Basic Comping of a Vray render

[digtlpete]

I remember seeing a thread that disscussed this problem and Vlado said that the multiply blend mode will always create artifacts. Read this thread:

http://www.chaosgroup.com/forums/vbu...light=Multiply

I think this might answer some of your questions.

-Brian

[Seraph135]

I assume this fix is for removing halos on the edge of the objects against the background ? (pre-multiply refers to how ae handles the alpha isnt it? ) My problem actually occurs betweeen objects, so premultipying the alpha would not have any effect.

Yeah...thats exactly the situation my tip depended on. In that case I don't believe there is a fix. Multiplying will always cause that problem.

Tim J

[Da_elf]

very very very simple comp question. i usually split alpha channel from rgb when rendering however with a black background i get a black border in my AA when i go into AE and set trackmatte on the RGB image to Luma matte.

or if i have a nice bright green bottle and do the same thing the green being transparent mixes with the black and therefore the green is darker when comped. is there any way possible to get this done using alpha split

[re:FORM]

I remember seeing a thread that disscussed this problem and Vlado said that the multiply blend mode will always create artifacts. Read this thread:

http://www.chaosgroup.com/forums/vbu...light=Multiply

I think this might answer some of your questions.

-Brian

Oh thanks for that Brian, I remember reading that thread now!

So.. no solution was ever found then? We cant composite with the rawGI and rawLighting channels after all?

[vlado]

A solution would be to render at higher resolution, do the compositing with multiplication, and then downsize the result. Other than that, there is nothing that can be done.

Best regards,
Vlado

[re:FORM]

So if I, say double, the render size, would I just double the dmc noise threshold to get the same speed of render? (along with adjustinig ID and LC settings).

To rephrase... Whats the checklist of parameters to change to double a render size but retain the same rendertime ?

... that is assuming your suggestion of increasing render size can be done without adversely increasing render time ?

I'm sure I'm sounding dumb on this issue

[R_Cyph]

Vlado : what kind of resolution would u suggest to avoid these halo problems?

[vlado]

@re:FORM - each time you increase the resolution by a factor of 2, you can halve the DMC AA sampler subdivs (and perhaps increase its noise threshold twice) and decrease the irradiance map min/max rates by 1. There is no need to change the light cache.

@R_Cyph: Increasing the resolution twice should redice the edges artifacts about 4 times, whether this is enough or not, depends on the particular case.

However, all in all, it would be much simpler to not use mutliplication of render elements; just addition, which does not have this issue.

Best regards,
Vlado