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When scaling down image, users expect to see background, which doesn't currently happen in VSE. This is because strips use cross blend mode by default, because alpha over is much slower. Reason is, because any area of image can be transparent, and therefore it can't have early out implemented in a way that cross blend mode can. Flag images rendered by codecs that don't support transparency as fully opaque and implement a form of early out for alpha over blend mode. When rendering image stack, 2-input effects are ignored on the "way down". Alpha over needs rendered overlay image to decide whether it will use only overlay or background too. Therefore overlay can be rendered safely before it is used. Image flags can be checked and it can be freed if needed. Freeing doesn't cause any performance degradation, because image is always stored in cache. This feature does not improve blend mode performance. In summary, it only allowes for having alpha over blend mode on background images without suffering from lower performance. Reviewed By: sergey Differential Revision: https://developer.blender.org/D12914
.. Keep this document short & concise, linking to external resources instead of including content in-line. See 'release/text/readme.html' for the end user read-me. Blender ======= Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline-modeling, rigging, animation, simulation, rendering, compositing, motion tracking and video editing. .. figure:: https://code.blender.org/wp-content/uploads/2018/12/springrg.jpg :scale: 50 % :align: center Project Pages ------------- - `Main Website <http://www.blender.org>`__ - `Reference Manual <https://docs.blender.org/manual/en/latest/index.html>`__ - `User Community <https://www.blender.org/community/>`__ Development ----------- - `Build Instructions <https://wiki.blender.org/wiki/Building_Blender>`__ - `Code Review & Bug Tracker <https://developer.blender.org>`__ - `Developer Forum <https://devtalk.blender.org>`__ - `Developer Documentation <https://wiki.blender.org>`__ License ------- Blender as a whole is licensed under the GNU General Public License, Version 3. Individual files may have a different, but compatible license. See `blender.org/about/license <https://www.blender.org/about/license>`__ for details.