Piercing Points

In this AutoCAD tutorial on Descriptive Geometry, I explain how to find the piercing point—the exact location where a line passes through a plane . I demonstrate two primary methods to solve this type of problem: The Auxiliary View Method: This method involves projecting an auxiliary view where the plane appears as an edge view (a single line) [03:47]. By projecting the line onto this same view, the intersection point is clearly visible [07:07]. I then project this piercing point back to the main views. This technique is also crucial for determining visibility, as I show how to use the intersection point of the line and the plane in one view to determine which object is on top in the adjacent view (e.g., if the plane is hit first, the line is hidden behind it) [02:47]. The Two-View Method: This alternative method avoids creating an auxiliary view. I extend the line in one view until it intersects two edges of the plane [10:40]. These two intersection points are then projected to the adjacent view and connected, creating a reference line that lies on the plane [11:08]. The intersection of this reference line and the original line gives the piercing point [11:44]. I apply both methods to various examples, including a line passing through two connected planes, and briefly introduce a more complex problem of a line passing through a solid object [20:14]. Video Chapters [00:01] Introduction to Piercing Points (Line intersecting a Plane). [01:06] Finding the piercing point in a simple edge view. [02:47] Determining visibility (which object is on top). [03:47] Explaining the need for an Edge View to find the piercing point. [05:26] Reviewing the condition for True Length (parallel to the folding line). [07:07] Finding the piercing point using the Auxiliary View Method. [10:22] Introduction to the Two-View Method for finding the piercing point. [11:44] Finding the piercing point using the Two-View Method. [13:45] Applying the methods to a line passing through two connected planes. [20:14] Introduction to the problem of a line passing through a solid object. [20:53] Setting up a more complex lab problem involving a guy wire on a building.