[Blind]

I've been making my way through Ernie Watson's Creative Perspective For Artists And Illustrators, reading a bit and then trying to draw up my own tests for practice. But I'm getting stuck on something, and I was hoping someone could help me understand. On page 40, he uses an example showing how to take some primitives and project them downward. His example has the shape touching the perspective plane when viewed from above, so you can easily determine height with a side elevation. But what I'm getting stuck on is how to do this if the shape were set back from the perspective plane. He mentions that in this example its set on the perspective plane on purpose and that if it were set back you would have to project one of the lines of the primitive down in order to come up with a side elevation. How do you go about doing this?

If I had a scanner I'd post the example for those of you who don't have the book, but...

[atomicmonkey]

You're in luck! I have that awesome book and know what you're talking about.

Here's a image to help explain



Basically you take the height on the picture plane as you already know. This creates AB. Now, take the height of AB and add the vanishing point lines into your picture... when you find where you want to place the building stick it in! (as shown in green).

I realize that was really short but it's pretty simple. Hope you got it.

EDIT: I suppose if you are trying to follow the whole plan, you'd be using the top view as well, and the station point, ect. In this case, you'd place the building on the gound in the picture, and EXTEND the vp line on the ground TOWARD the picture plane, to create B. Using the Height along the side, you can find A. Then once you've found A, you can place the top line towards the vp and thus create the object in perspective, set back in the picture plane.

[ September 17, 2002: Message edited by: atomicmonkey ]

[Blind]

!!Thanks, Atomic!! That does make a good bit more sense now. And yes, I am starting from the top view, setting a station point and then projecting all my lines down. I guess it's the creation of the side elevation that's making me stumble. You see, right now I'm just working with cubes, so if I have a 3cm square representing the cube in my top view, I know the side is 3cm as well. But what if it's not a cube (perhaps I should work with another shape)? The top view tells me nothing of the height when seen through the picture plane. I see how you are getting AB in your image by projecting forward to the picture plane, but starting from the top, how would I know where on the ground to place the object?

On another note: I'm just practicing the instrumental method so I can get a better overall grip on perspective in general. I assume that most people don't actually go to the trouble of laying out all these lines for a simple image unless you're illustrating something that requires that degree of exactness. But I'd still like to have a good working knowledge of how all this is done.

[Ian Jones]

Blind: You would find the position along the receding line by projecting from the top view to the station point / eye and where this line intersects the picture plane you draw vertically down and where that line intersects the receding line you are measureing along you have found your point. With your top view, it should be placed at an appropriate distance from the picture plane, represented here as a straight line as seen from above. Do you work witha top view? well place it at the correct distance you want from the picture plane.

I hope you understood that. Sorry it is a bit of a dogdy explanation and I don;t have time to elaborate anymore..

Hope that helps.

[Blind]

Ian: Yes! I think that makes sense. I need to get home and give it a shot to make sure though. Basically, in the top view I just draw a line from the SP to the line on the primitive, say what AB would be in the pic above if it were against the cube. Where that line intersects the PP I project down, and where that line intersects the receding line from the VP is where the primitive is set back too, right? Hmmm.. ok, I think I get it. I need to get my stuff out tonight and try it. Trying to do it in my head while sitting at my desk is not working, and if my coworkers saw me drawing endless cubes they might start to talk

[ September 18, 2002: Message edited by: Blind ]