Vray Matte Problem with Shadows

[raistlin]

Hi everybody

I've got a problem with matte option and shadows
I've a scene to render with some objects and i want to separate them by passes, so i've isolated some of them and make pass like that
(sorry for the worst render but this is a test scene without shaders and others... Just the necessary)
The Fix Object pass

And his alpha


The animated objects

and they alphas


For the test i have a imple solid I do into AftFx as background

And the result is here :


As you can see the problem is on the animated objects... The first spanner cast a shadow as nothing is beetween it and the light, but the furthest is casting shadow on the right way...
I've trying a lot of combination, and the only solution i've found is to render all the pass without shadows and render the shadow pass in one time..; But... It's really a non-sense... If i have to render with passes i'd like to do it separatly... and not to rendering All the sequences just for shadows...
Please help me to found a solution... I'm going crazy...


Many thanks !
Many thanks !

[raistlin]

Nobody knows?

[raistlin]

Damned it's a real unknow issue? how could we work with that???

[Morne]

that does look strange
but its such a small scene, why dont you just render the pipe and animated object in 1 go?

[raistlin]

Lol... I finish by render in one shot of course (the dead line was passed for 4 days now) but i want to know how could it work well in other case? (I have a great projetc to do in HD with a tons of vegetation and others animated object...)
So i can't understand how to avoid this problem... I can try to create a small scene this night and share here with you... But i really cannot understand...
So, thanks for your answer, you are the only one who answer me in near a week...

[Morbid Angel]

when you deal with splitting out the shadows, you are actually dealing with a lot more complex operations then you would think. You need to understand what is happening with the shadow in your scene before you can properly split it out. There is two types of shadows that are happening here, the direct and indirect shadow. One is contributing to the luminance of the other. In order to composite properly these elements, first you must out put a pure direct shadow alpha, where the shadow is a pure white value of both elements. Then you must do the same for the pure indirect shadow as a separate element. Separate for each element, so you will have 4 shadow elements in total. Once you have the pure white alpha of the direct shadow you would add the two together merging them into one solid shadow alpha, then you would add the two indirect shadow elements making them into one solid element. After that you would multiply both elements over your bg, with control as to how much each is contributing.

[raistlin]

Mmm ok i've understand my mistake, i'was focused on the result and not on "how i can do the shadow correctly", my mistake was i'm trying to do layers like in photoshop... But, i've to composed some passes together before to have good result...
But how can i do the thing? The indirect shadows are done with Gi (if i have understand) and the direct was done with the lightnings directly. So i've to use some render elements to do the trick?