Disabling "Cast Shadows"... casts shadows?

[Alex_M]

I just found a weird behavior. If I disable the "Cast Shadows" property of an objects that has an opacity map, that whole object starts casting a shadow, even the parts that have full transparency. If I disable "Cast Shadows", the object still cast shadows, but only the opaque parts as it should. Screenshots below.

[hermit.crab]

The shadows are disabled as expected on a simple scene (tested with V-Ray 5, update 1). Could you strip down yours and send it (or attach it here) via the contact form so we can take a look. Address it to me in the subject and mention this topic in the message.

[fixeighted]

My guess is that it is not shadow but reflection....

Indeed, if the surface below the opacity mapped plane has blurry reflection then the whole plane is visible.
It's fine if you disable it from reflections but in a circumstance like the attached it's far from ideal

Can't think of a fix for that atm but it solves your issue for the logo I guess.


EDIT: Happens when lit with a dome or other vray type light. Vray sun works as expected.

[Alex_M]

It was indeed a reflection. Thanks, fixeighted! I disabled reflections for the object and it is no longer creating a dark spot below.

Should I still send the scene, aleksandar.hadzhiev?

[fixeighted]

This totally threw me and although I am very pleased to get a fix for your thing, it threw up the obvious issue that it still happens if you e.g. wanted a reflection, for a particle system, or whatever, with opacity mapped planes.
So, for reference...and for me too, as I can search my posts when I forget .....you need to not use opacity, rather use refraction, for it to work universally

[vlado]

This is odd indeed and looks like a bug... looking into it. There is no need for a scene, I can reproduce this here.

Best regards,
Vlado

[fixeighted]

If it makes any difference, it's the same with Next (maybe older too) as with 5.1

[timmatron]

Hi,

I just found this. The bug still seems to be there. I would never have guessed that turning on "cast shadows" would solve the problem. I almost always have "cast shadows" turned off with labels like this, which is why I couldn't understand why it was casting a shadow over the whole thing unless I turned off "visible to reflections". But I'm glad I saw this, saved me from posting a new thread!