The smear brush on sculpt mode is causing vertex color alpha to keep increasing (see `before` video). I think the amount of alpha should decrease the further away it gets.
My solution is to remove the blending of `accum` with `interp_color` and eliminate the usage of `interp_color` altogether. This will correct the behavior, as seen in the `after` video below.
I provided a [blend file ](/attachments/470b7c27-5707-4d8a-83ea-28a7423f7092) for you to test.
| Before | After |
| -------- | -------- |
|<video src="/attachments/8f28899e-13f2-455f-ac42-dd1464330f3a" title="demo_before.mp4" controls></video>|<video src="/attachments/041389b7-350e-44e2-84cb-a41f26905880" title="demo_after.mp4" controls></video>|
Co-authored-by: Ahmad Rifai <riff.blend@gmail.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/115292
71261f5212