Caustics And Animation
Sockratease
Posts: 813
Ug. Does anybody know if caustics are inherently animated all by themselves?
I have a scene I was animating and noticed the caustics were moving about as if it was on water, but was actually being used on "metal" and I didn't expect that behaviour.
I have set up caustics before, though I don't recall ever making an animation with them set rather high. I thought it was the stuff moving around interfering, so I duplicated the lights and set the originals to the moving objects only and the duplicates to everything but the moving stuff. I thought that may tame things, but no effect.
Is there a way to tame the caustics to be consistent frame to frame?
I know caustics aren't totally random because I have done many test renders at low resolution and gotten consistent results every time I scaled up, so I don't understand what is happening here.
I may need to do some fancy layering and masking in the video since I find the caustics move about far too much and are distracting. Unless anybody has any information that may help?
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Comments
I doubt it could be faked with a gel because it's the color enhancing I was going for.
Here's a picture:
The angel swoops by blowing the horn and the caustics literally move as if I'm animating the light source the whole time. The light is motionless and unvarying, and reduced to one source for confirmation. It looks cool on the rosettes on the pillars, but is way out of place on the stairs and the pool.
Sumpin' unexpected is going on...
Something is definitely amiss with the render. I don't see any cows. Who are you, and what have you done with Sockratease?!
Didn't you hear?
I had to take a job making a website for a religious group to help with my wife's medical bills.
I did manage to talk them into adding some animations interspersed in their lecture videos to make them more watchable. They had a guy at a podium with an unmoving camera for 30 to 45 minutes, and I saw an opportunity to pad the bill!
Sound more like the real me?
I'd do anything for the woman I love. Even work for churches making websites with messages I don't approve of, and rendering images with human figures and no cows anywhere on camera!! (There may be some off camera playing with sex toys, but they're off camera so god will never know...)
OK. I figured this out.
I removed the angel totally and the caustics are stable. They are just hypersensitive! Even when the moving object has zoomed through the arches in the background, the caustics go nuts.
I'm going to have to do a few passes and composite - one single still for the background, then an object pass for the demon or angel or whatever it is, and another shadow pass so that part works too.
I am surprised the caustics are as sensitive as they are to any distant motion, but it is what it is and I have a work-around, so DAZ will be happy enough to consider this case closed
I dunno...
I might have expected a reaction, but the disco ball full-blown spinning was a lot more of a reaction than I ever would have thought possible. Even after the figure was far away, it's motions effected every caustic in the scene heavily.
If I ever finish this job I'll see about posting a short video of the results from both methods (composited, and all-at-once). It struck me as so far over the top that I really thought the caustics themselves had to be animated. One day I should substitute a clay shaded sphere for the angel to see if it was the "metal" on the figure, or it's mere presence. But first I gotta make some monies!
I did a quick animation and made a movie of the caustics pass, and it seems to animate okay as far as I can tell. Although maybe different elements in the scene might cause some caustics problems...not sure.
By the way, one benefit of looking only at the caustics pass is that you can see how relatively simple the caustics effect can be. In the video I posted, really it looks just like a white patch that is animated by noise or something.
So one option, if it works for you, is to generate a caustics pass in a 2D/compositing app rather than waiting for a 3D render. It also gives you a lot of control over the effect.
Just a thought.
Thanks for trying a test Joe.
I made a quick mini gif to show what happens.
Your test is interesting, but doesn't mimic the conditions of the picture posted. Watch the base of the pool in this image - it was just a quick test render to see how it would look and the caustics never stop quivering even after the angel is well past the set.
No light changes or moves and no off screen cows are making whoopie or anything (saving that for the final render
) so I really have no explanation...
EDIT = my gif isn't animating from here!
It works offline, but is 200 frames (though under the file size limit)
Will make a video this weekend.
And I settled for a still background and a shadow pass with a solo angel layer and will composite it all together.
Yeah, I was merely responding to the question you asked: "Does anybody know if caustics are inherently animated all by themselves?". From my test it seems that, in general, the caustics are solving correctly and following the motion of the light that generated them. Again, YMMV depending on your scene I suppose.
Honestly I couldn't tell from the image you posted what caustics were present. And the GIF you just posted is too small and doesn't seem to be animating. So I'm really not sure what is your specific issue.
yup - was editing when you posted.
The effect really is exaggerated and worth seeing.
I'll make a video over the weekend when playing with the passes I rendered out.
I think the problem is that caustics in Carrara are photon map based and like in any animation with GI (photons) there will be random changes depending where object in the scene is.
Carrara in GI tab does have option to use same map for entire animation (which eliminates random generation of photons) but this only generates correct render if camera is the only object moving ...
I think you are out of luck here and maybe you should consider ditching caustics entirely (if they are not absolutely necessary), or, like already suggested, play with different passes in compositing software and see what happens
Well, I did test the scene by rendering it with no moving anything, and the caustics stayed stable. So it's definitely reacting to movement. I'd rather not lose the caustics because they really enhance the color of that reflecting pool. See the highlights at the base? The orange stuff? That is from the caustics and gets lost without them. So as I said, I settled for a still background and 2 other passes - one for the figure rendered with alpha, and another shadow pass for compositing.
Will still need some fancy layering since the thing flies over the stairs and through the arch to the right in the background. This looks like it will work, but wont have time to test it until tomorrow or sunday.
Definitely some high weirdness going on. As an old hippy I normally embrace High Weirdness - but not when it interferes with paying work!
I'm still baffled at what you're referring to as "caustics". I don't see anything obvious in the image you posted. I see reflections, but I'm not sure exactly what would be generating caustics and where they are in the image.
It would be interesting to have just one render with a separate caustics pass to see what the caustics are.
Look again. More closely this time and pay attention only to colors and not forms. Maybe that will help.
Look at the base of the "pool" - see the gold color? That is the stock "Meta l: Electrum" shader. Now see the orange below the "rim" of it? That is the caustics.
See the rosettes on the pillars? The Whitish color under the tulipy bits is a rose something-or-other shader, but the glowy orangy bit is the caustics! Here's the pic again so you don't have to strain anything scrolling back and forth between posts:
There are also subtler bits of it all over the image, but they are subtle.
Try to let go of your obsession with realism. This render is about religious stuff - angels and such - nothing to do with reality