topic Re: API_Gable(Plane coefficients) in Archicad C++ API

API_Gable(Plane coefficients)

Anonymous — Tue, 13 Dec 2022 21:05:59 GMT

Could you please explain the plane coefficients

a, b, c, d - Plane coefficients relative to the parent element.

What is parent element and where is its origin? I mean in which coordinate system the plane is specified.

See GS.APIDevKit.1033/APIDoc/APIHTMLLibrary/Structures/API_Gable.html

Re: API_Gable(Plane coefficients)

Oleg — Fri, 12 Nov 2004 19:18:30 GMT

I never used it therefore I can guess only.
I hope somebody from GS will state it more definitely.

I think a parent element is the cutted element which contains gables array (handle) in the API_ElementMemo structure ( wall, column, object etc ).
And the plane equation coefficients are relative the local coordinate system of this element.
Otherwise I think it would be required to recalculate coefficients at every moving or rotation of the element.

Re: API_Gable(Plane coefficients)

Anonymous — Thu, 18 Nov 2004 23:25:47 GMT

I have used this when getting the planes that represent the top of the wall after it is cut to roof.

To get a point on the plane use this formula:
ax + by +cz + d = 0

ie. plug in x and y and you will get the z value at that coordinate, etc.