Add / Subtract based on brightness?

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Herbert123
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Add / Subtract based on brightness?

Post by Herbert123 » Fri 07 Dec 2018 22:48

I received an architectural 3d render from a client, and it consists of quite a lot of black and white masks that define various areas for selection. Load a mask based on one of these is no problem by using the SHIFT key and clicking on the layer thumbnail (mask based on brightness), but for the life of me I don't remember how to add a second or third based on other layers' brightness.

I seem to recall being able to do that in PhotoLine before, but generally I work with transparency based selections, and those work without any issues when holding down CTRL and SHIFT/ALT. Yet I cannot seem to add a brightness-based mask to an existing mask.

The manual only mentions that holding down ALT loads a mask based on brightness. No mention of how to ADD or SUBTRACT to that same mask using other greyscale layers based on brightness.
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Martin Huber
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Re: Add / Subtract based on brightness?

Post by Martin Huber » Sat 08 Dec 2018 16:51

You can't do that in the Layer List, only in the Channel List. There are just too few modifier keys.

In the Channel List, clicking a thumbnail with Ctrl (Command on macOS) will create a selection based on that channel, Ctrl+Shift will add to the selection and Ctrl+Alt will subtract.

Depending on what you want to do, you could use layer masks. Adding several masks is a subtraction, using a group containing layers with the mix mode "Lighten" as layer mask is a kind of addition.

Martin

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Herbert123
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Re: Add / Subtract based on brightness?

Post by Herbert123 » Wed 12 Dec 2018 01:04

I tried various work-arounds, but so far those prove to be quite clumsy.

Switching to the channel panel will always display ALL the visible layers, so it means first hiding the unneeded layers. But with more complex multi-layered 3d comps it takes way too much time and is very cumbersome. Not to mention quite error-prone.

Of course I tried to work out a quick method to convert masks to layer masks, but that means having to virtual copy masks all over the place, and again takes a lot of effort and time.

In Photoshop I used to just be able to do this quite efficiently, but it is impossible to do in PhotoLine in a convenient way.

It would be simple to solve this by allowing the SHIFT and ALT action to work on multiple selected layers: select the layers you'd like to work with, and hold down SHIFT while clicking a selected layer thumbnail to add to a luminance based mask/lasso based on those selected layers. And holding down ALT and clicking on one of the selected thumbnails will subtract from that mask. That would solve the lack of available modifier keys.

Or perhaps a switch in the channel panel to display only the selected layers.
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Martin Huber
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Re: Add / Subtract based on brightness?

Post by Martin Huber » Wed 12 Dec 2018 12:08

Herbert123 wrote:
Wed 12 Dec 2018 01:04
In Photoshop I used to just be able to do this quite efficiently, but it is impossible to do in PhotoLine in a convenient way.

It would be simple to solve this by allowing the SHIFT and ALT action to work on multiple selected layers: select the layers you'd like to work with, and hold down SHIFT while clicking a selected layer thumbnail to add to a luminance based mask/lasso based on those selected layers. And holding down ALT and clicking on one of the selected thumbnails will subtract from that mask. That would solve the lack of available modifier keys.
I am not a Photoshop expert, but AFAIK this approach differs from Photoshop. And it requires that a simple click on a thumbnail creates a mask based on the intensity of that layer.
Btw. how do you add the intensity of a layer to the mask in Photoshop?

Currently in PhotoLine there are two ways of creating a mask based on a layer:
- using its transparency (Ctrl (Windows)/Command (macOS) + click on a thumbnail in the Layer List)
- using its intensity (Shift+click on a thumbnail in the Layer List)

By user request, we have extended the transparency case: Ctrl+Shift will add to the mask, Ctrl+Alt will subtract (AFAIK this is what Photoshop does).

So it would be possible to add Alt+Shift for subtracting the intensity from the current mask, but Ctrl+Shift is ambiguous: It could be either "Add transparency" or "Add intensity".

Martin

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Herbert123
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Re: Add / Subtract based on brightness?

Post by Herbert123 » Thu 13 Dec 2018 03:55

I do like the current behaviour in PhotoLine: shift/alt to add or subtract from the transparency mask. It works fine.

What about if it is checked which modifier key is pressed first? Ctrl-->shift add to transparency mask, Shift-->Ctrl add to luminance mask.

Or would that be difficult to check for?
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Re: Add / Subtract based on brightness?

Post by Martin Huber » Thu 13 Dec 2018 11:52

Herbert123 wrote:
Thu 13 Dec 2018 03:55
What about if it is checked which modifier key is pressed first? Ctrl-->shift add to transparency mask, Shift-->Ctrl add to luminance mask.

Or would that be difficult to check for?
I'm not sure this is a good user experience. On the other hand, you don't really lose anything.
I'll check that.

Martin