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beyond-all-reason / spring

A powerful free cross-platform RTS game engine
https://beyond-all-reason.github.io/spring/
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LuaOpenGL::Text ignores color alpha when drawing outline #906

Open salinecitrine opened 1 year ago

salinecitrine commented 1 year ago

For very low alpha values, the result is drawing basically just the outline, which looks awkward.

alpha = 0.1: outlinealpha

alpha = 0.02: outlinealpha2

I encountered this while developing https://gist.github.com/salinecitrine/7f6e21ed304eeaba9ad4a122019c0d82 . I ended up using a workaround where I draw extra black copies of the text, offset by a few pixels.

alpha = 0.1, with my workaround (indicating very approximately what I think it should look like instead): outlinealpha3

lhog commented 1 year ago

Firstly, try to avoid gl.Text() as its interfaces is somewhat more limited than dedicated Lua font API https://springrts.com/wiki/Lua_Fonts Secondly, can you provide the exact snippet which didn't work as expected for you? The gist you linked doesn't seem to use engine outlines at all.

salinecitrine commented 1 year ago

Firstly, try to avoid gl.Text() as its interfaces is somewhat more limited than dedicated Lua font API https://springrts.com/wiki/Lua_Fonts Secondly, can you provide the exact snippet which didn't work as expected for you? The gist you linked doesn't seem to use engine outlines at all.

I had assumed that gl.Text(...) in widgets referred to this function; does it actually point to a different one?

There isn't a direct example in the gist, since I replaced it with a workaround, but something like this is what I had before (with "o" added for outline here compared to the gist):

glText(text, 0, 0, currentFontSize, "cdo")

Thanks for the tip on Lua Fonts, I'll try that out instead.

lhog commented 1 year ago

Automatic outline has fixed outline colors: 0.95f, 0.95f, 0.95f, 0.8f for light outline and 0.15f, 0.15f, 0.15f, 0.8f for dark outline

As far as I can tell we have no alpha testing enabled or anything similar during the font rendering so any reasonable alpha should get in. 0.02f / 2% is pretty low though and it might be easy to miss. Just to be 100% sure in the statement above I additionally disabled alpha testing, though it should have had no effect with a shader in place anyway. https://github.com/beyond-all-reason/spring/commit/2f128c398cccde38b7c9b6ebe003b9cdc28d1000

sprunk commented 1 year ago

I think the request here is to keep the outline alpha relative to the main text, so something like:

lhog commented 1 year ago

I'm thinking to extend the inline color marking to include outline/shadow color and alpha channel. https://github.com/beyond-all-reason/spring/issues/884

Automatic color of the outline is currently defined by option o or O to do light or dark outlines, they use a fixed alpha value. I'm happy to change that if someone can come up with a sane formula of how to derive the outline's alpha, from the main color or main's alpha.

salinecitrine commented 1 year ago

I'm thinking to extend the inline color marking to include outline/shadow color and alpha channel. #884

Automatic color of the outline is currently defined by option o or O to do light or dark outlines, they use a fixed alpha value. I'm happy to change that if someone can come up with a sane formula of how to derive the outline's alpha, from the main color or main's alpha.

Just my opinion, but from my own work on the widget I linked, I found that outlineAlpha = 0.7 * mainAlpha was simple and looked good to me.

I only tested with red and green, so perception might vary for other colors. I also tested out subtracting a small amount (~.05) from the outline alpha so that you never had a case where the outline was more visible than the main text (I ultimately removed it; the discontinuity when fading was hard to make look ok). outlineAlpha = 0.7 * mainAlpha * mainAlpha might work better for the same effect.

sprunk commented 1 year ago

Current:

This draws the inside of the letter twice, so at any values of <1 text alpha and >0 outline alpha it will be polluted by the outline color even on the inside of the letter.

How about this?