caustics help

[peterguthrie]

I've searched high and low here but still can't figure this one out:

I have a pool surrounded by glass walls, if I calculate the caustics with the glass turned off, then save the solution and turn the glass back on, then the caustics in and around the pool are fine but I no longer get shadows through the glass...

Is this just the way it has to be, or is there a magic button i've missed? any help would be much appreciated!

[peterguthrie]

some images to explain:

no caustics:



hid the glass, calculated caustics:



and with caustics from file and glass unhidden:



How can I get caustics AND shadows showing through the glass?

Cheers

[nils_p]

Maybe exclude the glass fom receiving caustics?

[peterguthrie]

thanks for the reply Nils, I tried that but no change. I also tried calculating caustics with the glass visible with a very low caustics multiplier (on the glass object) but that didnt do it either.

[t3dm]

a work around would be to hide the glass, render caustic pass and then comp?

im trying to do a scene where we have a hotel pool, which has a roof with another pool above it.. its a feckin nightmare caustics wise, so using the comp'd route...

[peterguthrie]

that's what I did, but then the direct light/shadows thru' the glass didn't show (3rd image)

I guess comping it in post is the only way? If so, what's the best way of doing that? Does the vray_caustics element output something you can just add on top of the render?

[t3dm]

I used a mix of the caustics and a refraction pass, works ok.. mainly a memory problem I ran up against (very high res outputs), so thats why I went down the comp route, so I could isolate the caustics element....

[Neilg]

Whenever I do caustics I render them as a seperate pass over black and comp them in on a 'screen' blending mode onto the original render - might well solve your problem.

[t3dm]

yes I agree, the reason I used refraction is to get the caustic effects on the bottom of my pool as I was rendering a pretty crazy design (2 bloody pools, one above the other! wish most of our clients woudl just keep things simple sometimes!!)