Good way to composite Hdri and plates

[3LP]

Hi everyone,

I'm here with a tiny question.
I would like to know the good way to composite some HDRI with plates using matte-shadows.

Here are two images of the scene by HDRI-locations.com to explain my point of view.


First one is with a camera map of the plate.
Second one is with the plane as matte-shadow.

We can see that the reflection isn't right.
I could imagine that in the most of the cases, it wouldn't be a problem, but I would like to know how to do it right.

If I put the ground plane as self-illumination, the reflection in the ball would be color-right, but wouldn't have any shadows. Like this example :



To be clear, I only have a problem with the shadows in the reflection with the right color plate.

How do I have to setup my ground to have the right color and the right shadows in the reflections?

[instinct]

Can be done with a Light/Shadow falloff map to tone down the plane. where shadow hits (mask with falloff as mask).

You forgot the copyright notice for Thomas' free HDRI/Plate offer...(in case you didnt buy it that is, so sorry if you did heh)

Regards,
Thorsten

[3LP]

Completely right about the copyright, completely forgotten due to the concentration to explain my thoughts.

Could you do a little example so that I could understand right your way to do ?
thanks a lot.

Stan
3LP Team

[Morbid Angel]

the reflection wont be right...you need to make the plane not visible to reflections. Also you need to make your reflection environment (I assume its a dome light - full spherical dome.) This way the only thing visible will be the ground below.

[3LP]

@ instinct :
Thanks for the tip, I will try that out, but is this the good way to do it ?
Is it the way we have to do it in production?

@ : Morbid Angel :
I'm very surprised that you say that there isn't any possibility to do it right.
Because HDRI is good, but with a floor for example, the HDRI wouldn't far not be enough to have a accurate reflection in the objects.

Is there any other possibility ?
Isn't there in Vray a option/may where that could be setup to have thoses things right ?
Does all the peoples that use Vray in production have always there reflection wrong? Or does they find that this mismatch is "acceptable"?

Thank you for your tips anyway, but I would know if there is a beter way to do it, to be accurate.

Stan
3LP Team

[instinct]

Well a camera mapped HDRI for sure will be worse then the original HDR. So you need to rebuild the environment if the HDRI isnt good enough.

Regards,
Thorsten

[sv]

do a multi-pass render - one for the reflections, then separate shadow passes and comp them in. Split the shadow into GI shadows and direct shadows also...