Hi, check out “measuring points in two point perspective”. Once placed on the horizon line, and use in conjunction with the ground line, you’re off to the races… cheers!

Here’s a great opportunity: Bill offering to work up a tutorial for you, zhm.

I realized just now that my answer should read:
“measuring points in one point perspective” as mistakenly, I’d typed “two” point perspective.

But there’s a piece of info missing in your post, you’ve written about a room with an 8 foot ceiling, 20 feet wide, but how long do you want the room to be? That’s critical to implementing the measuring points when drawing in your back wall.

Cheers

I may not have explained the question very well but I think that you have interpreted my question correctly.

After thinking about your response, I still do not believe that one can find the distance from C to A precisely unless one assumes that the room is a perfect square. If so, then I do believe that one can find these distances very simply using geometry (front, back and sidewalls are 20’ in length therefore the center is 10’ from edges. But if the room is not a square then one still does not have any horizontal distance in the picture to scale from using geometry).

I could turn the question around. If we are viewing the drawing here (not the actual setting), and we measure the real distance from C to A then where on the drawing does one accurately place A?

Thank you for your attention and thoughts! Rick

Hi Rick,

That is one application of MPs in one point perspective. Draw the width parallel to the picture plane, then draw the converging lines back to the VP. To create a square (L=W) in perspective we use the MPs to show us where to cut those vanishing lines. I think you’ve done this?

We can also place any distance we like in perspective using the same measuring points. Just count along the groundline/base of the picture plane for the distance we’d like as an off set from the center of vision. Use it like a ruler. Mark that point on the ground line.

From this new point, project/draw it back to the measuring point on the opposite side of the line of sight. Where this new line cuts the convergence line is linear distance we measured out swung around into perspective. (Which converging line are we cutting? The one on the same side as our ground line measuring point.)

Cheers!

I am going to try to post an attachment of a handout I used to give to my oil painting students who were interested in that aspect of perspective–how to calculate the logical, progressive spacing of parallel lines in perspective.

The primary concern is to be able to create a centerline (which is nothing more than a construction line through which you draw projected lines). From then on, it involves the projecting of diagonal lines up to the top, converging line.

Works like a charm. If you have a drawing of a room of given dimensions in feet, merely make tiles, or boards to represent those dimensions. For example, just create 20 spaces to represent 20 feet, in your room.

Thank you very much! This is a helpful method for properly spacing parallel lines towards a vanishing point!

It seems to me that one should be able to simply determine those distances given the 8’x20′ front wall dimensions in the picture and an obvious vanishing point (and without having a known or assumed distance in the z-plane — using the x, y and z notation from which to scale).

Rick

Yes…with the construction of “things” that must maintain a degree of perspective, it is usually the case that the artist (creator of the scene) must first select an initial dimension, or spacing on their own. From that first selection, the remaining elements of perspective can be determined.

I have found that one of the most difficult things to determine whenever I view a rather detailed, or complicated drawing that shows the construction lines, and points, is “What needs to happen first?” In other words, at some point the artist needs to establish SOMETHING upon which all the remaining points of perspective are ultimately based. I have found that very few illustrations of perspective drawing indicate what must be done first.

I’m sure I’ve misunderstood your question.

For the drawing you’ve posted this doesn’t show the front wall of the room which would be critical to simply cutting it in half/quarters etc using Bill’s method along either the side wall or floor. Bill’s is a helpful and much-used method in perspective drawing.

But back to your original question. Even if the front wall were showing, and only the height and width of the front wall known, based on your question how to measure to the points you’ve placed, without knowing the focal length, the distances can’t be determined/reverse engineered.

Bill’s observation that the artist places by judgement/aesthetic a few elements then uses the basics of perspective drawing to complement the desired elements of a composition is also spot on. So, here the first two verticals are drawn in by eye as to distance apart, as the artist would wish, but doesn’t represent any known or inferred distance in your drawing as it’s shown. Matching to the VP does show the same foreshortening, though.

But, we can reverse-engineer distances both relative and absolute from a perspective drawing, so long as enough visual information is given. A neat puzzle with which to play.

Was this a sketch of Sprik’s painting? Perhaps knowing which one might present us with a clue.

Cheers

Thanks to you as well, Rick. Nice puzzle, and I’v learned a new painter, having just looked through Daniel Sprick’s paintings. Wow, a true talent. I specially like his landscapes/urban paintings.