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I have the following image created in Gimp.

enter image description here

I'd like to create a similar image in Inkscape. What I want to happen is to have a bright light source and I want this light source to brighten the circles having the most intense effect at the edge of the blue circle.

In Gimp I'm able to achieve this by having a white to black gradient as separate layer on top and setting the blend mode of that layer to addition (using the technique in this tutorial: http://gimp-tutorials.net/gimp-glow-effect)

How can I achieve a similar effect in Inkscape?

  • Is there some reason you can't use gradients in Inkscape? – Scott Sep 9 '15 at 7:56
  • @Scott: No, but how do you get the gradient to go across all three objects? And how do you get the gradient to merely lighten the objects rather than change their color? I have no idea, hence my question – User Sep 9 '15 at 8:00
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    Can' you instead of adding a "layer" just add another object with a white to transparent gradient on top of your circles? – Takkat Sep 9 '15 at 9:38
  • @Takkat: possibly but the resulting image needs to be exported to a transparent png. It seems like with a white to transparent gradient on top, that the white that goes over the background would show through which would not be what I want. If there's a way to do what you suggest but only over the surface of the objects then that sounds like it could work. Also I just mentioned gradient because that's how I did it in Gimp. Maybe in Inkscape a gradient isn't even the right tool. Maybe there is some other technique to have a light source. – User Sep 9 '15 at 10:09
  • @Takkat: thanks your suggestion was enough for me to get the job done. In my case I duplicated the object on another layer and added the white-to-transparent gradient on that object. Although I'd still be interested in an alternative solution in the case where the objects are greater in number and/or more complex. – User Sep 9 '15 at 11:35
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To reproduce the effect you made in Gimp with Inkscape I took the following steps:

  1. Create filled circles and make them a group

    enter image description here

  2. Create a large circle with the gradient circular fill (here black for illustration)

    enter image description here

  3. Duplicate the group of colored circles to then create a unified path (Path > Union)

    enter image description here

  4. Select this new path and the gradient circle to cut out the path intersection (Path > Intersection)

    At this point I added a canvas and changed the gradient fill from black to white.

  5. Move the gradient until happy

    enter image description here

After grouping the gradient object and the coloured circle group we will finally have a new object resembling your Gimp original:

enter image description here


Side note: for more fancy or realistic effects we may also want to try out some of the inbuilt filters to get many interesting effects (below I applied Filters > Bevels > Deep color plastic)

enter image description here

  • I'm curious how do you feel having the separate circle with a gradient (as you have done in this answer) compares to just adding a gradient fill to the unified path object? – User Sep 12 '15 at 6:43
  • @User: yeah it would be the same. The gradient can freely be chosen on the path intersection object (which does not need to come from a circle but could also be any other object). It was done here merely for illustrating the basic principle behind this. – Takkat Sep 12 '15 at 7:21

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