Take the 2-minute tour ×
Graphic Design Stack Exchange is a question and answer site for Graphic Design professionals, students, and enthusiasts. It's 100% free, no registration required.

Say I'd like to produce the following diagram in Inkscape.

additive color diagram (RGB)

How were I to proceed? I can create three overlapping circles and I can create intersection objects from them but the problem is to align the intersection objects with the original circles. When I copy the three circles and paste them again, they turn up anywhere on the page and not in their original spot. It's very hard and in fact practically impossible to exactly realign the four intersection objects because even the slightest mismatch will create something like color fringing.


Edit: This is what I actually need and what I got so far with manual placement:

Big Euler Diagram

To be honest, the upper right intersection element is only darker than the other two because somehow I didn't get it to be bright. Maybe it's because of the gradients in the circles or maybe just because I don't have a very good mental model of what the overlays do.

share|improve this question

2 Answers 2

up vote 3 down vote accepted

An alternative approach would be to create the three circles as separate layers. Position the layers so they intersect as required and use blending mode 'Screen'. This will give you the color mixing that you show in your example. To make the background black you can fill the remainder of the page of create another layer, fill it with black and move it to the bottom of the stack.

There is another method to create the intersecting areas that will be more suited to your drawing.

  1. Shift select the three circles.
  2. Ctrl-D to duplicate the circles (they will appear right on top).
  3. Shift select two circles at a time and do Path -> Intersection. This is display the intersection area between the two circles. Select whatever color you like.

In your case you'll need to repeat step 2 thrice, since you need to get three, 2-circle intersection areas. To get the intersection area at the center, shift select the three 2-circle intersections you just created, Ctrl-D, then Path -> Intersection.

share|improve this answer
    
Wow, I didn't realize that screen does exactly that. Otherwise I would have added that I don't actually use the colors show in the example picture but a much more complicated arrangement. I want to create an Euler diagram with half a dozen ellipses overlapping and text also being in the mix. I do use screen but it gets illegible at some point. Sorry for not making that clear in the question :/ –  Christian Nov 16 '12 at 8:27
    
Not exactly sure how you place your text. If you place all your text in a separate layer does that still make the text illegible. If possible update the original post with an example of what you're looking for and we'll take a look again. –  dinesh Nov 16 '12 at 9:03
    
Ok, I just added a picture of what I got so far. You can't see the mismatch in this resolution but I'm afraid in print or when zooming in in the PDF, it will show. The blue/yellow is the color scheme, all the other colors are just a result of me fumbling with overlays to get something readable. So if these colors should change as a result from some solution, that wouldn't exactly be a catastrophe. –  Christian Nov 16 '12 at 9:20
2  
Ok I understand your question a little better now. There's a simple way to overcome the issue you're having with placement. Instead of doing a copy/paste, select the object or objects (use the shift key to select multiple objects) you need a copy of and duplicate it (Ctrl-D). When you duplicate an object it appears right on top the object being duplicated and voila your alignment issue is taken care :). –  dinesh Nov 16 '12 at 10:31
    
Ah great, I hoped there was such an easy way to solve this! :) I will just accept your existing answer. I hope if someone with the same problem gets here, he or she will also find your comment. –  Christian Nov 16 '12 at 14:31

It seems to me easier, draw three path, and the use tool spinbox labelled grow/shrink to fill them.

So avoid interction tool.

enter image description here

share|improve this answer
1  
could you provide any visuals with your answer? –  Ilan May 1 at 10:14

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.