Image of individual basic geometric shapes we studied. The next step should be to study the methods of construction of complex forms of subject, and for this it is necessary first of all to get acquainted with the intersection of at least prismatic, cylindrical and conical shapes together.
Take the simple case where the cylinder intersects the prism.
We have a cylinder that crosses perpendicular to the plane of the middle of the n.
If it is said that in the middle  this means an imaginary axis of the cylinder is a surface plate where it can be drawn a line parallel to the long side of this case, the upper bound and bisect the short side of this face.
Clearly, the intersection of this line and the axis of the cylinder will be the center of the desired circle intersection. We just have to push through the center and the horizontal diameter of the circle with him to repeat the same cuts as the data base of the cylinder. Bottom bracket is formed the same second circle, which we do not build, because it is not visible to us.
Complicate the problem that is not set as the intersection of the middle, and, say, a quarter of the distance from the edge.
Save the main circuit, which started our construction. Find the quarter (right) short of the top edge and draw through it parallel to the longitudinal, then done a same construction as in the previous task  get the circle of intersection. But there is a new  a circle outside the limit of our plates  and this means that the cylinder intersects with it entirely, and part is not crossing.
It is not difficult to guess that, if the cylinder is in the left box (from us) of its part, the right is not he in the bar, and she is in it, and the line of intersection, covering part of the surface of the cylinder, go straight down in order to go to the bottom direction back to surround the cylinder and there, back straight up, connect to the upper circle. In the first case, we have two full circles  each on its side of the plate, here we have a line of intersection, which, if present alone, would have such a form. Such a task can still be complicated by the fact that for some reason we do not see either the top of the cylinder, and therefore do not know and degree of compression of the optic circle intersection and have to find it using the rectangular shape of the face. To do this, some of the upper corner of the rectangle a square building.
