View Full Version : Rail Extrude with multiple profile curves?

Monster Jack
01 January 2002, 09:16 PM
I'm still learning the modeler in lightwave (have experience with MAX and Rhino). I can't seem to find any info or methods for creating a rail extrude with 2 rail curves and multiple "profile" curves -- surely lightwave can do this simple modeling process - does anyone know how?

Also in another area - is there any type of 3d snap tool?

Any info is much appreciated

- J

01 January 2002, 08:36 PM
Well sorry i cant help with either of your questions....I am a native max user too but I love modeling in lw......I would suggest checking these sites for answers, although some of the tutorials might be a little older they should still be good to get the idea of what your looking for.....or look in the manual and if you lost it or want an online version.......i read that you can download it off of newteks ftp.....but i wasnt able to find if you find it give me a shout..........

Lightwave tutorials on the web ( (

hope these help

Monster Jack
01 January 2002, 09:54 PM

Thanks for your response. You actually can’t do a Rail Extrude with multiple profile curves – I can’t believe it! It’s such a simple and powerful modeling process.

I did figure out how to pull of a similar modeling process though using “MAKE SPLINE PATCH” multiple times – it just doesn’t give you the curve transitions that the multiple profile curves would. Basically it makes you do more work with less precision; hopefully they will fix this in 7.x.

Also, LW evidently does not have a “real” 3d snap tool like the other high-end modelers. Oh well, maybe in 7.x

Don’t get me wrong here, LW is an excellent program – I just think it needs quite a few additions to it, especially in the modeling arena. Specifically in regards to its forte – polygonal modeling. I just wish it had some of the killer poly tools that Mirai and 3ds Max (with the addition of meshtools) have.

- thanks again, anyone else who has any input on this I'd love to hear you're side of things.

Mike RB
01 January 2002, 10:47 PM
monster jack, you can do what you want. I'll post again in about an hour when i get home. no time right now at work.


01 January 2002, 11:19 PM
I just tried using rail extrude with 2 curves and it worked great. Tried a 3 curve rail extrude after that just for giggles and that worked.

I just created a single poly in layer 1 and then created spline curves with each in its own layer.
Select layer 1 and have the spline layers selected as background layers and apply the rail extrude plugin.

Make sure the spline rails are lined up on one of the polygons points or else it won't work as advertised.

You can also use just a spline curve in place of the polygon extrude shape in layer 1. Since I was after some pretty simple geomtry that I could use as a subdivision surface I just created a flat square polygon for my extrude shape. I later just changed the square poly shape to a spline by using the "k" command to kill the poly and leave the points. I then used those points to create the spline. (command ^P after selecting the points in sequence.)

Mike RB
01 January 2002, 11:39 PM
Chewey beat me on that one. Follow what hes says.


01 January 2002, 08:50 AM
hmm I have to say this feature can rally be useful and the fact that you're totally free in how to use it or how many splines / rails to use makes it even more powerful.

Monster Jack
01 January 2002, 12:59 AM
Ok, I think I have tried every possible variation for creating a rail extrude with more than 3 total curves. I must not be understanding something simple here. I have been able to easily and succesfully create rail extrudes with 1 profile curve and 2 rail curves but cannot with more than 1 profile curve - I've tried every variation of background foreground layer combos I can think of.

(btw - thanks for all your insight guys)

Below is a screenshot of what I can't get to work:

Below is an example that I did in Rhino (stand alone NURBS modeler) 4 curves were used to create this surface:


01 January 2002, 12:33 PM
with what you have there in the lightwave interface, i 'd suggest using Patches to construct that shape.

just bring all 4 profiles on to the same layer and select them all and ^F (ctrl-F) those bad boys.

that would be my newbie to modeler suggestion.


-p o l i c a r p o

here's a sample: it might not be right...but hey...i'm learning too.


Mike RB
01 January 2002, 12:48 PM
also, if have all your curves on one layer and do the patching operation with that layer and another selected, it will put the new polys on the second layer for you.


01 January 2002, 01:07 PM
suweet...thanks for that pointer...

- p o l i c a r p o

Monster Jack
01 January 2002, 04:38 PM
Policarpo, Mike, thanks for the suggestions. Spline Patches will work if you are only using *4* total curves that have their beginning and end points welded (or merged).

My question about modeler's capability was simplified - I actually want the freedom of using as many curves as necessary to create a single complex organic surface with this method. I can easily do this with other modelers (I mean really easily).

Spline Patches are the only way I can find in LW to get around this. The primary problem with spline patches replacing the multi-curved rail extrude is that you are limited to 4 curves per patch - so you have to section your surface up into 4 curved segments and convert them into patches from there.

Basically, it'll just take me way longer per surface and it will be more difficult to maintain the same level of accuracy.

That's the first big shortcoming I have found in LW, hopefully one of the last - oh well.

thanks again guys,

01 January 2002, 04:41 PM
you could always just do that sort of modeling in rhino and import the OBJ into lightwave for final rendering.

sometimes you just have to use the tools that you are most comfortable with in order to get the job done.

as with life, there are weaknesses and strengths with each package.

if you find a way around this, please be sure to let me know.

good luck!

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