Inkscape inner shadow

Question

So this is driving me absolutely crazy. I have created this svg of a gear that features a shadow only on the inside. Also it's important to note that this "inner-shadow" is it's own object, and consists of a fill and a stroke that are basically both the outline of the gear shape in black and grey, but somehow when I blur or unblur it t0 0.8% the effect only happens on the inside. I am trying to reproduce the same design, but I cannot remember exactly how I did it and now when I attempt to blur it, it doesn't look the same at all. Using the Filter "Cutout-Glow", I get nearly the same results, but it only works when there is a fill present. As mentioned before on the other examples the fill color is an entirely different object beneath the outline. This imgage shows exactly what I'm trying to recreate:

Any help or insight is greatly appreciated!

Answer 1

I am assuming that your question is:

How do I reproduce the same gear design that is visible in the image?

You can reproduce the effect by applying the "Drop Shadow" effect twice.

You might have done it differently and surely there are several ways to achieve the effect. Here's how I did it, based on what could be observed in the image:

1. Create the base shape (the gear with a gradient) without any stroke.

2. Duplicate the shape. Select the first copy and apply "Filter" > "Shadows and Glows" > "Drop Shadow" with the following settings:

   

   Use a black shadow with high alpha (RGBA 000000c8) in the "Blur color" panel.

We're basically already there (the southeast shadow looks good), but notice how the original also has a slight shadow facing west. Let's create that.

3. Select the second copy and apply "Filter" > "Shadows and Glows" > "Drop Shadow" with the following settings:

   

   Don't forget to choose "Inner cutout" for the shadow type. Again use a black shadow with high alpha (RGBA 000000c8) in the "Blur color" panel.

4. Center the second copy on top of the first. You may use "Align and Distribute" (Shift+Ctrl+A) for this. This should give you the final result:

That's it.

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A remark regarding the "blur problem" that you experienced: After you apply an effect that uses blur (e.g. "Cutout Glow" or "Drop Shadow") to an object, the "Fill and Stroke" panel will show some percentage value for the blur property. I believe this is some sort of average of the different blurs applied to the object as part of the effect (an effect could have a heterogenous mixture of different blurs, that's why it's an effect and not a simple slider).

If you then alter the blur value via the slider, the object's blur will be completely messed up (like you experienced). In other words: Don't touch the blur value after you have applied an effect. If you must control the blur of a stroke outline, duplicate the outline before applying the effect and work with the duplicate. But as you saw, the overall effect can be achieved without using a stroke outline at all.