Thank you for the patch Cyrille. It's a very nice solution.
The only disadvantage is that it makes the background image feedback dependent.
My goal is to isolate the feedback from other geos & image/videos.
So, I was thinking that in order to keep the blur I have to keep the gemframebuffer RGB format and add transparency after it.
I just realized that [alpha] has several blending functions, some of them turn the whole framebuffer transparent.
This is fine but now the geo and blur are also affected (see attached).
I don't know if it is possible to add other type of blending after the framebuffer, maybe sending it to another gemframebuffer and changing the background color (black) to alpha?
I saw that pix_alpha achieve this but I don't know how to use it only with the framebuffer image. Any suggestion is welcomed :)

regards,
andre



On 27 August 2017 at 11:48, cyrille henry <ch@chnry.net> wrote:
hello

Le 27/08/2017 à 03:05, andre rc a écrit :
Hello,

I'm trying to apply motion blur only to one geo with gemframebuffer.
It works fine until I add a background image: when I switch the gemframebuffer format from RGB to RGBA the amount of motion blur decrease considerably.
yes, since the feedback image became more and more transparent...



Is there a way to get the same amount of motion blur (long tail) with alpha on?
replace [color 1 1 1 0.95] with [color 0.95 0.95 0.95 1]

but that's not what you want since it will fade to black and not to transparent.


an other solution would be : you can alter the color of the feedback image by drawing a bit of the BG on top of it.

attachment example.

cheers
c

Attached example.

thanks & regards,
andre



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