Descriptive Geometry/Piercing points using rotation

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Piercing points using rotation

If a plane and a line passing through that plane is given, find the piercing point using rotation. Notice that the steps are the same as finding auxiliary views, but rotation allows us to use only the views given.


1) Rotate one of the edges of the plane in top view so it is parallel to the folding line. This will give the true length of the edge in front view.

2) Use the same method of rotation explained in the previous sections. Remember to rotate about one point and remember to always rotate the plane as well as the line.

3) Once the information is carried down to front view, rotate the edge that is now in true length again so it is perpendicular to the folding line.

4) Carry the information back to top view. In top view, the plane should be seen in edge view. The point where the plane in edge view and the line intersect, is the piercing point.

5) Carry the piercing point back to the previous rotated view and include visibility.

(Tip: use different colors for each rotation in order to avoid confusion)


  • Example Problem
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  • Practice Problem
RotationPP2 1.jpg
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