Help with Velodrome and Nurbs.

[LukeNevegsa]

Hi there New comer here,

I have been struggling to create a velodrome type curve for a while now and managed it using a combination of NURBS and project and add. But for some reason it won't work again after i did it for the first time.

When i try to project and add it asks me to select the 'Closed Planar Profile' (im presuming thats the poly that the Nurb will project onto) but it won't let me select the 2D poly i created...it is probably something to do with the fact that i did something without realizing it and simply can't remember but i would really appreciate some help! My terminology will probably be below par in afraid but i will try to answer any questions you have with what limited knowledge i have.

I will talk you through what i did:

First i created a 3d semi circle

Converted it to Nurbs

De grouped it and changed the value on the 'top' to create the curve

Deleted the side/front of the semi circle to leave the top and bottom of the 3d object (see image)

Projected the top Nurbs curve down to the bottom to create a solid object.

At this point it won't let me select the bottom Nurbs object so i make a 2D poly in the same shape and it still wont work.

Tearing my hair out over this one because i did it once before!

Thanks in advance for any help you could give me

[Benson Shaw]

I can't quite follow your method, but I think you cannot select for projection because your earlier steps made a NURBS surface. The Project Tool works with NURBS curves. You could extract a curve, then project.

Another way forward:

In top view

Start with a 2d arc, close the open side with a 2d line, Compose.

Modify>Convert to NURBS

Model>3dPowerPack>Create Surface from Curves.

In OIP set V Degree to 2

Switch to side view

Duplicate

With only the new NURBS surface selected,

Set OIP Move box to V Verticies.

Raise the OIP z value of the crest v vertices. Z = prox radius of curve.

If nec, adjust z height of middle set of v's.

Now you have a semi circular NURBS surface on the ground plane, and the velo NURBS surface rising out of the plane.

Loft to make the sides:

Activate the Extract Tool and extract the curve from both surfaces. Hold the shift key to make the multiple extraction.

Enter the group & create a simple loft between the two curves. Choose Ruled option for straight sides.

Good luck

-B

[willofmaine]

Or maybe consider using a Loft Surface. You could draw (in front or side view) sloped lines at various angles representing the changing pitch around the track. Then convert them to NURBS curves (a straight line can be a NURBS 'curve'). Then, in plan view locate them radially along your track, say every 15 degrees. Then use the Loft Surface command with 'no Rail mode' to create a NURBS surface that connects the lines...

[LukeNevegsa]

Thanks very much for your help!

Think i may of cracked it now.

Luke