descriptive geometry

[amitseg]

Hey everyone,

I hope that I will find the right answer here:

attached here an image of front (the upper) view and top (the lower) view of some shape (I am working according to the first angle projection). my question is - what is the method for finding the third view (the side view). is there any general method to solve this kind pf problems? I kow that I should draw a 45 deg line, but from there - how do I know whice points in the known views corresponds to the points in the unknown view?

thank you so much!

new doc 2018-07-20 00.40.38-20180720004046.pdf

[Frank]

Homework?

Orthographic projection - Wikipedia:  https://en.wikipedia.org/wiki/Orthographic_projection

 

First Angle Orthographic Projection:  http://www.technologystudent.com/designpro/ortho1.htm

 

[Bender]

There are a limited number of possibilities to choose from:

- point in one view is point in other: will be point in third and you have all coordinates

- point in one view is line in other: will be line in third view. Since it is perpendicular to the first view, length of the line is known

- line in one view is line in other: must be line in third. Coordinates of each end point can be determined  (see option one)

- line in one view is plane in other and line is in one of the principal directions: will be line in third. Length and position are known.

- line in one view is plane in other, and line is slanted: must be plane in third. The plane must have the same shape as in the known view, but scaled in one direction.

- plane in both views: plane or line in third view. The planes must have the same shape, but scaled. Each vertex  (point) of the plane can be projected to the third, where it will be a line or plane with the same but scaled shape.

So the tricky part is finding the corresponding points/lines/planes. With practice, you can imagine what the shape is in 3D, and it all becomes easy. Before you reach that point, start with the planes: are there corresponding lines/planes with the same width/height?

Important is that you can do this exercise for individual points, lines and planes first. There is no point in trying a 3D shape if you cannot project the constituents correctly.