface. Do I need to shorten those so they end at the corners of the boundary? If so, how do I do that? The only solution I can come up with is to create curves to divide the area up into 4-sided regions. I would think this approach would make the surface look patchy. Thanks a bunch, I really appreciate the help and patience!!


New member
Since no one has chimed in, I'll offer some help.

First, to answer your questions in order:

Is there a better way to make curves?

Well, there are several ways to make curves, all have advantages. In this early stage of the model I wouldn't start with tweaked curves, since they are harder to modify parametrically. You may want to start with the basic plan and elevation views of the hood as sketched curves. That way you can easily control dimensions and shape later. Curves through points are very useful for some featues, but I would start with them in this case. can only select 3 or 4 curves?

True, with boundries or ISDX you need 3 or 4 curves (4 is preferable) If all of your curves lie in one plane, simply use the fill tool to create a flat surface. If they do not, your best bet is to rethink the surfaces and create curves to define them using 4 boundries. You can use the n-sided patch feature found under Insert>Advanced to create a surface with more than 4 boundries.

Do I need to shorten curves?

In Wildfire, usually not. You still can if they give you trouble. It's done from within Boundry Surface tool. Select the curve, then right mouse button on the endpoint and choose trim at. Then click the reference point to trim to (usually a datum point or the intersecting boundry curve.)

As for making a surface look patchy that's where your edge alignment comes into play. If you want one surface to flow into the next, first the coresponding curves must be tagent or curvature continuous with each other, then you must set the edge alignment (in the boundry tool) so that the surface is tangent or curvature continuous with its adjacent surface.

Good curves make good surfaces! Conversly, crap curves make crap surfaces.

Good luck.


New member
I cannot speak for Wildfire, but think I can help you. Choose the uppermost curve for your first set of curves in the first direction. Choose Done until it asks for the second curve. Choose the bottom curve and trim it back to the intersection. Choose done until it asks you for curve 3. Change the mode to second direction. You might have to go into Chain mode (in chain mode, you can select more than one curve) to select different curves (You have to in 2001). Select the curves on the right, choose Done until it asks you for the second set of curves. On the last set of curves, you might have to create a copy of the straight curve which is trimmed back to the intersection (in 2001 you can only trim the ends of curves). Choose your leftmost set of curves (chain). You should have been able to choose 2 sets of curves in the first direction and two in the second direction. You can now apply tangent or normal conditions to your patch.