My first Supersize-Image
Re: My first Supersize-Image
Ok here is my first little step to subsurface scattering. I have extended my bidirectional pathtracing with Homogen-Media-Support. So I have now a unbiased estimator. The next steps will be Rayleigh,Mie-Scattering and inhomogeneous media.
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- Media-Cornellbox.jpg (24.46 KiB) Viewed 1198 times
Re: My first Supersize-Image
Step 2: Rayleigh- and Mie-Scattering.
For Rayleigh-Phase-Function-Direction-Sampling I used 'Importance sampling the Rayleigh phase function from jeppe' (Inverse CDF)
For the Mie I use tabulation and the formula from 'ScratchAPixel Simulating the Colors of the Sky'
For distancesamling, I use Raab-Woodcock 'Unbiased Global Illumination with Participating Media - Raab et al (2008)'.
For the attenuation-term I use a pre-computed table. A little Idea how to implement I used the paper from Nishita 'Display Method of the Sky Color Taking into Account Multiple Scattering 1996'.
The next step is adding clouds.
For Rayleigh-Phase-Function-Direction-Sampling I used 'Importance sampling the Rayleigh phase function from jeppe' (Inverse CDF)
For the Mie I use tabulation and the formula from 'ScratchAPixel Simulating the Colors of the Sky'
For distancesamling, I use Raab-Woodcock 'Unbiased Global Illumination with Participating Media - Raab et al (2008)'.
For the attenuation-term I use a pre-computed table. A little Idea how to implement I used the paper from Nishita 'Display Method of the Sky Color Taking into Account Multiple Scattering 1996'.
The next step is adding clouds.
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- SkyRowImages.jpg (182 KiB) Viewed 1112 times
Re: My first Supersize-Image
In the next Image you can see the difference between single-scattering and multiple-scattering
Image 1: Bidirectional Pathtracing (MultipeScattering)
Image 2: Sampling a Particle-Point on the Edge from a Eye-Subpaht (Dont know the offizial name from this path-creation-sampling-routine) (MultipeScattering)
Image 3: Sampline a Particle-Point only on the edge from the Primary-Ray (Single Scattering)
Image 4: Create 20 Segments on the Primary-Ray-Edge and connect it to the sun (Single Scattering)
Image 1: Bidirectional Pathtracing (MultipeScattering)
Image 2: Sampling a Particle-Point on the Edge from a Eye-Subpaht (Dont know the offizial name from this path-creation-sampling-routine) (MultipeScattering)
Image 3: Sampline a Particle-Point only on the edge from the Primary-Ray (Single Scattering)
Image 4: Create 20 Segments on the Primary-Ray-Edge and connect it to the sun (Single Scattering)
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- SkyCompare.jpg (134.22 KiB) Viewed 1059 times
Re: My first Supersize-Image
This is the well known water-cornellbox 

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- WasserBox.JPG (210.64 KiB) Viewed 917 times
Re: My first Supersize-Image
And this the Mirror-Box. Got the idea from dawelter^^
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- MirrorBox.jpg (394.85 KiB) Viewed 900 times
Re: My first Supersize-Image
Nice progress! 

Re: My first Supersize-Image
Ok. Here is my next Participating-Media-Image: Clouds
. For the sky I use the Model from Nishita and for the clouds the cumulus-cloud-modul from David Ebert.
The images a rendered with 200 Samples per Pixel. I use lightsourcesampling on random points on the eye-path-segments and lightsourcesampling also for the eye-path-points to create a path from the camera to the light.



The images a rendered with 200 Samples per Pixel. I use lightsourcesampling on random points on the eye-path-segments and lightsourcesampling also for the eye-path-points to create a path from the camera to the light.
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- Wolken_Tag-und-Nacht.jpg (103.8 KiB) Viewed 642 times
Re: My first Supersize-Image
The next little step: Unifying Points, Beams, and Paths in Volumetric Light Transport Simulation (UPBP)
Finally after writing 435 UnitTests, to test every single Class/Sampler/SubPathSampler/FullPathSampler/PathcontributionCheck/Pdf match with Histogram-Test, I can now finally say, that I have mastered UPBP. I have written a importer for the scene-desciption-file, which are also is used in the stilllife-scene from SmallUPBP. To compare my result with a reference.
Can someone say me, what is the next step in the topic of Participating Media? Better Distancesampling? Better importancesampling durring segmentsampling?
Here is a image with 2150 samples.
Finally after writing 435 UnitTests, to test every single Class/Sampler/SubPathSampler/FullPathSampler/PathcontributionCheck/Pdf match with Histogram-Test, I can now finally say, that I have mastered UPBP. I have written a importer for the scene-desciption-file, which are also is used in the stilllife-scene from SmallUPBP. To compare my result with a reference.
Can someone say me, what is the next step in the topic of Participating Media? Better Distancesampling? Better importancesampling durring segmentsampling?
Here is a image with 2150 samples.
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- Stilliefe2150.JPG (33.29 KiB) Viewed 294 times
Last edited by XMAMan on Fri Nov 08, 2019 4:57 am, edited 2 times in total.
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Re: My first Supersize-Image
XMAMan wrote: ↑Wed Oct 30, 2019 6:59 pmThe next little step: Unifying Points, Beams, and Paths in Volumetric Light Transport Simulation (UPBP)
Finally after writing 435 UnitTests, to test every single Class/Sampler/SubPathSampler/FullPathSampler/PathcontributionCheck/Pdf match with Histogram-Test, I can now finally say, that I have mastered UPBP. I have written a importer for the scene-desciption-file, which are also is used in the stilllife-scene from SmallUPBP. To compare my result with a reference.
Can someone say me, what is the next step in the topic of Participating Media? Better Distancesampling? Better importancesampling durring segmentsampling?
Here is a image with 500 samples.
Hi,
Very nice progress, really impressed! The next big / most state-of-the-art step you can take is better: distance sampling + sampling scatter direction (phase function sampling) + better Russian roulette and possibly path-splitting! Sounds like a lot?
Check out this paper, as far as I'm concerned it's in the top 3 papers of the year:
https://cgg.mff.cuni.cz/~jaroslav/papers/2019-volume-path-guiding/index.html
For more related papers check out "Path Guiding in Production" from Siggraph this year, must read by the looks of your progress so far:
https://jo.dreggn.org/path-tracing-in-production/2019/guiding.pdf
If you're interested in "Surface Path Guiding" too after reading all that, I'd suggest checking out the links in chapter / section 10 in "Path Guiding in Production". Follow the links. "Practical Path Guiding" is a paper from 2017, but got some nice additions from a more recent paper "Neural Importance Sampling" to optimize the MIS weights during training. Don't shy away from this one, it has source code you can look at too.
Have fun!
Cheers
Re: My first Supersize-Image
He ultimatemau, thank you for you answer. All the Papers sounds good. I will look on that.