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Drawing Perspective
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12-13-2012, 06:41 PM
(12-13-2012, 06:23 PM)jw48 Wrote: Tangent to two ellipses: I had to smile when it was asked if there were any fixes for the AutoCadLT and the only answer that came back was a simple... no. 
12-13-2012, 07:13 PM
I want my money back!... Oh wait! I have Deltacad! Whew....
12-13-2012, 08:03 PM
'The use of vulgarity will cause your post to be ignored and deleted.'
Just noticed The Boss's admonition - and I've mentioned 'A*t*C*d'! Will I be ignored and deleted? John
Once again the "Boss" has given permission for a one time DeltaCad file posting. Thank you Boss!
I've put together a series of Standard Isometric and Isometric in Perspective drawings utilizing squares, rectangles, rounds and the ellipse. They all start with the same isometric axis with perpendicular cross lines to maintain the same distance. There is no text in the file but I hope it's all kind of "self-explanatory". 
Circle Ellipse Comparison Iso Axis.dc (Size: 16.22 KB / Downloads: 26)
I hope everyone can get at least a little information or insight out of the file. williamj Chris, I mentioned earlier about rotating the ellipse 30 degrees to horizontal. Seen by itself the rotated ellipse looks just like a rotated ellipse, but when paired with the two finished rounds, the rotated ellipse takes on the appearance of a round that's just viewed from a slightly different angle. Gotta love optical illusions! Chris, I forgot to mention that I modified your method of using the arcs to get lines to snap to the ellipse. After installing the 100 points in each ellipse, put in a circle arc close to where the lines will attach. At the long ends of the ellipse I was able to put one point of the arc, skip two ellipse points, put the second arc point, skip two more ellipse points and then put in the third arc point. The circular arc still fits neatly into the curvature of the ellipse. No layout line were required. If you want to snap lines to the short axis of the ellipse you can skip three points between arc points and the arc still follows the curvature of the ellipse. I think that by skipping points you get a longer arc and a larger target to attach you lines to. williamj
Its been just a little north of four and a half years since the last post and I really never thought I'd be adding anything more to this thread. But as it turns out I've stumbled on to the easiest to do this yet.
Chris, you were real close with that first illustration you posted. In that illustration the roof is already at an angle. Placing the roof edge parallel with the long wall gives us the opportunity to create story poles. on the long edge of the roof line place a tick mark (point) at every wall element edge. That gives us a horizontal story pole for the length of the building. Do the same for the short wall. At the corner place tick marks at every elevation point, ground level, window bottom, door and window tops as well as at the roof line. Once that is done place your vanishing points and draw a line from bottom building corner to each vanishing point. Select he roof (along with all tick marks), place a rotation point at the corner where all the edges meet (corner, short edge and long edge) . Rotate roof edge to parallel vanishing point line. Place vertical lines, starting at each tick mark, down to ground level. place lines from vanishing point to all tick marks on vertical story pole. Connect cross points between vanishing point lines and vertical lines for all doors, windows and building out line. Rotate roof on corner point to parallel short wall vanishing point line and repeat. If the roof is visible then connect roof lines to establish roof. Erase all lines and your building in perspective is complete with proportionately diminishing lengths and widths. I hope this makes at least a little sense. 
I did a little experimenting with perspectives and the method I used was with a View Point instead of Vanishing Points.
Perspective2.dc (Size: 5.74 KB / Downloads: 14)
Al, I think you just might have nailed it. The only point of view (perspective) that counts is that of the viewer. I have to play with it for a while but I think you've solved the problem of a proportional decrease in the width of wall elements in a building being viewed in perspective.
Excellent work Al, excellent!
After you establish the vanishing points you can draw the tops and bottoms of "windows and doors" on the center vertical line (Point A) then draw lines to the vanishing points.
The sides of the "windows and doors" will still need to be constructed the same way the ends of the walls were made. If the View Point is above or below the "house" (see sample in upper right) I think new top and bottom edges can be drawn from the vertical (Point A) lines to the new vanishing points (which is parallel to the original vanishing point line) then slide (trim) Point B and C vertical lines and the new top and bottom edges to each other. The length of the new Point B and C vertical lines were the same lengths as the original, which surprised me. If there is a round hole it is possible to project multiple points and use a spline to approximate a perspective view of a circle. Notice that I drew 5 arcs (purple) then copied them to the perspective view to transfer them for the 5 X-coordinates of the circle
Perspective3.dc (Size: 3.53 KB / Downloads: 10)
Al,
I haven't "played" with it yet but there's a couple of things that I've noticed. First, (and I'm splitting hairs here) I believe your classification of the horizontal line as a "Vanishing Point Line" is a misnomer, for the simple reason no vanishing points have been established. I believe it's more of a horizontal sight line, a line of sight from left to right at the designated five foot elevation. Secondly, I don't think vanishing points are needed at all. I'm (as I haven't tried it yet) thinking that by extending both roof lines and ground level lines until they cross you will have a point in which to draw your lay out lines for wall element elevations. 1. Establish elevation points of all wall elements on corner A.
2. Establish convergence points (left and right) of roof and ground level lines.
3. Draw guide lines from convergence point to elevation points at corner A.
Doing this for elevation and using your method of establishing width will render a "truer" perspective without vanishing points!
09-04-2017, 10:44 AM
It occurs to me that the convergence points of the roof and ground level lines can be construde as vanishing points.
In a standard perspective drawing the vanishing points are arbitrarally established (at the start of the drawing) by the individual doing the drawing. Whereas with this method, it's the drawing itself that establishes the vanishing points. Thus, making the angle of perspective a better fit for the drawing. |
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