[Jorge]

I am trying to do the cubes exercises proposed by Fred ages ago. When I thought about perspective cubes, I thought, bah, child's play, and about after two seconds trying I had to dig through the archives to know how to get 2 perspectives cubes with perfect proportions (the projecting system).

Now I had to do a cylinder in perspective. Bah, child's play... Oh, oh... How the heck do I project a top view of a cylinder into a perspective view? I think I figured out the width of it (tracing tangent lines to the circle from the POV?), but I do not know how to determine the depth of the ellipses, which I think might be related by the fact that I do not know how to find a VP for the cyl either.

Francis, if you are reading, your schemes on projecting where very useful. Could you (or whoever) explain this to me, please?

[Krztfr]

How i would personally do it. would be to draw a perspective cube, and then draw the ellipse touching each side of the cube. If you can get what im getting at. It gets pretty good accuracy, for a semi eyeball approach.

IUmm i dont know how to explain this better.

At the top of your box in perspectice, draw a curve from each side of the box, so it creates an ellipse.

Hope this helps.

[Jorge]

Yes, that is what I tried first, but try to draw an ellipse in the projected square. you'll notice it is not that easy. To figure out better what I mean place the POV real close so that the perspective is exaggerated a lot.

[Jorge]

Just in case people who could answer did not notice the post, let's bring it to the top ^_^

To expand on it a little bit, my cylinder is not in the exact center of the scene, but a little to the right. At first I thought ellipses coming from circles in perspective should always be 0� rotated, but now I see rotating my ellipse a bit as the only way to get it right, but still, I have to eyeball a bit. There must be a way to get this exact without eyeballing, no?

[Fred Flick Stone]

Jorge-

I knocked this out very quickly, I apologize for not using the same sample for all the steps.

As for really up close POV's, the same rules apply. YOu have to complete the entire cylinder from off camera, or overdraw, so that you end up cropping the cylinder down the way they would look from whatever POV you are viewing it from up close.

The thing you have to remember is that the cylinder is not going to look like a cylinder on an ellipse guide. Those are very mechanical, for mechanincal drawing, where objects really need to be drawn out accurately for the production guys to build the drawings.
What you are doing is illustrating a cylinder into a field of view with other objects: a scene. With true perspective at work, the roundness of your base circle is not going to be totally equal in all four of its divisible four quadrants. There is going to be some awkwardness in its skewing. Do not be alarmed at this, this is perspective at work, fooling you into thinking you did not make a clean cylinder. Just the opposite in fact, you have done it right, it just looks a bit strange till you shade it to the correct lighting, then it should start to read as a convincing cylinder in 3 D space.
Hope this helps you a bit, if you have any further questions, email me or post here and I will try and better explain what you might not be getting correct. Good luck with your drawing...

[Jorge]

quote

Quote:

As for really up close POV's, the same rules apply. You have to complete the entire cylinder from off camera, or overdraw, so that you end up cropping the cylinder down the way they would look from whatever POV you are viewing it from up close.

I did not quite understand anything from that paragraph. Still I understood the basics. I was expecting to have to fit an ellipse in the projected square and obviously I was having lots of problems. So a certain amount of eyeballing is the way to go.

I'll get my black and white boxes and cylinders up really soon. Just in case anyone feels curious, first exercise is here. (Note there is a 1st and a 2nd attempt!)

Fred and every soul there, thanks a lot for the feedback and every second you spend trying to teach others beatiful things.

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Jorge

[This message has been edited by Jorge (edited September 04, 2000).]