{"id":190,"date":"2025-12-08T16:20:24","date_gmt":"2025-12-08T16:20:24","guid":{"rendered":"https:\/\/www.mywlca.blog\/?p=190"},"modified":"2026-02-10T13:36:42","modified_gmt":"2026-02-10T13:36:42","slug":"project-floor-boundary-on-a-topography-using-dynamo","status":"publish","type":"post","link":"https:\/\/www.mywlca.blog\/?p=190","title":{"rendered":"Project Floor Boundary on a Topography using Dynamo"},"content":{"rendered":"\n
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Final Script<\/figcaption><\/figure>\n\n\n\n
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If you\u2019ve ever tried to project slab boundaries onto a topography in Revit, you already know how deceptively time-consuming it can be. Drawing floors that follow the ground slope \u201cjust right\u201d often turns into hours of manual adjustments.<\/p>\n<\/div>\n\n\n\n

This post walks through a Dynamo workflow that automates the whole process extracting slab boundaries, generating projection points, bouncing them onto the topography and finally recreating floors that follow the terrain. The approach is based on an excellent tutorial by AussieBIMGuru<\/a> (huge thanks!) and simplified wherever possible.<\/p>\n\n\n\n

You will need two free Dynamo packages: SpringNodes<\/strong> and Data-Shapes<\/strong>.<\/p>\n\n\n\n

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1. Extracting the Original Slab Boundaries<\/h2>\n\n\n\n

We start by gathering all the slab or floor elements you want to project onto the topography. Once selected, the goal is to retrieve their boundary curves.<\/p>\n\n\n\n

The Collect.ElementSketch<\/strong> node from SpringNodes<\/em> does exactly this. Feed your slabs into the node and flatten the resulting list, this ensures all boundaries sit in one clean and linear collection of curves.<\/p>\n\n\n\n

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Fetch Floors’ boundaries<\/figcaption><\/figure>\n\n\n\n

2. Dividing the Curves into Points<\/h2>\n\n\n\n

With the boundaries extracted, the next step is to create a set of points that represent each curve\u2019s shape. These points will later be projected onto the topography.<\/p>\n\n\n\n

Convert all boundary curves to nurbs curves<\/strong>
This standardizes the geometry, resulting in a clean list of elements of the same type.<\/p>\n\n\n\n

Determine the number of divisions<\/strong>
Take the curve length and divide it by your desired point spacing (the \u201cdivision length\u201d parameter). Then round the result using Math.Round<\/strong>.
Shorter spacing = more points = higher accuracy.<\/p>\n\n\n\n

Divide the curves<\/strong>
Use the division count to generate the actual points.
After that, extract the endpoints of each divided segment<\/strong>, which will form the basis of our projection onto the terrain.<\/p>\n\n\n\n

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3. Projecting Points onto the Topography<\/h2>\n\n\n\n

Once the points are ready, we need to \u201cdrop\u201d them onto the topography surface.<\/p>\n\n\n\n

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Elevate the points first<\/strong>
To guarantee a successful projection, raise all points along the Z-axis to a safe height\u2014high enough that every point will definitely intersect the terrain when projected downward.
Technically, you can skip this if you always know the correct direction, but raising the points makes the workflow universal and far more reliable.<\/p>\n<\/div>\n\n\n\n

Use the \u201cRayBounce On Link Category\u201d node<\/strong>
From Data-Shapes<\/em>, this node allows you to shoot rays from the elevated points down (or up) toward the topography.<\/p>\n\n\n\n

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Connect the following:<\/strong><\/p>\n\n\n\n