Author Topic: Brush Blend Modes  (Read 643 times)

GlennNorfolk

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Brush Blend Modes
on: May 09, 2019, 06:35:22 AM
Brush Blend Modes...

With every Art App I've ever known, I've never understood why Brush Blend Modes do not operate on content beneath in the same way as Layer Blend Modes - i.e. on content but not on blank areas?

Brush blend modes, as we all know, operate as shown below.



I cannot think of a single scenario where this makes sense. I find I am ever switching back and forth between one layer with normal mode and another (even more than one) with the mode I want to use, to change the colour or whatever of my existing, underlying mark.

I've asked about this in other Art forums but have never had a rational explanation - and yet no-one has pointed out what it is I'm not getting (as it seems I must be missing something)...

I wonder if you - or someone here - might be able to help me understand...?

~~~~~

[[I can't see how to load an inline image into the Image Tags ]]

Lucky Clan

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Re: Brush Blend Modes
Reply #1 on: May 09, 2019, 05:08:19 PM
It is simple :)
Let's say you are using Hue blend mode.
When you paint, the stroke is affecting only the active layer, all other layers are ignored.
To achieve the same effect with layer blending you have to disable white background layer (so Hue layer is blended only with the layer below).

How layer blending works: let's say you have 3 layers. First, the bottom (background) layer is blended with layer 1, then the result of that is blended with layer 2.

If you enable background layer (white opaque), the top layer (the one with Hue blending mode) will affect all layer below (not only the one below). To achieve the same effect with brush blending you have to first merge Background Layer and Layer 1, and paint on the merged layer (which is opaque).
Last Edit: May 09, 2019, 05:10:30 PM by Lucky Clan

GlennNorfolk

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Re: Brush Blend Modes
Reply #2 on: May 10, 2019, 12:02:33 PM
Thanks for reply, Lucky (Do we call you Lucky - never really known)..?

No, I fully understand all about Layer Blend Modes - I was only mentioning them to illustrate my point about Brush Blend Modes behaving unsatisfactorily compared to them when strokes of non-Normal brush mode are applied to blank areas.

Referring to my 2nd image... (particularly the transparent background).... First the reds are painted using Normal Mode. Then (same layer) blue is painted, using the 3  (HSL) modes.
Over the Reds: perfect. That is just as we'd expect: the red being changed according to whichever mode the blue is using.

But... and this is my point.... why should those three modes (HSL in this example) act at all on areas of the layer that are blank (in this case, non-red-painted)??
If blank, then there is nothing for the (e.g) Hue Mode to change the Hue of..! Instead, on any blank area, the Active Mode is ignored and the stroke is painted as if in Normal mode!
I've never understood how that could possibly be considered desirable!

My thinking would be: (using Hue Mode, or any other non-normal)...as the brush paints:   if content present, change its Hue; if nothing, do nothing...

(Of course, as I said before, I know this is a universal thing, so not directing this at ASPro..! :)  Just wondered if you could point out what advantage there might be in how it currently works)..?

Last Edit: May 10, 2019, 12:12:04 PM by GlennNorfolk

Lucky Clan

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Re: Brush Blend Modes
Reply #3 on: May 11, 2019, 06:42:48 AM
Blending modes work in a similar way in most similar apps, users expect that in other apps as well.

If want to keep blank areas unchanged - just use Clipping Mask.
What you are asking is auto-enabling clipping mask for non-normal blending modes, it would be counter-intuitive.

GlennNorfolk

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Re: Brush Blend Modes
Reply #4 on: May 17, 2019, 03:48:20 AM
Yes, I do use Clipping Masks (and other workarounds) to protect blank areas when using Brush Blend modes.

My point is: why should we need to??

Whenever I ask why Brush Blend Modes work this way, the answer seems always to be "we do it this way because everybody else does it this way"...

No-one says we do it because it is the right way - the most useful, most logical way...

If someone can show me one example, one scenario, that wants a non-Normal Blend Mode to paint in Normal Mode on blank areas, then I will understand.

(( Apologies if I'm being a bore on this.  As I say, not directed at ASPro - just it's something that's always completely baffled me whichever App I use...! ))
Last Edit: May 17, 2019, 04:00:18 AM by GlennNorfolk

Lucky Clan

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Re: Brush Blend Modes
Reply #5 on: May 22, 2019, 06:39:57 AM
I agree with you, it is very hard to find a scenario when it is useful :)