Transparent material not behaving correctly with alpha

[TeoRossi93]

Hey guys!

I’m trying to render a glass object on a transparent background. Unluckily I’m not able to keep reflections visible in the alpha.
Any ideas on how to keep them visible without rendering a reflection pass and composite it in after/photoshop?

[Mvskokvl]

“Eeryone coins its own luck.”
So what’s your setup, sys-specs…?

i.e.
Simple setup (W10, R23.110, CRN 7daily) saved as .exr, (16bit) composited in GIMP

Glass-TransAlp-ha.c4d (178 KB)

[TeoRossi93]

I run c4d r22 and corona 6 for this one (i even run c4d 23 and corona 7 but I just use it for test purpose).
The problem is that I have to composite an animation, no problem to make this work in still images.
Anyway your render looks pretty different from the image opened in gimp.

[Mvskokvl]

@TeoRossi93

…your render looks pretty different from the image opened in gimp.

Yup.
And now, something completely different…

Basically:

Straight vs Premultiplied : Understanding Alpha Channels

Have fun.

[ficdogg]

I’ve had to do something similar and I ended up just setting up render passes for reflection and refraction in addition to alpha, and then comped everything in After Effects. You can see the end result here.

MAGFAST Air - Reimagine Wireless Charging

This was rendered on gray, the blue color and DOF were added in post.