fundamentals of descriptive geometry
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Fundamentals of Descriptive Geometry. Department of Applied Technology And Technology Management September 9, 2013. Point View of a Line. What you see when you look down the length of a line. Experiment: - PowerPoint PPT PresentationTRANSCRIPT
Fundamentals of Descriptive Geometry
Department of Applied Technology And Technology Management
September 9, 2013
Point View of a Line
• What you see when you look down the length of a line.
• Experiment:– Take a pencil and
look at it from various directions, keeping in mind the rotations between line of sight directions.
Principles of Descriptive Geometry Rule #2
If the line of sight is parallel to a true-length line, the line will appear as a
point view in the adjacent view.
CorollaryAny adjacent view of a point of view of
a line will show the true length of the line.
Points on a Line
• If a point is on a line, it will appear on the line in all views and be at the same location on the line.
Not All Points that APPEAR to be on a Line actually are!
• Two orthographic views are required to see where any given point lies.
Planes
• Planes are surfaces that can be uniquely defined by:– Three non-linear points in space,– Two non-parallel intersecting vectors,– Two parallel vectors, or– A line and point not on the line.
Plane Definitions
Plane Classifications
• Planes are classified as– Horizontal– Vertical
• Profile• Frontal
– Inclined (perpendicular to a principle plane)– Oblique (not perpendicular to a principle
plane)• Horizontal and Vertical planes are principle
planes.
Examples
• Orthographic representations of planes as they appear in the principle views
Principles of Descriptive Geometry Rule #3
Planar surfaces of any shape always appear either as
edges or as surfaces of similar
configuration
Principles of Descriptive Geometry Rule #4
If a line in a plane appears as a point, the plane appears as
an edge
Principles of Descriptive Geometry Rule #5
A true-size plane must be perpendicular to the line of sight and must appear as an edge in all adjacent views.
Drawing a Plane in Edge View
A Corollary to Rule #5
If a plane is true-size then all lines in the plane are true
length and all angles are true.
Finding the Angle Between Two Intersecting Planes
• The key is to create a view where BOTH planes are in edge view.– The common line between the planes is the
intersecting line. – Create a view where the intersecting line
appears as a point.• Start by drawing a view of the line in true length• Then draw the desired view.
Finding an Angle
