pixel filter problem

[gox570]

Hi

I just face to a trouble in my current work. this is first time I use Houdini in work, and when start render I got some problem.

the sphere and box rendered separately. when composing, you can see the edge between sphere and box is some red, the tow can't match perfectly. I thought is pixel filter setting problem but don't know how to solve. I tried every type filter in the drop menu but it still happen. if set filter to "gaussian 0 0" it will be fin and anti-alias will be disable....

I use box as a matte object for sphere. but matte is fin if I use max or maya.

 

could someone give me a idea, please?

thank you

[eetu]

Are you rendering with the red background? Don't. Render on black.

[gox570]

No. I render with black. I use red in AE just for easy to see the egde.

[eetu]

In that case it feels like you're perhaps using the wrong operator for compositing. I don't know AE, but "over" is the one that should be used here.

[theotheo]

Hi,

 

Try un-premuliting both renders, then add the two alpha's together, copy the new alpha in rgb and premult. The problem arises from both pixel edges being anti-aliased against black. You need to make sure the overlapping area has an alpha of 1.0 and not some filtered value.

 

I believe Nuke's disjoint-over does this.

[gox570]

thank your tow advices. but I still can't fix it....orz

and there is no Nuke I can use. but houdini comp has same problem. I uploaded my file and render result, hope someone know what's happen.

https://www.dropbox.com/s/h3nbxj3pxwvq3ig/renderPass.rar

 

btw, there is no one to have had this problem? my setting all is default so I thought many people would got this like me.

Edited April 22, 2014 by gox570

[eetu]

Oh, I see, you're using the box as a matte for the sphere pass.

Is there a reason you have to do that? If you rendered the sphere without the matte, it should work.

If you need the matte, then do as theotheo said

[saman]

Hi, I don't think you can get rid of this issue on the edges by increasing resolution, pixel samples or changing filter type.

here I attached the way I do separating of objects and collecting matte information of objects as separate passes in .exr format which gives a good result when you wish composting them and relighting, grading elements,

the benefit of using this way is you render your scene one time and get all passes you want in one go.

the zip is including your hip file which is edited (a houdini comp is added) ,  and a nuke composting sample is also in the zip file , hope it helps

comp.zip

[dennis.albus]

For the layer on top use the blending mode "Alpha Add". This should get rid of the edges.

 

-dennis

[gox570]

sorry, my computer just out of work and sent to repair. I'll try those advices as soon as my machine come back.

thanks!

[gox570]

wow~ thank you Saman. you created a variable for matte. it's very useful!

thanks you guys help: )