Making an Illustrator scatter brush that changes the size depending on stroke width?

Question

I'm trying to create a custom scatter (or art?) brush which creates a dotted line, but the size of the dots vary depending on the width of the stroke. Is this possible?

Basically, I'm trying to create the effect below. The first line is a simple line with a dot scatter brush applied; the second line was created by expanding the first line, then using the blend tool to blend circles of different sizes.

This is fine for one line or two, but I'm trying to apply this effect to a whole set of lines, so that if I change the stroke width (ie, add a stroke profile), the sizes of the dots will change too:

I'd appreciate any suggestions on how to do this another way!

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Note in response to @GerardFalla's solution: The options next to "size" in the Stroke dialog box are greyed out for me. (Possibly important: I don't use a tablet.)

Answer 1

I saw your question in passing and love a challenge. I think this is as close as you're going to get without a graphics tablet...

...hope you enjoy it anyway...

1. Draw a dot
2. Make it a graphic symbol
3. Make a (straight) line of dot symbols as long as you need
4. highlight line of symbols and create new art brush, name it (I'll called it 'dot line 1'), set option to scale proportionately (this will cut down on distortion)- Do not delete your symbol line!
5. Draw your artwork line and stroke it with your new dot line. You should now have an even size dotted line on your art line (see top of pic).
6. Now the magic starts! - Copy your original line of symbols, you may need to come back to them - and highlight them, go across to the Tool Bar and find the Symbol Sizer Tool (under the Symbol Sprayer drop down).
7. Double click on the Symbol Sizer Tool Icon to open the options menu, adjust the size and intensity of the brush to suit your artwork - I used a big brush and low intensity setting - you may need to experiment.
8. Now click and drag the Symbol Sizer Brush over the active symbols and watch them interactively grow! Then Option Click Drag to watch them reduce!!
9. Highlight the row of symbols, open the Brush menu and Option drag them over your existing brush ('Dot Brush 1') until the preview outline goes thick, When you release the mouse the options box will reappear. Click OK and then click Apply to Strokes when the box pops up and your existing line will be stroked with your revised brush.
10. As you now have a brush which you can change or update it's easy to create blends or copies and just apply one of your dot brushes to the stroke.

Answer 2

Yup - no problem.

Double click on the scatter brush in the brushes in this document pane, and where you initially see "Fixed" (or Random) in the control pulldown for Size, Spacing, Scatter, and Rotation, note you can pulldown to input Fixed, Random, Pressure, Stylus Wheel, Tilt, Bearing and Rotation.

Here you see two versions of the basic circle scatter brush with slightly different settings, used with a graphics tablet to get decent pressure input, and as you can see, with a very little effort I can get both your desired output and a range of other effects quite quickly.

Hope this helps.