Drawing Perspective

[williamj]

At present, two procedures for

[i44troll]

Quote: If, for instance. Fractional units of measure were required then the first foreshortened line would, of necessity, have to be in that fractional unit of measure.

Not necessarily Bill,

Remember that the first distance is not an actual given measurement but just an arbitrary distance that looks good to the person drawing the scene. smaller segments can be laid out as long as they "appear" to be laid out in close proximity to those invisible diminishing fractional units. Since NO line can actually be dimensioned properly it would be impossible to judge whether a draftsman used smaller fractional units or not. Still, we can always make better judgments in location if we have graduation marks that offer us better focus and orientation when drawing in perspective.

Chris

[williamj]

Quote:Remember that the first distance is not an actual given measurement but just an arbitrary distance that looks good to the person drawing the scene. smaller segments can be laid out as long as they "appear" to be laid out in close proximity to those invisible diminishing fractional units.

I would agree if we were creating a free hand sketch or a paintning but in dimensioned or measured works, I believe, there must be some consistant relationship between measurements.

If (in the attachment below) the left window were located at 8.5 units of measure instead of at 9 units of measure, the foreshortened location of the window would not proportionately be at foreshortened line 9 but somewhere between foreshortened lines 8 and 9. And , to my mind's eye, the left window would appear out of place in the finished drawing.

   

Quote:Since NO line can actually be dimensioned properly it would be impossible to judge whether a draftsman used smaller fractional units or not.

It's not a matter of being able judge or discern actual measurements, I believe, it's a matter of what the eyes sees as appropriate or "inbalance" (for lack of another word). To arbitrarily place a window or door on a foreshortened line would, in effect, place it out of position in the finished prespective drawing and the human eye would easialy be able to see it almost imediately.

just some more of my two cents (if I keep this up I'm gonna hafta hit the piggy bank for more two centses)
williamj

[williamj]

I see by the "View Count" that there is conciderable intrest in this thread. What would be nice to see as well is more member participation. We need more members to, not only try these procedures but to come back and say.. "It worked.", "It didn't work." It worked but... .

By tearing it apart and then putting it all back to gether again we can end up with a "more better" solution to what ever it was that we were trying to do in the firsst place. (I think)

So get in there and try this stuff out and tell us... "It worked", "It didn't work." or "We need to do 'this' or something like 'this' to get it to work better."

williamj

[williamj]

Clive,

Thanks for the responce.

If I've learned nothing else from this I've learned that "Perspective" is not one thing and only one thing. Perspective truely is as varied as there are people who have a point of view. Kind of like beauty, it's all in the eye of the beholder.

I'm trying to work something up that will illustrate that but it's a slow go for some reason. May take some time but when it's done I'll post it.

williamj

[williamj]

(09-09-2012, 12:45 PM)williamj Wrote: I'm trying to work something up that will illustrate that but it's a slow go for some reason. May take some time but when it's done I'll post it.

Okay, finally got it figured out. To get a properly proportional (proportional to a particular point of view) perspective you have to have two different points of view.
Proper proportioning isn't just a matter of left to right consideration but of from front to back as well. It's the front to back consideration that make it all proportional.
It definately took some time to get it all figured out but I believe that the results offer the most accurate of perspective illustration.

I'm just now trying to figure out how to put it all down on paper (as it were). So I'll be back when that's accomplished.

williamj

[williamj]

Chris,

The very first image you attached in Post#2 is so amazingly close to the final (atleast "my" final product) product. The topographical view is the "second" point of view I was refering to in my last post.

Instead of the dementional lines going just going straight down they must instead radiate back to the point of origin, the first "point of view" (as shown in attachmentone).

   

The closer the vectors get to the "point of origin" the closer the they come to one another proportionately deminishing the width as it goes.

Now comes the part that was very elusive to say the least.

