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3D rails

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i'm struggling yet again to get my head around VW 3d, which has got to be the most perverse system i've come up against...

i don't like the handrails in the stair tool, so i trace the shape with a 3d poly, go back to plan, draw a rectangle as the section shape, select both + extrude along path... and get ... failed due to invalid path or profile....


change rectangle to 3d poly, no luck,

change 3d polys to nurbs, no luck,

etc etc...

what am i missing? how hard can it be to extrude along a rail?

any help would be gratefully accepted

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that's right, but it defeats the point of trying to make a 3d handrail if you're forced to use a 2d path...

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Yes. But not entirely. You can still make the object (either using this method or with simple extrudes) but then you would need to rotate and trim (subtract from) each piece. If you're doing serious (and detailed) modeling where the close up view is important then you just gotta do what you gotta do. If not, then why bother?

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The extrude along path Path object does not have to be a poly or 2D.

It works with a non planar Nurbs path or 3d Polys, open or closed, filled or unfilled.

Something else is wrong.

Try putting just the path and the profile in a new file and see if it works.

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Working with a group ... set the NURBS Path to match the 3D view... then create the 2D profile in the perpendicular 3d view ... convert to NURBS ...select all and Extrude Along Path.

Then it may be necessary to edit the profile location on the path >enter the new Extruded group >edit profile.

It takes a little practice but only 5 or 6 steps to get what you need.

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i've discovered LOFT SURFACE with ONE RAIL

does the job perfectly, but having just

read yours + islandmon's mails + tried

in a fresh file...

draw 2d poly, L shaped with point along

the length to mark the landing;

convert to 3d poly + raise landing

portion in side elevation;

draw 2d poly for rail section in

side elevation;

try extrude 3d poly path + 2d poly

profile = FAIL....

really irritating, but after a couple

of tries i have discovered that it is

editing the 3D poly that causes the failure.

don't lift the landing portion + it works fine.

surely this is a bug? then i tried tracing the

'modified' rail 3d poly, so that it would be an

'unmodified' 3d poly. still FAIL...

this also failed with all combinations of 3d

polys + nurbs curves as rails +/or profiles...

if the 3d polys + nurbs are drawn 'flat' they

work fine, but if they are drawn "3d" or

edited into "3d" after extrusion they fail...

maybe the tool is, or i am, broken.

maybe my expectations are wrong?

in microstation you can extrude any profile

along any path, along any 3d route, so that

is how i understand "extrude".

is VW extrude just along a single plane?

i'll stick to LOFT...

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I just tried again and had some failures, but I also tried with a definitely non-planar NURBS curve and it definitely worked.

When I converted the NURBS Verticies to "corner" verticies it failed.

Perhaps Biplab can clarify things here?

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on your example image; how did you make the inner handrail?

was it extruded along one continuous rail?

if so, could you please give me an idea of how you managed it?

<if you've got the time?>

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The inner rails are a reflection of the outer rails ( trimmed @ inner end ) + a simple "U" shaped ExtrudeAlongPath of the rail profile.

It's easiest to model 'switch-back" dihedral curves with 3 parts instead of a single NURBS curve.

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thanks for the explanation,

i think the LOFT tool is what i should stick with

for continuous "extrusions"

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Would'nt it be nice if 'creation failed due to invalid path or profile objects' fail message continued with 'try loft with one rail'. I created in plan view a u shaped 2d poly, converted to nurbs; moved vertices to desired elevation; changed to front view; drew 2d rectangle and a circle; tried rectangle...fail. tried circle success. go figure.

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it seems like the extrude tool really is stuffed.

i tried fred's example,

extrude works with circle along nurbs rail,

but not with a rectangle,

or a rectangle converted to a polygon,

or a polygon drawn as a rectangle,

or as a polyline drawn as a rectangle,

or a poly* as any other shape,

or an oval...

nothing but a circle....


that if you duplicate the rail, it fails

if you use a circle drawn BEFORE the rail

was duplicated, but works fine if you use

a circle drawn AFTER the duplication of the


in addition, having extruded the rail from

the circle + then edit the profile, all you

can do is change the diameter of the circle,

any change to the type of object used as profile,

or even moving the circle, causes the failure


can anyone else confirm this weirdness?

can we have a new extrude tool please?

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I tried FredM's problem as well with the same outcome. Tried making the profile a nurb as well but no joy. Definitely an issue here. As soon as the path has a 3D component in it the profile has to be a circle for it to work, Even an oval won't work.

One intriguing thing I noticed is that you can move the Nurb path vertices in the Z direction with the 3D Reshape Tool when the profile is a circle, but not if it is anything else.

Something must have changed in VW 12. The extrude along path road example in this thread was done in VW 11 and it has a rise component in its nurb path. http://architoshforums.forest.net/showthread.php?t=1307

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I have just converted the original VW 11 'road' drawing to a VW 12 drawing and I can change the Nurbs vertices and it is fine - both by editing the nurbs path and by using the 3D Reshape Tool. Go figure that one out.


I have figured it out. If the vertex is a corner it won't work. Change the corners to an arc , bezier or cubic spline point and it will work with all shapes. If you have a corner point it will only work with a circle.

So now you know.

Edited by mike m oz

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