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Badriel

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Posts: 10
Reply with quote  #1 
Hello,
I'm new to su podium and I noticed the caustics almost always look pretty bad, and the lack of tutorials made me make one myself.
I've lately worked a bit to understand the nature of caustics in su podium, and came with results. To make caustics look better in podium you'll need to edit some values in one of your presets.
I'll try to explain these values the best I can, though some of them are still unclear to me. If there's someone who has got a better understanding of these values, I hope they'll share their secrets. I read the preset guide, but it was, unfortunately, very lacking.


var __cphotons: increases the amount of photons and decreases their size. The bigger value, the better outcome. Greatly affects the performance. If you're aiming for a scene with very soft caustics, and want them to be quick, turn it to -30 and set cmult to 2.
var __cN, blurs the photons. Increasing the value makes things less blotchy, but also  impacts the performance. 
var __cmult, increases intensivity of the light. Has no effect on the performance.
var __csteps, Can't really tell what it does. Changing the values showed no difference in the outcome. Has no effect on the performance.
var __clow, higher value increases the blur on photons, setting it to 0 removes the blur from edges of reflected light. Has some impact on the performance. Lower values merge the photons into 'blotches'.
var __chigh, Has a similar effect to the value above, and they're somehow connected, but I can't figure out how yet. It seems it affects the high-contrast photons and merges them. Increasing this value might heavily impact the performance 




And some examples of editing each of the values:

First, the default values:
http://i.imgur.com/ehHoLDW.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0.9;

http://i.imgur.com/5rj3JpX.jpg
var __cphotons, -1000000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0.9;

http://i.imgur.com/KAnjNQt.png
var __cphotons, -100000;
var __cN, 60000;
var __cmult,1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0.9;

http://i.imgur.com/zRzosJd.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,5;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0.9;

http://i.imgur.com/WOyPZk6.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 10;
var __chigh, 0.9;

http://i.imgur.com/ehHoLDW.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 0;
var __chigh, 0.9;

http://i.imgur.com/IwrryXG.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0;

http://i.imgur.com/EMkXLUM.jpg
var __cphotons, -100000;
var __cN, 600;
var __cmult,1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 10;


And now some useful presets:
A preset mostly for people who want very smooth reflections without worrying about performance:
http://i.imgur.com/UArn0mb.png
var __cphotons, -30;
var __cN, 300;
var __cmult,2;
var __csteps,10;
var __clow, 1;
var __chigh, 0.1;

A nice caustics effect, though a bit blotchy and affects the performance a bit:
http://i.imgur.com/hGWFGFq.jpg
var __cphotons, -2000000;
var __cN, 30000;
var __cmult,1.1;
var __csteps,10;
var __clow, 0
var __chigh, 0;


A very accurate effect, but grainy. And the camera tracing will take a very, very long time:
http://i.imgur.com/G8mBztr.jpg
var __cphotons, -6000000;
var __cN, 3000;
var __cmult,1.1;
var __csteps,10;
var __clow, 0
var __chigh, 0;

The best result I could come up with without a great impact on the performance. It's pretty accurate and rather smooth. Camera tracing takes a very long time, unfortunately. And the blotches are still there.
http://i.imgur.com/CGZHxxN.jpg
var __cphotons, -6000000;
var __cN, 30000;
var __cmult,1.1;
var __csteps,10;
var __clow, 0.1;
var __chigh, 0.9;
davew

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Posts: 1,572
Reply with quote  #2 
Wow. I have to try this out.
BTW - the next upgrade is Version 2Plus and it has a Preset Editor which will make editing presets a bit simpler.
bigstick

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Reply with quote  #3 
Thanks for testing these! As you have seen, I haven't spent much time tweaking caustics, because the results I had in my tests with the default values were all better than yours with the standard presets. However, it does show how results can vary a lot from one scene to another. This is the critical thing, because caustics seem to be much more sensitive to different values than photons.

The cN value does indeed blur the photons together to get a smooth appearance. There is more information here:- http://www.kraytracing.com/archive/manual/caustics/index.php
It's rather old now, and doesn't relate precisely to the Podium variables, but the the principles remain the same.

The variable cLow is equivalent to the Radius value, and cHigh is the Max value.

We do have some newer presets with the next version of Podium that improve caustics.

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Badriel

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Posts: 10
Reply with quote  #4 
Oh, that's good to know. I don't really understand how the options work, it was just a tedious, long experiment of changing every value and see how things respond. The manual you posted made some things clearer, but still, I'm pretty far from satisfying results. I can't wait for the next version of Podium. I'd love to see the autophotons mentioned in the manual too.
bigstick

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Reply with quote  #5 
I thought autophotons were configured, but I'm not so sure now.

When I first started using the Kray engine, none of the variables were even named, there was just long lists of numbers in the script lines

So, yeah, I know exactly how tedious this process is! 

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Collin045

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Posts: 1
Reply with quote  #6 
The detail your are showing is a section of all the red lines, repeated 6 times vertically? For those type of thing I would have normally simply painted a red LEM instead of the translucent glass. But what you did makes a more diverse effect, less flat-  the edges are more visible. This is cool. 
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DavorP

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Reply with quote  #7 
Copying a random post from another, by accident my thread, and posting it somewhere else. What are you trying to achieve? If you post some spam, you will get banned.
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