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Newly created VSE strips should default to Blend mode = Alpha Over
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Authored by Robert Forsman (mutantbob) on Sep 11 2014, 11:40 PM.

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Summary

The default Blend mode of strips in the VSE appears to be Cross. While there are a great many use cases where this is not a problem, there are a significant number where Alpha Over is a better choice. Add to this that Alpha Over is also appropriate in most of the other cases.

I predict that this change will reduce the number of users who are confused when they try to do overlays using the VSE, and reduce wasted time as users hunt down a solution.

Therefore I think that making Alpha Over the default Blend mode for VSE strips is worthwhile.

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Event Timeline

Robert Forsman (mutantbob) retitled this revision from to Newly created VSE strips should default to Blend mode = Alpha Over.Sep 11 2014, 11:40 PM
Robert Forsman (mutantbob) updated this object.
Robert Forsman (mutantbob) updated this revision to Diff 2578.

I agree with this change - I use VSE regularily and 9/10 of my strips need to be in alpha over mode.

The only other functionality aspect that might make this better would to actually remember the setting of the last strip added. So it could default to 'cross' and then if the strip is changed to 'alpha over' it the next strip added would default to 'alpha over'.

Just my two cents, but why the extra variable (default_VSE_strip_blend_mode), when you could have just replaced SEQ_TYPE_CROSS with SEQ_TYPE_ALPHAOVER ?

If it's for readability, then I'd suggest a name more consistent with the rest of the sequencer API, e.g.: sequencer_strip_default_blend_mode.

I used a variable to be self-documenting. I am not married to the name, and if this patch gets accepted for commit it should be slightly easier for the committer to change the name of the variable than it would be to figure out which instances of SEQ_TYPE_CROSS are blend_mode initializations and needed to be changed.

Campbell Barton (campbellbarton) requested changes to this revision.

Agree SEQ_TYPE_CROSS is quite a strange default, (it can subtract alpha from whats below it).

Would just replace all SEQ_TYPE_ALPHAOVER without bothering with some global int.

This revision now requires changes to proceed.Feb 4 2015, 7:20 PM

@Antony Riakiotakis (psy-fi), could you check with artists on this?

Try make an image with alpha and overlay it on an opaque backdrop, cross gives quite strange behavior (at least different to gimp/photoshop)

I see a small difference with some test images but I can't be entirely sure too...do you have any test files we can share?

For the record I don't mind changing this to alpha over.

also i think that when an user adds an effect strip it should use the same blend mode as the original strip