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Thread: Spline workaround tip

  1. #1
    All AUGI, all the time AP23's Avatar
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    Default Spline workaround tip

    Splines in Revit work differently than splines in other applications like Autocad or 3ds max. There are 3 major differences:

    1. splines in Revit cannot be trimmed
    2. splines in Revit cannot be extended onces it has been created. Dragging the end points will only scale the created shape.
    3. you can't make end points connect to create a closed loop. This is required if you want to create extrusions, blends etc. Creating a series of arcs to approximate a fluid spline in an extrusion or blend will result into unwanted vertex connection.

    The workaround for number one and two is to export the spline to Autocad or 3ds max. Trim or extend it there and re-import it back into Revit. Once in Revit, you need to explode the spline. Revit will convert it into a Revit splines.

    To create a smooth surface extrusion, blend or sweep from splines, start off in Autocad. Create the spline and make sure it is a closed loop (use the "c" shortcut). Import it into a family or inplace family sketch, Revit will convert the closed polyspline into 2 splines. If necessary, you can modify these splines, just make sure you don't move the endpoints. Once you finish the sketch, Revit will create a smooth surface extrusion, blend or spline with no vertex connection.
    Last edited by Andrew P; 2008-03-21 at 03:07 PM.

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    Revit Mararishi aaronrumple's Avatar
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    Default Re: Spline workaround tip

    Both Revit and AtuoCAD need to improve their spline tools. AutoCAD is FAR better than the almost useless tools in Revit, but it is still lacking in good spline control.

    CorelDraw is probably the best example out there for dealing with spline editing and control. 3DS max isn't bad (but not perfect) so I know Autodesk has the staff to improve these tools in both applications.

  3. #3
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    Default Re: Spline workaround tip

    Revit needs to incorporate NURBs into their list of drawing tools. We require a spline that passes through certain points, rather than a spline generated using floating control points.

    Microstation has excellent curve creation tools.

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    Certified AUGI Addict patricks's Avatar
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    Default Re: Spline workaround tip

    formZ also has quite a few spline creation tools, including NURBs tools. I never really used them much when I was in school, though.

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    All AUGI, all the time AP23's Avatar
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    Default Re: Spline workaround tip

    According to the press release, revit 2010 will get an additional (3d) spline by points tool. However, this might only be available in massing family.
    Last edited by Andrew P; 2009-03-17 at 09:18 PM.

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    Default Re: Spline workaround tip

    I agree the spline tool need to be overhauled. It's ridiculous that if you move the end point the line scales. I can't EVER think of a situation where that would be useful, and not being able to snap to back to the start point. ??????

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    Count (Formula) dbaldacchino's Avatar
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    Default Re: Spline workaround tip

    Quote Originally Posted by djn View Post
    I can't EVER think of a situation where that would be useful, and not being able to snap to back to the start point. ??????
    Funny you should mention that! I was recently building some pendant light fixtures and created the wire as a sweep with a spline as the path, which makes the wire look more realistic. The pendant height is adjustable and the spline ends are locked so the wire adjusts as the pendant length adjusts. There, one good example

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    Default Re: Spline workaround tip

    Quote Originally Posted by dbaldacchino View Post
    Funny you should mention that! I was recently building some pendant light fixtures and created the wire as a sweep with a spline as the path, which makes the wire look more realistic. The pendant height is adjustable and the spline ends are locked so the wire adjusts as the pendant length adjusts. There, one good example
    You actually shed some light on why the spline tool acts the way it does. It seems that they created the tool for use of controlling a spline inside a parametric family. So when your reference planes move back and forth the spline doesn't give some weird results, or you don't have to put in reference planes at every control point. Although I think they took the easy way out. Introducing a scale parameter would have solved this.

    Can you give me an example of where this behavior has been useful when modeling. ie detail lines, model lines, sketch lines, beams, wall ect..

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    All AUGI, all the time Gadget Man's Avatar
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    Default Re: Spline workaround tip

    You can move the end node of a Spline separately - just position your cursor on it and tab it... The second tab gives you the node itself...

    Also, as you move it you can snap it to the end of another line (or any other snap point). So, true, you can't trim it (bugger) but at least you can accurately position the end node on any snap point of another object (i.e. closing the loop). See pictures below.
    Attached Images Attached Images
    Last edited by jetisart; 2009-03-19 at 10:42 PM.

  10. #10
    All AUGI, all the time AP23's Avatar
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    Default Re: Spline workaround tip

    Wow...if i knew this 4 years ago, that would have saved me many headaches and workarounds. Why isn't this documented anywhere?
    Last edited by Andrew P; 2009-03-21 at 09:56 AM.

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