How to make a perfect cube in perspective -- does this make sense?
I found a thread on how to create a perfect cube in perspective here: http://conceptart.org/forums/showthr...ng-perspective
The solution proposed in the thread assuredly would work, but seemed really complicated. I figured there had to be an easier way, and it occurred to me that by measuring 1/2 the original vertical line, you could find the point at which the diagonals from the top and bottom of line to their opposite corners would intersect.
This seems to make sense to me, and I can't think of any problems with it, but I wanted to see what other people thought and if anyone could find a hole in my logic. I've included an image to hopefully help clarify the solution:
Ps: sorry if this is in the wrong place, I'm fairly new here.
I'm new here and could always use some advice / criticism. Feel free to take a peak at my sketchbook if you have the time.
How do you determine the angle of the lines you use to locate point C in step 5? Seems to me that depending on the angle of those lines you would get different rectangles and there's no way to determine which angle is the "correct" one that way.
The flaw is in placement of C. There is no way to ensure that the distance from it to AB is correct.
You should simply use the "architect's method" to draw the square base of the cube from its top view. If you search through the forum, you'll find a couple threads dealing with that; or you could get "Perspective Made Easy" by Norling, which also contains an explanation.
The OP is trying to draw a proper cube in 2-pt perspective, not any randomly sized rectanglular block. The OP’s C-point is the center point of any arbitrarily sized rectangle (including a square if you're lucky), as Elwell points out in his example. You're describing an equal spacing technique.
In order to represent a proper cube (essential for drawing proper squares which are essential for drawing proper ellipses for disk or cylindrical things like wheels, building arches, airplane fuselages, coffee cups, etc.), you need to determine the location of the two vertical edges on either side of vertical line AB of the cube as well as the accurate length of AB. AB (in the OP's example) is a line segment on the picture plane (in 2-pt perspective), so it can be measured 1:1 with the cube reference, as in my example (top and left side reference squares).
I know this doesn’t explain things in full, but that’s what all of those books and online resources are for, to walk one through the entire process from beginning to end.