To represent that or other subject, at first represent its separate elements in the form of the simplest figures, and then their projection is carried out. Creation of a projection is quite often used in descriptive geometry.
It is required to you
- - pencil;
- - compasses;
- - ruler;
- - reference book "Descriptive geometry";
- - elastic band.
Instruction
1. Thoughtfully read objective conditions: for example, the frontal projection of F2 is given. The point of F belonging to it is located on a side surface of a cylinder of rotation. Creation of three projections of a point of F is required. Mentally present how all this has to look then start creation of the image on paper.
2. The cylinder of rotation can be presented in the form of the rotating rectangle, one of the parties of which is accepted to a rotation axis. The second party of a rectangle - opposite to a rotation axis - forms a side surface of a cylinder. Other two parties represent the lower and top basis of a cylinder.
3. In view of the fact that the rotation cylinder surface at creation of the set projections is carried out in the form of the horizontally projecting surface, F1 point projection surely has to coincide with a point of River.
4. Represent F2 point projection: as F is on a frontal surface of a cylinder of rotation, the point of F2 will be F1 point projected on the lower basis.
5. Construct the third projection of a point of F by means of an ordinate axis: postpone on it F3 (this point projection will be located more to the right of z3 axis).