Sketchbook: Stororokw

stororokw · May 2018

Hi! I will be using this thread to keep track of progress and to post any studies I do. I welcome critiques and comments.

stororokw · May 2018

I worked on a cloth shading model for UE4. Its based on the cloth shader from Uncharted 4. The material uses three tiling texture maps, the weave pattern, imperfections, and memory/cloth folds.
I am also making use of CharlieD.

Linen, Velvet, and Silk.

References
https://knarkowicz.wordpress.com/2018/01/04/cloth-shading/
http://advances.realtimerendering.com/s2016/

Ged · May 2018

wow lovely results! whats charlieD?

stororokw · May 2018

@Ged
"Charlie" is the name they called this sheen brdf model and the D at the end refers to just the distribution term of it.
________________
This is an anisotropic shading model I worked on for UE4 based on the shader from far cry 4.

Ged · May 2018

stororokw said:

@Ged
"Charlie" is the name they called this sheen brdf model and the D at the end refers to just the distribution term of it.

Oooh! I see...because of charlie sheen? haha! thats very nice work!

darknesz · May 2018

wow both shading models look awesome good job!!
do you have a link to the paper of the anisotropic shader?

stororokw · May 2018

Thanks guys.
Ged : Yep.

darknesz said:

wow both shading models look awesome good job!!
do you have a link to the paper of the anisotropic shader?

pages 8-21
https://www.gdcvault.com/play/1022235/Rendering-the-World-of-Far

stororokw · Jun 2018

After watching Unreal's gdc presentation I wanted to improve my implementation of skin transmission/backscatter.

I am using a phase function now, so now the scattering effect is stronger the more aligned and back facing you are with the light.

The back scattering effect now works when using a skylight.

Skylight only

Off/On

Spotlight only

Reference

https://youtu.be/_OuCrbwEJW4?t=29m11s

https://www.eisko.com/index.html

stororokw · Jun 2018

Worked on improving the eye shader since I am using an old version of UE4. Added iris normal, more pronounced caustics and fake scattering by using wrap diffuse lighting.

Vanilla UE4 eye shader on the left hand side.

stororokw · Jun 2018

Worked on a new hair shader for UE4 based on the implementation from pbrt and I also included elements from other places.

A comparison between left (UE4) and one rendered from Tungsten.

http://www.pbrt.org/hair.pdf

https://benedikt-bitterli.me/pchfm/pchfm.pdf

The hair model was downloaded from

http://www.cemyuksel.com/research/hairmodels/

stororokw · Jun 2018

Did some more work on the hair shader. I cant seem to find a value for the offset h, so I am currently using a random offset, which is the cause of the noise in the specular lobes.

Some gifs of the parameters:

BetaM - Longitudinal roughness from 0-1

BetaN - Azimuthal roughness from 0-1

Shift: shifts R, TT ,TRT along hair direction -1 to 1

bkost · Jun 2018

Dude, your shading skills are so inspirational! I wish I could understand material networks >.< How did you get started?

stororokw · Jun 2018

bkost said:

Dude, your shading skills are so inspirational! I wish I could understand material networks >.< How did you get started?

Thanks. I think you start by just looking through the existing shaders the engine provides and then play around, modify them, and then see how it affects the material. Then you can start looking through papers/presentations and implement them into the engine.

stororokw · Jul 2018

This is how the hair shader reacts under camera motion.

stororokw · Jul 2018

Started learning DirectX and C++. Going to post the resources I use if anyone wants to follow along.

Reference:

https://www.3dgep.com/introduction-to-directx-11/

stororokw · Jul 2018

Went through the "official" DirectX tutorials from Microsoft. Everything is still confusing, but hopefully it will start to click together.

