jackamus

I have used Sketchup as a tool for drawing in perspective but it very limited for my requirements. Its OK for large scale architectural type drawing but I wanted to use for technical illustration and it was too cumbersome. I started this thread just asking if scaled drawing could be done in AD and it can't at present so I will continue to use DrawPlus.

I have been working on engineering project in which I use the services of a CAD designer. He uses 'Solidworks' to make a 3D model that I can only view using an 'easm' file reader for checking. Once the 3D model has been OKd he then produces the design in various formats so that it can be made using CNC or laser cutting. He also produces the drawings in pdf for me for editing. This is when I need a graphics program that will allow me to scale the drawing and I have to use DrawPlus to do that or turn the pdf into a jpeg and do it in AD.

You are quite right RC. This is what CAD drawing is all about. However in my case its only a problem if I open a file that contains a drawing that is not 1:1 scale that I want to edit in AD,

So it might just be a matter of changing the DPI. I'll try that thanks. However I'm not always dealing with pdfs. What about a jpeg?

With the greatest respect I do not think you understand what 'drawing to scale' is. I had a pdf file of an engineering drawing that I opened in AD. The dimensions were shown in mm. However, a dimension of 50mm actually scaled at 38mm in AD. If I wanted to edit this file I would have to draw an object of 50mm and enlarge the pdf file until the 38mm dimension matched 50mm. In technical terms this is an enlargement of 1:1.315. In DrawPlus I could just select the 'Scale' feature and enter 50 in one box and 38 in the other box. This would mean that when I drew a box that measured 50mm square , in the real world, it would only be 38mm square in the pdf. If I drew a box 85mm square it would only be 64.6mm square.

Engineers and architects are familiar with using scales. If you want to draw something very large like a house then it makes sense to draw it to a smaller scale. In DrawPlus you choose your scale like letting 1cm on the page represent 1M. This is a reduction of 100:1. Also if you have a drawing produced by someone else in jpeg format and you want to measure it then hen you need to know the scale and set your rule to that scale.

Sorry Guys but I really do mean changing the scale and the units. i.e. I draw a line that is 10cm long but the Transform tab shows 5cm long which is half scale. This AD cannot do. In my view this feature should have been there right from when it was first published and that's why I still use DrawPlus for this kind of work.

You are saying exactly what I thought - I was merely repeating what Uuiop was saying.I couldn't understand what he was trying to tell me. Yes I simply would like to be able to change the scale but AD doesn't have that feature whereas DrawPlus does.

If I have a square shape that is shown in Transform tab as being 10cm square but I want draw another square the same size (10cm square)but only showing 5cm square in the Transform tab. How do I do this?

How do you chnange the dimensions in the Transform tab without it changing the size of the object or shape?

I may have asked this question before but is there a convenient way to draw to a scale in AD like in DrawPlus?

Thank you all for your help.

Sorry - you meant the shapes and not the single stroke.

It was unchecked!

The strokes used in this file for the all the objects is set at 1.5pt yet the single stroke looks twice as thick as the shapes. Why is this? Stroke thickness.afdesign

If you don't believe me then take a photo of a cup or glass, load into AD and check it.

I agree that both the ellipse and the circle obey mathematical equations but the extraordinary coincidence is that if you superimpose an ellipse on that of of a circle in perspective they will coincide exactly. This may be no more than a coincidence but it works!. I think our problem is that I do not see an ellipse as a circle in perspective, which it is, but as a shape that exactly fits a perspective circle and as such it should be possible to do the calculations that I first spoke about. If you simply treat the whole thing as an exercise in geometry i.e. lines and angles then it can be calculated. In my time I have constructed many perspective grids with correctly drawn perspective measuring axes so I do understand what it is I'm suggesting. This has now become a major and a minor challenge for me to solve.

Not so!. As I said the ellipse is a TRUE reprentation of a circle in perspective. If you were to draw two lines at right-angles (diameters) of a circle on top of a square (shown in my file), the diameters will not coincide with the ellipse axes. The ellipse major and minor axes must be confused with the diameters of a circle viewed at an angle. They are merely construction lines. See my attached file. In A and B there is no resemblance between the major and minor axes and the perspective diameters of the original circle in perspective. Ellipses 2 .afdesign

An ellipse is the shape that perfectly describes a 'foreshortened' circle. The major and minor axes of the ellipse is not related to the foreshortened diameter of the circle. The major and minor axes are just construction lines. The attached file shows how the proportion of the ellipse B is changed due to viewing angle. However the file does not show the vertical perspective convergence. I maintain that, after constructing the correct perspective, that this vertical convergence angle is proportional to the viewing angle of ellipse B. In other words the 'thinner' ellipse B is the less the convergence angle will be. If A and B were the same proportion then there would be no vertical convergence. Ellipses .afdesign

A further question. Is there a way to store such a function in AD that I could call upon when needed?

Sorry I didn't realize that this was something I could do in AD. Thanks.

Thanks for understanding what I was getting at. I do see the knock-on effect having to add the Deg box to the Transform Tab and its application to all other shapes and objects. I will just have to produce my own table showing degrees based on major and minor axes. This also creates another interesting aspect from a perspective point of view. As an ellipse goes from a straight line at eye level down to a fatter ellipse at ground level, the major axis will be smaller due to perspective distance. This will produce another vertical angle between the eye level ellipse and the ground level ellipse. I would like to investigate this angular relationship to see if there is calculable.

I realize that but the degree can be calculated from the major and minor axis which is shown in the transform panel. This is just a trig function between the two axes. Also if a degree is entered into the degree box it D can calculate. I would also keep it simple by applying the angle to horizontal ellipses only There's no need to do the same for vertical ellipses as they can be rotated.

When you are doing a technical illustration you may want to alter the proportion of an ellipse to fit the perspective. It is easier, as you progress the illustration, to simply increase or decrease the ellipse proportion in degrees, rather than a difficult to visualize minor axis change. This makes it easier to control the illusion of perspective particularly in an exploded view. Since an ellipse is a circle viewed at an angle it would seem sensible to show that angle as figure in degrees in the Transformation panel.

Sorry I don't follow what you are trying to illustrate. Attached is a file explaining what I meant. Ellipse proportions.afdesign