Caustics shadows changing?

[DAVIS_PARTNERSHIP_DM]

I haven't had this issue before but now that Im in Vray 6 when applying caustics it changes the shadow angle considerably within the water. What am I missing here?

Ive adjusted IOR just to see if something funky was going on there and it made no difference to the shadow line weather I set it to 5 or 1.

Same results if I switch from Progressive (WIP) to Photon Mapping

Single light source - Sun

Photon Emit Radius is covering the entire scene.

[vladimir_krastev]

Hi thanks for posting. It looks as if you've moved the sun in the second image. Do you have issues only in this scene or in a new scene as well? Could you send us the scene? Please share it here or trough our support contact form.

[^Lele^]

I haven't had this issue before but now that Im in Vray 6 when applying caustics it changes the shadow angle considerably within the water. What am I missing here?

Ive adjusted IOR just to see if something funky was going on there and it made no difference to the shadow line weather I set it to 5 or 1.

Same results if I switch from Progressive (WIP) to Photon Mapping

Single light source - Sun

Photon Emit Radius is covering the entire scene.

This is the normal behaviour (see the tooltip on the "affect shadows" checkbox).
Assume the calculations done with "affect shadow" off to be accurate, when coupled with caustics.
The default method is not physically accurate, and works fine when caustics aren't calculated separately.


"Affect Shadows" ON, no caustics calculated


Affect Shadows OFF, before caustics are calculated
Affect Shadows OFF, caustics completed (notice this now looks a lot closer to the original, but with much more nuanced shadow intensities, thanks to caustics.)

[DAVIS_PARTNERSHIP_DM]

Thanks, I have it setup like you show. Is there no way to adjust settings to make the shadow shift due to the caustics less altered during the calculation? Ive linked video showing the change I'm getting in affect.
https://drive.google.com/file/d/1M0u...ew?usp=sharing

[^Lele^]

I'd assume the bump is the responsible party here (after all, it's a trick.).
Try removing bump entirely, see if it gets any better.
If it does, maybe displacing the water surface will fix the shifting for good.

[DAVIS_PARTNERSHIP_DM]

Oh my gosh! Ok. I figured it out.
So I had moved the sun close to the target so I could do quick adjustments in my viewport and that was causing the issue with the caustics.
Having the sun close to the target like this works fine in all other instances but with caustics on it gets confused.
When I moved the sun farther from the target about 30 ft in the same line it renders caustics just fine.

I had opened an old scene and it was working great in vray 6 and I was so confused and then noticed the sun distance!

[^Lele^]

I'm not sure i see the difference, but i am glad you found a way to have it behave as you expect!

[DAVIS_PARTNERSHIP_DM]

It was all about the shadows in the pool. It was doing something weird and clipping the corner of the pool. I highlighted the shadow with yellow. But yeah working like i want it to now. Thanks for looking into this.

[vladimir_krastev]

Hi indeed it is strange. Thanks for the scene. Here is what I was able to come up with

There is no photon emission behind the V-Ray Sun.
I will check if this has room for improvement and get back to the thread.

[DAVIS_PARTNERSHIP_DM]

Yeah thats what I stumbled upon. Not a bit deal normally but yeah very tricky.

[vladimir_krastev]

Hi, after discussing the matter with our developers I would like to inform you that for now this behaviour will stay. The objects that we want to generate caustics have to be within the limits of the green cylinder which marks our photon emission volume.