help asap with extrude along path

[stevewright]

I have to create a cylindrical duct, to form over the shape of a building. I used the extrude along path tool, which gave me the perfect shape in elevation, however in plan it is completely linear- I need to also have it weaving left and right in plan and elevation. Is there a way to create a double extrude path, or create it in elevation, then manipulate the shape in plan?

[Delmer]

You will need to do the manipulation you speak of on the path. You may have to set a working plane or two where the path moves vertically. Use the 3D reshape tool to adjust the path.

You can also make the duct out of HVAC components. Check the Show 3D detail on the OIP. I don't believe the HVAC tool will allow you to do slopes in the Z plane however, just straight verticals.

[ 06-02-2005, 10:18 AM: Message edited by: Delmer ]

[stevewright]

i tried adjusting the path, but it keeps saying its invalid when i click exit group. I also tried creating the surface with nurbs, but once again, once i edit the path using the 3d edit tool, it says the path is invalid

[Delmer]

Its very possible that one or more of your corners are too sharp for the radius of circle you are extruding.

[Kaare Baekgaard]

try add-solid two shapes, use the extract tool to get the wavy path, and use this path to do the extrude along path command.

[Delmer]

The HVAC tool has its uses. If you do need contortions that are outside of its parameters you can ungroup an item and it will become a simple extrude, sweep or whatever, and can be rotated or adjusted as such.

If you stick with the path you still might consider breaking it up into components to isolate where it is unhappy.

[stevewright]

I tried once again, with the path object not having any sharp turns, and the radius of circle being small, but still it tells me theres an invalid path or profile object. i cant add two objects, cause it wont let me create even part of the shape, and as it needs to twist in 3dimensions, it would be difficult to line it up. Whats the hvac tool?

[Delmer]

The extrude along path is too touchy. You might try copying your path and pasting it anew. Adjust it to exactly how you want it and then if it won't take as a new extrusion path trace it with a brand new nurbs curve. Before tracing double-click the Snap to Objects constraint and check the box in there. Turn off all other snaps.

The HVAC tool may only be in the industry series. It supplies you with a series of splitters dampers elbows etc.

[Delmer]

I can't say this it true 100% of the time, but it seems that if you start with a polyline and use it as a path, it will be converted to a nurb and you can edit the path only if you stay within the original plane. Same if you convert it to a nurb yourself before doing the extrude.

If you start off drawing a nurb for a path you are able to twist it almost any way you want.

[stevewright]

thanks for your help, after much messing around, i finally got the shape i required by drawing completely new using nurbs. However, ive done one duct, but i need a further 3.... I tried repeating the process, but just when i get the path perfect in one view, when i switch to the other to edit it there, the whole thing gets distorted. Im having majorly trouble trying to control the nurbs shape, even when using the different constraints

[mike m oz]

Try using 3D loci as points to snap your nurbs curve to.

- Locate the 3D loci in Top/Plan View first and then adjust their Z heights.

- Draw your nurbs curve in Top/Plan View by interpolation point.

- Go to an elevation view and choose the 3D reshape Tool and set it to the Move nurbs curve along Z axis mode

- Move each vertex so that it snaps to the 3D loci immediately above it.

- draw your shape to extrude and then Extrude Along Path

if this is a real project at the end of the day someone has to build these ducts. Unfortunately sheet metal has its limitations and it may in fact be very difficult to construct what you have drawn. You may be better off rationalising them to something which can be modelled with the HVAC elements.

A limitation of the HVAC element set though is that it assumes ductwork runs only horizontally and vertically. Unfortunately this is not true in real life. For example duct offsets above or below elements are often done with angled elbows and sloped ducts. The reason this is done is to keep the air path as smooth as possible (right angle bends = resistance). Similarly ducts may need to follow a roof profile and therefore be angled. Hopefully NNA will redress this missing capability in the next iteration.

[ 06-03-2005, 12:15 PM: Message edited by: mike m oz ]