Making a perspective drawing  part 3
Perspective: Seeing where you stand
Carrying on from Part Two
Now to make a sphere:
Do you remember the plan of the circle you drew in steps 10 & 11? Like most plans, it represents a view of a circle from above, just like looking at a map. But a sphere looks like a circle from any angle, so this could also be a view of a sphere from the side.
Now think of this: if you cut a slice straight through a circle at any point the flat cut will always be a circle. The only difference (depending on where you make your cut) will be the size of this circle  its diameter (this is like imagining a sphere inside a tower block. On each floor the diameter of the section will be different)
21. Look again at your circle plan, but this time, imagine it is a plan of a sphere from the side. Can you see that this plan crosses each of the horizontal lines of the grid?  One point on the left side and one on the right.
Draw a line the same width as the two points where the circle crosses each of the horizontal lines. This is the width (diameter) of an imaginary slice through the sphere at each of these levels. So if the sections of the sphere have different diameters at each level, by making a circle the same size and putting it on its own horizontal grid, you will end up with a set of circular slices that make up a sphere. How? 



22. Draw a vertical line up the middle of your grid. Now draw a point on the centre horizontal line the same width from the centre vertical as each of one of the end points of the diameter lines  


23. These dots are the radii of your circle slices, so take a pair of compasses and draw them in!
Tip: You only need new circles for the horizontal grids up to the middle line, because the top half will be identical to the bottom half 



24. Just in the same way that you plotted a circle on the base grid of your drawing, look at each point of each new circle where it crosses and make a dot on the relevant grid in your picture. Don't forget which grid level your circle belongs to! The bottom one will be just a dot, then the smallest actual circle will belong to level 2, the next smallest to level 3 and so on.  


25. If you want, and you can still see your drawing for the web of lines, you can put in the vertical slices too. To do this just follow the same procedure, but plot the circles on your plan onto the appropriate vertical grids.  


26. If you want to put in circles facing directly towards you its easy  because they will still be circles. But don't forget that the biggest one will be half way back on any grid so it will look a bit smaller than on your plan.
You can now draw anything using this system of perspective, as long as you have the patience. But patience is a problem (as well as all those lines). Imagine you wanted to draw a person, or a face? Well you could, but drawing them slicebyslice would take years. This is why the drawing machine was invented. 