vfb foreground image with alpha... not working?

[super gnu]

ive tried as png, tiff, tga, manually saved transparency into a channel called "alpha" whatever i do i get no transparency in the image, it covers the whole render.

[hermit.crab]

I'll investigate and write back. Meanwhile, try using an EXR and see if that makes any difference.

[super gnu]

ok in the end i got it to work.. it has to be a channel called "alpha" a png or tiff with transparency doesnt work. i finally got it working by removing image transparency, creating a channel called "Alpha" with the mask for transparency in, andf saving as a tiff.. this worked but came in with the wrong gamma... i had to set gamma to 0.4545 in ps before saving for it to work correctly.

[rasmus]

hermit.crab

This is still not working for me in max 2024 + Vray 6.20.02. Which combinations are actuaally recommended/supported ( PNG/TIF/PSD (with/without "Alpha") Channel and/or transparency only (-> no "Alpha" Channel)... if Alpha Channel is required, what's it suppsoed to be named?

[hermit.crab]

When using the Background layer with As Foreground active, the VFB uses the color of the i.e .png and its alpha to blend with the render. The formula is the following: Result color = .png_color + (1 - .png_alpha) * Image color. This means that in places where the image's alpha is 0, the blending is the .png color + Image_color (which is clamped in the VFB). Basically, to get what you wish, the .png background should be so to speak black or unpremultiplied. A simple workaround, I've found is to load the image in a 3ds Max native bitmap node, turn off "Premultiply alpha", Render Map, and reload in VFB.