Blackmagic Forum

Hi,

I've been trying to use a method of masking that I've used for years and all of a sudden I am getting weird issues with the glow tool.



I have an animated scene of neurons with impulses flashing across them. I have a mask pass where all of my 3D objects are rendered black, with the nerve impulse areas rendering as white (See the right side of the attached image.) I take this mask pass and use the image luminescence to generate an alpha to use as the Glow mask. This generally works fine but it fails on random frames. On this frame the whole image gets a weird yellowish tint. (see Glow_not_working image)



Any idea why this is happening? The mask pass seems to be fine on the frames that are failing and the alpha values seem OK. I have tried using both the LumaKeyer tool and the luminance setting on the Bitmap mask tool but I get the same problem with both. I have also tried different filter types on the Glow tool and different import setting on the mask loader, but this didn't help either.

Update: I found that if I change the loader's depth settings on my color pass the issue goes away. For my color pass I have saved the sequence as 32 bit exrs with embedded channels. If I manually change the depth to int16 the issue with the glow masking gets fixed.

Does anyone have an explanation for this?

do you have any negative numbers in the mask render?

Hi Micheal,

Thanks for asking and sorry I forgot to mention that. When I view the mask pass with the color inspector I don't get any weird values. All alpha and RGB values are between 0 and 1.

Update - I still run into this issue. Does anyone have an explanation or a fix for this?

did you try to set the mask to be 8bit or ad a brightnes contrast and clip blacks and whites?

it might be one pixel which you dont getby measuring with your mouse...

Might be NaN values in the blue channel.