Questions About Smudge Colour VS. Smudge Length and Eliptical Dab Angle VS Ratio

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#1

Hi everyone,

Per the title, I am wondering what the exact difference is between smudge colour and smudge length, as the description in the tool tip is slightly unclear. What exactly is the “smudge colour” by definition? How does this relate to the canvas? The SC tool tip states that you can paint with the SC instead of the brush colour, and the SC is slowly changed to the colour you are painting on. Seems straightforward enough, but the smudge length tool tip states that the SC is slowly changed to the canvas colour. Is that the white base canvas (or whatever other background can be set, like paper texture, ect.)?

Further, my questions about Dab Angle came about as I am trying to create a semi realistic flat bristle brush as might be found in Photoshop or Krita. As I’ve heard before, this particular task is difficult in MyPaint, but I’d still like to give it a try. In my experiments setting a basic brush to have a single dab (approx 0.2 per actual radius) adjusting the Dab Ratio appears to make the stroke fly off the canvas. Why? I’m hoping a better understanding of what these settings are designed to accomplish individually will make brush design easier.

Thanks!


#2

I guess I would call it a 3rd color that may be different from both the brush color and the canvas color.

The Smudge Color accumulates the canvas color by sampling it periodically and combining the sampled color with the existing Smudge Color.

Smudge Length affects the sampling interval. At 1.0 it will never sample the canvas and freeze the Smudge Color at whatever it was before. At 0.0 it will sample very frequently. This is relative to how many dabs are being drawn, too. The sample is taken from the current Layer, which starts out transparent even if you have a white or texture background (the background is not part of any layer). So, the Smudge Color by default will be pure transparency (RGBA 0,0,0,0).

We’ve managed to make some pretty spiffy flat brushes using @AnTi’s dab offsets. I have some in my brushpack. I also made a tutorial on youtube that might help.

That shouldn’t happen (maybe you can update MyPaint if this is a bug). The dab ratio is just how round or oval the dab is. 1 implies a 1:1 ratio, which is round. wheras 9 is a 1:9 ratio, very squished. Once your dab is not-round, you can see the effect of dab angle, which changes the orientation/rotation of the dab.

That said, in my experience you get better performance if you keep the dab ratio 1 (round) and not worry about angle. For a realistic brush I think it is more important to have a lot of small dabs whose appearance doesn’t matter so much. After all, real brushes are made of tiny hairs, not large bitmaps and stamps.

Turn on the Live Update feature in the brush editor and start experimenting :slight_smile:


#3

Thanks very much for the help! It appears my main misconception was to do with the “canvas” as it applies to traditional art. I did some tests, changing the background from white to black and a variety of other colours in the Background Chooser, and then painted with 2 colours on the palette. The 2 colours mixed without noticeable interference from the Background Chooser colour. I originally assumed due to the wording of the tool tip that the sampling when smudging would reach through the transparent drawing layer and leech from the background, mixing that with whatever 2 colours you were mixing.

I’ll conduct some more experiments with the brush editor and see what I can come up with. I am not sure yet if the dab issue was just a glitch or not.

Cheers!


#4

I think you could consider the background to be a primed dry canvas. So, it never mixes with your brush paint and that makes sense. So you literally need to use the paint bucket tool to put a layer of “wet” paint on the canvas if you want to have a wet on wet type of blending. :slight_smile: