Coordinate systems

Hello, I admit that I found a number of similar posts regarding “project coordinates”, but maybe it’s my lack of understanding - in which case I would be grateful for an explanation or I am overlooking something.

I have a Revit Project in which I took some Spot Coordinates to use as Setting Out points for a conceptual mass to be build in Dynamo.

I then had the idea to create points in Dynamo using the X and Y coordinates. Note that I had intended to place the mass later manually. I was not expecting it to “fall” into the right place automatically. However I thought that the relative position of those Dynamo Points should surely reflect the position in Revit.

Too my surprise however, the points appear to be “flipped” or “mirrored” on the X/Y plane somehow. Z direction appears to be “up”, as that is what I see in the Mass Family in Revit.

Could someone explain to me why that is? Could it be related to the Project North Rotation and how could I fix it? Apologies if I overlooked an explanation somewhere else, but all help is very much appreciated. Thanks.


Points in Dynamo are based on the internal project origin - the hard coded XYZ vectors and global 0,0,0 point, none of which are ever really exposed. You have to translate your values from the project coordinates to the global origin values to use the method you are proposing, which can be difficult.

A better method for this exercise might be to use a select edges node to allow you to select the curves which define (what I assume) the polycurve that will make up the limits of your mass.

Thanks @jacob.small. I thought that within to coordinate systems, relative “constellations” of points should result in the same geometry, independently of the rotation of the entire coordinate system.

The problem I have with selecting edges is that the Dynamo Script is supposed to point to a Conceptual Mass and the edges would be in the Revit project file as well as a linked surveyor’s model.

better late then never… here is a blog post for the coordinate systems


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