caustics again.

V-Ray V-Ray for 3ds Max General
1

as mentioned recently its pretty futile to try and use caustics for a pool shot, far better to use a fake effect.

so, naturally, im trying yet again with real caustics.

however its been so long im probably missing something.

i enable caustics, and crank up the caustic subdivisions of my lights (a few directional vraylights above the pool)

it spends all of .5 seconds on the caustics calc. and i get no caustic effect at all, even with the multiplier at 100.

id imagine id get -something- even if the settings are off.

what am i missing? ive got gi disabled, but that shouldnt affect it right?

ive tried light caustic subdivs up to 600,000 and it still does an instant caustics calc and no result.

2

Make sure that Affect shadows option is Off for the refractive material.

3

Make sure that the “Affect shadows” option for your water material is OFF.

The sunlight needs to be as focused on the pool as possible. Set the caustics search distance to something like 2cm, the max density to 0.2cm, and the max photons to 0, and see if anything comes out.

Best regards,
Vlado

4

affect shadows is off on all materials.. all 8 caustics generating lights are focused down on the pool from directly above.

scene is in metres, so default caustic settings are 5 metres search distance.

5

So can you post the scene here?

Best regards,
Vlado

6

ok so changing caustics settings to 2 metres search distance and 0.2 metres max density has caused it to start calculating a slow caustics map as expected.

i didnt realise the settings as default could cause it to not generate -anything-

7

i could upload scene to you but its the initial phase of an architectural competition, so it would have to be kept private.

to be honest id be interested to see if you could actually manage to get a reasonable caustic result in a pool.. ive nver seen anyone manage it.

always have to fall back on projector maps but they are fiddly to get looking ok.

8

Well, alternatively I can do a quick scene for you… let me see.

Best regards,
Vlado

9

ok picture a full size indoor swimming pool with 8 large tubes punched through the cieling letting daylight in. ive put a rectangle light at the top of each tube with a directionality of .6.. they are about 1m x1m, and the pool is about 30m long.

10

ok so latest result is it spends 10 mins calculating the caustics map, the the vray log window states "photons stored : 0 " map size : 0mb

11

im sending you a stripped scene… vlado@chaosgroup ok?

12

Yep, vlado@chaosgroup.com

Best regards,
Vlado

13

Here is a quick test. I will look at your scene in a moment too.

Best regards,
Vlado
pool_caustics.zip (41 KB)

pool_caustics.jpg
pool_caustics.jpg640×480 57.3 KB

14

thanks vlado, ive had some success in scenes like that ( caustics only underwater, single point light source)

-in my, and most other cases, its the reflected caustics i really need (on the ceiling/walls) , plus the lighting is from multiple sources with more area.

-one issue in the past has always been refracted caustics being much much brighter than reflected ones, with no way to control the balance between the two.. to get the caustics on the cieling the correct brightness, the ones underwater have to be thermonuclear.

could i do something with mtl override here?

in any case, id be happy just to get -some- caustics in my scene!

15

I think caustics reflected around the room just don’t happen that much in real life, which is why yours are barely visible/not showing up.
It’s a nice looking thing that everyone puts in renders, but if you look for photos of indoor pools (I just did a google search) I could only find one image that had any - and with the rest of the room lit up they were barely visible. for the most part you just some soft blue light from the underwater lights spilling out.
Have you tried rendering caustics as a separate pass and brushing them into area with a mask? think thats the only way you’ll get the control needed to have the reflected ones as bright as we like.

16

The problem for the scene was that the water was set to invisible for GI, and also as not shadow casting. Once I enabled these options, the caustics appeared, but they don’t really do anything interesting - the light sources just produce quite a bit of ambient light, which is not focused anywhere. If I create a single small sphere light and add some more interesting bump pattern on the water, I can get something more interesting, but I guess that’s not the point :slight_smile:

Best regards,
Vlado