Wednesday, May 30, 2012

HIGHWAY TO HELL

Just for the record I'm not a big ACDC fan, but I've been developing some approaches to roads and paths that wind their way around a mountainside over the past couple of months.  One or two challenges on the way.


The first attempt was based on the idea of circles in plan that guide the spacing of points and dropping down from these points one metre at a time to give path gradients of 1:10, 1:20 etc depending on the diameter of the circles.



It's an adaptive component. A rectangular profile hosted on the lower point sets the width & depth of the path.  You can adjust the points directly in the project to make the road/path snake around the contours.  I made a pad to cut a channel through the mountain for my snake to rest in.


The sketch of the pad uses splines so I can adjust the edges of the cut, then painstakingly create bits of topography to simulate cut and fill slopes.  I was helping a design team to study alternative routes for an entrance road and get some feedback on how this impacted on the mountainside.  By the time we reached option 4, we needed more points and I decided to try a different, looser approach, just modelling directly in place.  Still massing, but just setting up a 3d spline by points, then hosting points on that and adding profiles as needed.



One of the challenges was how to keep the road from twisting.  This is where the title comes from.  Minor adjustments are fine, but if you make a major change to the route, the road starts to lurch around like a drunken man.


You can fix this by selecting the profiles one by one and rotating them back to a more horizontal position.  It's almost as painful as the point-by-point adjustment needed for the topography.  Roll on better site tools.  (We live in hope)  But we got what we needed from the exercise and I learnt some important lessons along the way (as usual).



That was 3 or 4 weeks ago.  Now we have to create a network of paths within the site itself and linking together the various elements within the resort.  So I wanted to come up with plan C that would have the freedom to add more points easily and also keep the path perfectly level during the adjustment process.



So I am starting with an in-place mass, setting the work plane to zero (sea level in this case) and drawing a spline.  Then I host points on the spline and change their "measurement type" parameter to "segment length"  This gives me a string of beads spaced at regular distances along a freely adjustable path.




Next step is to select all the points and change "show reference plane" to "always".   This allows me to  place a profile family on each point.  Then select all the profiles and "create form" 


Because all the points lie on a level plane, their reference planes will not twist when the path is adjusted.  So my profiles remain level, and an instance parameter allows me to set the height above sea level. 



Now I am in business.  I can adjust the centreline of my path in a plan view with the countours of the site visible.  I have points at regular distances (say every 10m) and I can set the height of the path at each and every point.  The profiles will always be at right angles to the centre line and remain level.  If I want a 2% cross-fall then I can build that into the profile family which is a based on a Mass template and set up very simply in a plan view.



I'm very happy with the result.  Next step is to start placing these on the site.



And here's a link to the download  "key to the highway"

8 comments:

  1. great post! always had the problem with the twist profiles. the main key is to select only the profile to make the form and leave the path behind.....I will test this ASAP. thanks!

    ReplyDelete
  2. great post! always had the problem with the twist profiles. the main key is to select only the profile to make the form and leave the path behind.....I will test this ASAP. thanks!

    ReplyDelete
  3. great post! always had the problem with the twist profiles. the main key is to select only the profile to make the form and leave the path behind.....I will test this ASAP. thanks!

    ReplyDelete
  4. About 2 paragraphs into your post I was screaming Civil3d! You could have made a thousand options in the same time. There is no way to trust Revit topography

    ReplyDelete
  5. Thanks for the comment, and for making me wonder yet once more whether civil3d is "something to have". Unfortunately I don't have access to civil3d & I've never used it. Does it play nicely with Revit ? Lots of interesting questions here.

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  6. Hi, can you explain how to create "measurement type" parameter ?

    Tks

    ReplyDelete

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