shadows overlapping in passes

[chow choppe]

hi everyone

 

i just tried rendering animation in passes

one for still objects and 1 for moving objects

everything has come out fine except for 2 things which i will mention later. First i would like to tell u the process for the 2 passes

 

1.) Still objects pAss:moving cars were unchecked visible to camera, cast shadows was off in object properties. In vray properties of moving objects, generate Gi , receive GI and visible to GI was off. so this way i cud see the cars in reflections of still objects.

2.) Moving Objects Pass: In this i made cras visible to camera and cast shadows turned on, Gi generate and receive and Visible to GI turned on and everyhting else(still objects) were converted to matte, alpha contribution -1.0, shadows and affect alpha turned on.

 

now i when i put these together the problems i am facing are first when i use the alpha suring compositing i see an edge around the moving objects which is similar to the background color i used in moving objects pass.(that problem was solved slightly if while compositing i choose the matte color as the background color but then shadow color changes because of that). secondly wherever the shadow of moving car is crossing the shadow of still objects its overlapping it instead of merging with it. please see the following image to see the problem and help me find a solution for this please

 

 

thanks

[dpcaltdcah]

I am pretty sure it's a bug...

http://www.cgarchitect.com/vb/24462-matte-objects-vray.html

I seriously spent like three days trying to solve this same problem more than a year ago and have been unable to. I think if I remember correctly I even contacted chaosgroup and they couldn't solve it, they blame it on autodesk, autodesk blames it on vray, you know the drill. but good luck...

[kippu]

i dont think is a bug ...it is simple and i am sure he will work it out in no time

[William Alexander]

Looks like glowing edges around the shadows pass. Typically a premultiplication issue during post.

 

Don't see any white glowing edges in the alpha moving pass. Short of restructuring and rendering your passes maybe you can use a dialate-erode (shrink-Grow) effect on the alpha, assuming you're using it as a mask. This can shrink the mask and cover-mask the light colors

at the edges of the shadow in the moving objects pass. Another option might be to change the background color to black in the moving objects pass.

 

What are you using to composite?

[dpcaltdcah]

try rendering your car against a black background instead of blue to get rid of the edge...

[chow choppe]

Looks like glowing edges around the shadows pass. Typically a premultiplication issue during post.

 

Don't see any white glowing edges in the alpha moving pass. Short of restructuring and rendering your passes maybe you can use a dialate-erode (shrink-Grow) effect on the alpha, assuming you're using it as a mask. This can shrink the mask and cover-mask the light colors

at the edges of the shadow in the moving objects pass. Another option might be to change the background color to black in the moving objects pass.

 

What are you using to composite?

 

AE

[chow choppe]

i dont think is a bug ...it is simple and i am sure he will work it out in no time

why dont u share the solution here buddy

just writing that its "simple" will not solve the problem

 

Thanks

[chow choppe]

try rendering your car against a black background instead of blue to get rid of the edge...

yeah i made the background color similar to the road color also while compositing In AE if i click on "Guess" while selecting alpha method it does solve the problem in the areas where ther is just car shadow but its still visible in the areas where shadows are overlapping

 

also still no clue about that overlapping shaodws

Edited December 9, 2008 by 3dsmaxed

[chow choppe]

one solution wud be rendering the road and the shadows casted on it in the moving objects pass.so that atleast the shadows casted on the road and the moving car dont overlap

 

Thanks

[dpcaltdcah]

yeah, that would work, good idea. I also tried the opposite where I had no shadows at all in the moving objects pass and put car shaped objects that cast shadows but didn't render in the other pass. but for me at least the problem keeps coming up anytime I want to render anything in a separate pass; people, trees, specific buildings. we do pretty huge projects that I have to render in many pieces so it's a pain.

 

for the edges don't make the background color the road color, make it black. and then under interpret footage in AE select 'premultiplied - matted with color' and pick black as your color instead of using 'guess' that should work everywhere.

[chow choppe]

yeah, that would work, good idea. I also tried the opposite where I had no shadows at all in the moving objects pass and put car shaped objects that cast shadows but didn't render in the other pass. but for me at least the problem keeps coming up anytime I want to render anything in a separate pass; people, trees, specific buildings. we do pretty huge projects that I have to render in many pieces so it's a pain.

 

for the edges don't make the background color the road color, make it black. and then under interpret footage in AE select 'premultiplied - matted with color' and pick black as your color instead of using 'guess' that should work everywhere.

 

okay i will try that

 

thanks