How to increase mouse size by velocity?

[marigolden]

I want to vary my line thickness as I paint to match a style of an image, but can't seem to find how to input this setting I'm reading about, varying the mouse size with how fast you move it. I'm sure one of you GIMP wizards must know TIA

[denzjos]

Use one of this :

   

[Ofnuts]

Technically what you want would be done with one of the "Brush dynamics" that links the brush size to the "velocity" of the pointer.

However, if you are using a mouse, this won't work well, because the pointer movements on the screen are not a linear map of the mouse movements on the mouse pad. If the mouse moves faster, the pointer will move even faster, this is called "mouse ballistics"(*). Try this:

• put two heavy things (books) on your mouse pad with about a hand's width between them
  
• tuck the mouse against one, and move it slowly until it is against the other. See how much distance your pointer has move the screen
  
• do the same but jerk the mouse quickly. The pointer will have moved a much longer distance (it is likely against the screen).
  
• you can also try to sign your name with the mouse... see how hard it is?
  

In other words, these options are really meant to be used with a tablet, which is designed to map "linearly" the pointer moves to the stylus moves.

(*) This why mouse pads should be used in "portrait" mode, because you can move your mouse laterally a lot faster than "vertically": you need less horizontal room, and your portrait-mode mouse pad maps to a landscape mode display.