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For some reason laser do not well render in homogeneous volume and even worser in heterogeneous volume.
The only safe way to get a picture like that is BiDir at the moment.

When i last played with lasers, maybe in the end on 2018, the BiDir was only one, that was able to render them.

A few first impression of my little short term project.
Street views and eagle sight of gem stone city's down town.
Best viewed open minded and mood relaxed.
I wonder how city's lime light looks like by night.


Info: openCL, PGIC, 1500 sample, approx. 19 minutes

I like the first 3.

Fox wrote: ↑Tue May 28, 2019 8:39 amI like the first 3.

Thank you for the feedback. They are also my favorites.

The glass material had to be changed because glass only lead to nothing usable.
The glass is mixed with matte (0.95 glass). Specular, transmission and matte have all the same color. I observed bright roofs but there is no light above the gem stone city. The lights emit their light vertical to the plane. I have no idea yet why the roofs are so bright.

Rainard is my favorite tone mapper. Nothing I would call straight forward usable. But hey! This Rainard algorithm rocks the colors!

openCL PGIC, OIDIN, 1500 samples, 17m28s BiDir Metropolis, OIDIN, 1500 samples, 4h54m (Still a lot to do until I am satisfied with the lights.)

Background rendering, so time does not matter much. However, it seems that more lights require more time.
openCL PGIC 1500 samples 39m29s BiDir 1500 samples 6h14m g' BiDir 1500 samples 12h23m h' (OIDIN 84% mix) PGIC 1500 samples 44m09s i The images are far away from the point I want it. Meanwhile, I made a sketch of building what is closer to my mind view. Not sure how to apply this to the other model without working a dozen hours on the objects.
openCL 1000 samples 10m06s

First the BiDir result. I take is as reference. Due to the bright floor the caustics are faint. One has to look good at them to notice the fine lines.
On the next picture you can see the effect of increasing the amount of photons. For this test series indirect and caustic have the same amount. Naturally the higher the number the more time the render takes during session initialization.
With 20 million photons one gets an image that has a steady character although with every million photons more the difference between to renders keep even from 49 to 50 millions comparable to differences between less photons.

The next animated gifs show effect of other changed parameters. As you can see this parameter changes the 'noise pattern' a bit but only randomly.
(With a count above 800 the buffer size exceeded available GPU RAM of 3'422'552'064 bytes what lead to a warning before the render started (V2.2 beta 1, build 0a863a0)). The dots of the 'noise pattern' reduces notable by decreasing this radius. The animation shows that there is happening something but it is not clear to me what exactly.

Next pictures show openCL without PGIC. Metropolis pattern on the body has obviously a lower resolution than Sobol pattern.

Last image has the parameters: 10 million photons, indirect cache radius 0.1, caustic cache radius 0.00001, max count 64.
2500 samples, 2m19s init, 8m24s render Conclusion: In comparison with BiDir PGIC fails to render the fine caustics of this body.

EDIT: I found the reason for the missing caustics. The calculation of the dispersion is wrong for this object, it is too high.

This object is obviously not a good example for caustics with PGIC.

EDIT2: Thanks to Fox Node wrong and missing camera volume I was able to fix the BiDir image. Therefore I replaced it in this post to give the correct aspects.

First I start with the less spectacular BiDir image.
Approx. 1000 samples, depth 25, metropolis, denoised 95% (mix 95% OIDN 10% raw). The next picture is based on the same file but rendered with openCL. Okay, BiDir is more colorful, but look at the render times. openCL is so amazing fast.

Further images rendered on GPU ( all following images have an external air volume with 1.5 absorption)
openCL, at least 1500 samples, depth 24 total path and glossy the others 12, denoised 90%. As one can see caustic lower look up radius leads to smoother caustics in the case of the scene.

Just for the memories, some pictures without denoiser. Rendering time openCL approx. 25 to 60 minutes depending on samples (on 2 Hawaii GPU).

Conclusion: If an object leads to hard caustics like a 'burn glass' PGIC is able to do render a very good job. And in contradiction to BiDir it renders inter- and or intra-mirroring effects or what ever leads to the much more interesting images of the lenses. And what counts even more: PGIC is much faster than BiDir (at least on my microsaurier CPU).

(As once written a combination of openCL and BiDir would be great. I think this is what PGIC is for to a certain good amount.)

EDIT: By the way, openCL without PGIC looks like.