Guys, PLEASE help :-)

[qalunaq]

Make a shadow/matte material solution for compositing.

I know that the Monte Carlo rayshooting isnt suited for that, BUT, you could make a backplane that stays parallel to the camera, and as the shadowonly shader you could use an alpha based material that gets the shadow samples, but somebody needs to code this, cause it defies the natural material behaviour, you need to make some special shader code i know But please, even without the image plane, we all need it really bad.

Werner

PS: look at my second idea below!

[Refracty]

yip, requested since the early beginnings of Octane.

Very useful.
I hope Abstrax will get his hands on a shadow catcher shader

[vinz]

yes Shadow catching, is more than usefull it's necessary ... for now i'm catching shadows on a white diffuse material that i use as a mask on picture editor! but it's far of perfect ...

I hope something will be done for that ...
as for region rendering ...

[acc24ex]

they should definitely put it on the next release list - since most of the other basic stuff is working, from alpha, sss and instancing, now shadow catcher should be a must, to complete the basics
and sun+hdri

[kavorka]

I agree, a shadow catcher would be very useful in my day to day work.

[nildoe]

+1 shadow catcher

Nildo

[matej]

+1 for shadow catcher

[qalunaq]

Following would be even better for shadows!

imagine a ground plane on which from the camera angle is projected the BG image 1:1, so that the ground plane is textured trough projection and
(best of all) 1. no need for shadow catcher, 2. the ground plane would color-GI the 3D models and 3. (maybe?) the groundplane could be a mesh with additional properties like glossy, etc..

In this case, there would be only a material needed for texture camera projection. Thats all. Can you do this guys ? c'mon
It s way easier than my first post and no special materials needed. Only camera BG projection.

Also the whole compositing is passé! Because the BG image is inside, AND MOST IMPORTANT, it responses to the FILM/ISO/fstop calculations done by octane, which is immensely great !!!

PS: this distorted projection on the ground plane (that looks normal from the camera), gives GI interaction to the scene and looks beautiful because not only the shadows are cast, but the whole light contribution would emerge from the BG image

This is abstract, if you need more info contact me on Skype.

[vinz]

Thanks qalunaq ! i hope it could help someone ...
But this trick don't work with my needs and for the kind of work i'm doing.
imo, i think a lot of people here know these tricks especially people that need shadow casting

vinz

[Refracty]

qalunaq, the idea is good but I would like to see a solution that adds some flexibility for post production. If the resulting shadow is extracted like using a difference key, that would be great.
A shadow catcher material should be easy to implement. If you need reflected shadows on the objects and object reflections on the ground plane without the (HDRI) environment things get a bit more tricky.