When looking at a drawing on a piece of paper what we are actually seeing is the "surface" of the piece of paper that the image is drawn on. It is this surface that determines the final deminished dimension. Keeping it as simple as possible I just placed a terminating line at the point where the object comes closet to the origin (as shown in attachment two).

   

Where the vectors and the terminating line intersects place new temproary basepoints, highlighting the new anchor basepoint for easier placement later. The terminating line with the new basepoints become a horizontal story pole to deliniate the horizontal dimensions in the finished drawing.

Place the horizontal story pole, paying attention to proper alignment (as shown in attachment three).

   

From the base[oints on the horizontal story pole draw vertical lines up intersecting the vanishing point vectors (as shown in attachment four).

   

All that remains is to draw appropriate shapes at the intesections of the appropriate vectors (as shown in attachment five). Attachment five also show actual proportional diminshment in demensions.

   

my head hurts,
williamj

[williamj]

In reviewing this thread, I noticed that Isometric drawing was briefly mentioned, and it got me to thinking. I don't ever recall seeing an Isometric done in Perspective, atleast I've never seen a technical Isometric drawing done in perspective. So I figured, why not? After working with it a little, I was surprised to find that it wasn't difficult at all.

The attachment shows a standard Isometric view, as well as an Isometric view in Perspective and just how easily it's done.

In Standard Isometric it starts with an Isometric axis drawn at 30 degrees from horizontal. A perpendicular line is then added and then paralelled some distance away.Two circles are then added along with two lines defining the boundary of the cylinder. The far circle is now split at the junction of the sides and the bottom half deleted. All line and arc ends are then merged and axis and perpendicular lines are erased. The Standard Isometric drawing is now complete.

Isometric in Perspective varies only slightly from the Standard Isometric. Starting again with an Isometric axis, perpendicular lines and circle the Isometric axis is extended some distance, and the end of that extended axis now becomes the vanishing point of the drawing. A vanishing point vector line is drawn from the vanishing point back to the circle perimeter as shown. A smaller circle is now drawn from the junction of the second perpendicular line and the Isometric axis expanding out to the intersection of the vanishing point vector line and the second perpendicular line. The cylinder side boundary line is now drawn following the vanishing point vector line starting at the first circle to the second and smaller circle. This side boundary line is now mirrored using the axis as the pivot of that process. The smaller circle is now split at the boundary line intersections and the lower portion deleted. Boundary lines and arc ends are now merged and all guide and axis lines are erased.

And there it is, an Isometric drawing in Perspective.

just thought I'd share,
williamj

   



I'm back

Playing with it a little more, it is obvious that a square or rectangular shapes needs to be handled a little differently than circular shapes (need to play with ovals and see if that changes anything).

As shown in the second attachment a second intersecting line (blue) going from corner to corner in the square (rectangle) is drawn and then placed at the intersection of the second perpendicular line and the Isometric axis. Using the center to corner shape tool a square (rectangular) shape is then drawn from the intersection at the second set of intersecting lines out to the vanishing point vector and the corner to corner intersecting line (blue). After the second square (rectangular) shape is inserted everything else is pretty much the same as in the circular shape in the previous attachment.

williamj

   


I'm back again,

Just played with the oval a little bit and I gotta tell ya... this is gonna be a trip. For some reason the oval has chosen to be quite difficult. Will be back when I get a better handle on it.

williamj

[williamj]

I'm having some difficulties in finishing this. Mostly it has to do with the way DeltaCad works (or doesn't, in this instance).

When working with circles and lines, lines of the "draw a line with two end points" variety, the lines usually "snap to" the circle. But for some reason lines of the "draw a line with two end points" variety do not snap to an ellipse. Without this "snap to" feature it is extremely difficult to draw the defining side lines of an elliptical cylinder. The placement of the end points always seem to be "just a little" bit off.

any suggestions?
williamj

[i44troll]

Bill, give us a sample drawing. I think I know what you're wanting but I'm not 100% sure.