I have been looking at using Inkscape to do some simple isometric drawings directly rather than doing the drawing in a 2D CAD system first. Previously I have imported the CAD drawing into Inkscape (dxf) and then quickly trace over the lines by snapping to the ends. It works fine - I get a lovely drawing, but I'd like to be able to modify the isometric drawing without having to go back and forth.

Here's the thing. Can you type in a line length and angle rather than use the cursor click? You get an angle and length readout at the bottom of the screen, but can you enter numbers by keystrokes?

I understand that Inkscape is not a CAD system, but is this feature already in place? Can I press a hotkey to get access to a precision entry thingummy?

It's not a biggie, but it would save a bit of file juggling.

Thanks

Fizzcat

Hi.

To get exact positions, you can use rectangles.
Draw one, then go to object mode and skew it to 60° -by holding Ctrl, two steps-, then
rotate it 30° -two steps by holding Ctrl.
After that, you can go back to the rectangle tool and type in exact values for the transformed rectangle's height and width.
And use the rectangle's corner as a guide.

Also you can set up an isometric grid in the document settings (Shift+Ctrl+D).

Lazur URH wrote:Hi.

To get exact positions, you can use rectangles.
Draw one, then go to object mode and skew it to 60° -by holding Ctrl, two steps-, then
rotate it 30° -two steps by holding Ctrl.
After that, you can go back to the rectangle tool and type in exact values for the transformed rectangle's height and width.
And use the rectangle's corner as a guide.

Also you can set up an isometric grid in the document settings (Shift+Ctrl+D).

I have just tried this and it is completely brilliant! I had no idea that the rectangle tool would work like that (in hindsight I can see why). I can use the skewed rectangle as a construction tool, position it on one of the corners using snaps and pick up the pen tool and extend the outline around the skewed rectangle. I edit the skewed rectangle for the next bit of outline and position it on the extended outline and go again.

I had sorted out a decent work around since I posted the question last night, but this is way, way better! In fact it is so good I think I can probably dispense with using the CAD for simpler isometric drawings.

Regarding the grid: I've never found isometric grids much use except when teaching school kids about isometric drawing. If you want to draw a real object you end up resizing and repositioning the grid so often it is much simpler in most CAD systems just to specify the length and direction of each line segment.

Many many thanks for that!

Fizzcat

Hi.

To retain the scale when using Lazur's excellent method the object has to be scaled to 86.6025403% ( cos(30°)*100) vertically. This can be done either before or after the Skew / Rotate sequence.

A tip to speed up the workflow is to make "ready-made" objects and just copy the objects, if the squares is kept as squares and circles kept as circles they will scale without the transformation being "destroyed" if you click the squares or circles tool and then scale by using the object handles.

For a brief explanation on using the Scale-Skew-Rotate (SSR) method have a look at my "guide" on Inkscape community forum.

ragstian wrote:Hi.

To retain the scale when using Lazur's excellent method the object has to be scaled to 86.6025403% ( cos(30°)*100) vertically. This can be done either before or after the Skew / Rotate sequence.

A tip to speed up the workflow is to make "ready-made" objects and just copy the objects, if the squares is kept as squares and circles kept as circles they will scale without the transformation being "destroyed" if you click the squares or circles tool and then scale by using the object handles.

For a brief explanation on using the Scale-Skew-Rotate (SSR) method have a look at my "guide" on Inkscape community forum.

Oooh I don't think you have realised just how good Lazur's method is! If you double click on the rectangle you get the rectangle tool up which allows you to type in the height and width of the rectangle. If the rectangle is rotated you get the height and width correctly entered as you would expect, but here's the cool thing: If the rectangle is skewed the height you enter after the rectangle is skewed is transferred to the rectangle as the slant length of the skewed edge! No need for vertical scaling - just enter the length you want!

For isometric drawing I now have a template with three parallelograms: one for xy, xz and yz planes. I can enter in height and width to the relevant one and get the co-ordinate point in the plane relative to one of the corners. I just snap the reference corner to a vertex in the iso drawing and I can snap to the co-ordinate corner. Quick. Accurate. Simple.

I agree about readymade objects. As well as the parallelograms (50% gray 50% transparency so you can see the drawing through the tool) I have isometric ellipses that I can scale to the right size. To make an isometric ellipse you scale a circle vertically by 0.577(or 57.7%). This is the sine of 35deg16min - or the inclination of the isometric planes from the picture plane. (Am I right here?)

You then rotate the ellipse through a whole number of 30 degree rotations until the minor axis of the ellipse is in line with the hole axis and position the hole using one of the parallelogram planes.

This is so cool

Fizzcat

Hi

Oooh I don't think you have realised just how good Lazur's method is! If you double click on the rectangle you get the rectangle tool up which allows you to type in the height and width of the rectangle. If the rectangle is rotated you get the height and width correctly entered as you would expect, but here's the cool thing: If the rectangle is skewed the height you enter after the rectangle is skewed is transferred to the rectangle as the slant length of the skewed edge! No need for vertical scaling - just enter the length you want!

Oh yes I have realized "how good" Lazur's method is. That's the beauty of SVG transforms, and also why you have to keep the rectangles as rectangles (and circles as circles atc.), once converted to paths you will not be able to scale and keep the transforms.
No matter which method you prefer - I reckon it depends on the workflow - when drawing "from scratch" Lazur's method is good - when "converting" an existing 2d drawing to isometric the SSR method might be better - you still have to enter a number "somewhere" - with the the SSR method the scale factor will be "ready to use" after entering once, when entering dimensions the dimensions will have to be entered each time.

To make an isometric ellipse you scale a circle vertically by 0.577(or 57.7%). This is the sine of 35deg16min - or the inclination of the isometric planes from the picture plane. (Am I right here?)

You are right - you will get an ellipse - to make an isometric circle on the other hand you will have to scale vertically by 86.60254% as before. (You might be mixing terms or my understanding is bad. )

Related extension:

https://bugs.launchpad.net/inkscape/+bug/1362534

-and now a bit less related topic:http://www.inkscapeforum.com/viewtopic.php?f=5&t=16307