Reference

https://code.msdn.microsoft.com/windowsdesktop/Direct3D-Tutorial-Win32-829979ef#content

stororokw · Sep 2018

So its been exactly two months since my last post. I have been slowly going through two of the recommended DirectX books in my spare time. I still haven't completed them yet, but I think I've made some progress worth showing from my previous post.
https://blogs.msdn.microsoft.com/chuckw/2014/04/07/book-recommendations/

References
Introduction to 3D Game Programming with Direct3D 11.0 by Frank Luna
Real-Time 3D Rendering with DirectX and HLSL: A Practical Guide to Graphics Programming by Paul Varcholik

stororokw · Sep 2018

Spent most of my time debugging. Currently trying to get projective texture mapping and shadow mapping working.

stororokw · Oct 2018

I started working on atmospheric scattering. Currently its full of bugs, but its nice to see something resembling the sky. I have not been able to figure out how multiple scattering, direct/ambient lighting or shadows fits into the puzzle yet and its hard to tell if what I have so far is even correct.

Sun Disc from left to right: without anything, with limb darkening, and with limb darkening + transmittance.

References
youtu.be/zs0oYjwjNEo?t=1h17m58s
https://www.ea.com/frostbite/news/physically-based-sky-atmosphere-and-cloud-rendering
http://cgg.mff.cuni.cz/~oskar/projects/Theses/BScThesis_OskarElek.pdf
http://publications.lib.chalmers.se/records/fulltext/203057/203057.pdf
https://www.gamedevs.org/uploads/deferred-rendering-of-planetary-terrains-with-accurate-atmospheres.pdf
https://www.alanzucconi.com/2017/10/10/atmospheric-scattering-1/

stororokw · Oct 2018

I have been working on rendering volumetric clouds.

Previewing slices of a 3D texture.

stororokw · Oct 2018

Rendering stars from HYG database as sprites this allows you to fly through them which a static image doesnt allow. I need to figure out how to blend it with the atmosphere though so it doesn't show through the clouds... not really sure how yet since it is rendered with a separate shader.
Still needs glare, and some nebulae.

http://www.astronexus.com/node/34/

stororokw · Oct 2018

Some progress on the volumetric clouds, hopefully looking more cloud like.

https://www.youtube.com/watch?v=Sm78XUjVNw0

stororokw · Jan 2019

Revisited the hair shader

Added tangent based controls in the material editor (shift, rotation and direction).
Changed the skylight calculations.

Added two flavours of shift. One shifts along the tangent direction. The other control is the analogue to normal map I added an option to either use a tangent map for it or automatically derive it from the normal map.

As a tip when placing hair cards in maya you can use the hair tube shader and set it to v-tangent to visualize the flow of the specular highlight. This reduces the back and forth between maya and ue4.

I still need to get the glints working correctly.

stororokw · Jan 2019

real time hair test in ue4. 7k triangles.

stororokw · Jan 2019

Probably finished with this hair study. Came out to 7.5k triangles in the end and 2k textures. For those interested I post the splines.

stororokw · Jan 2019

Another quick hair study wip. Chin length bob with see-through bangs. 5k triangles.

stororokw · Feb 2019

I started learning marvelous designer. I focused on understanding sewing and patterns and how they are constructed in real life. These are exported straight from md into ue4. I find that some of the creases that appear in real life around the butt and horizontal creases do not appear in the simulation... does anyone have any tips on how to get them to appear?

stororokw · Feb 2019

I have been learning about the different types of collars and sleeves in marvelous designer.

stororokw · Mar 2019

Worked on some hair related stuff again.

Moved the rotation and shift controls to the material instead of the shader.
Added blur to the hair. This helps remove some of the dithering, improves the transition to the head, is cheaper than using translucency, and overall, softens the hair, but some of the details get lost.

Sheer cloth material using opacity mask. Good for curtains, panthose, and sheer fabrics.

Serejka · Apr 2019

stororokw said:

After watching Unreal's gdc presentation I wanted to improve my implementation of skin transmission/backscatter.
I am using a phase function now, so now the scattering effect is stronger the more aligned and back facing you are with the light.
The back scattering effect now works when using a skylight.
Skylight only
Off/On
Spotlight only

Reference
https://youtu.be/_OuCrbwEJW4?t=29m11s
https://www.eisko.com/index.html

Hm, any chance to see a shader implementation on Github or breakdown on this phase function, working with Skylight?

stororokw · Apr 2019

I don't have the original code anymore since it was for an old version (4.16) and they implemented transmission since 4.20, so its probably better to use that.
https://docs.unrealengine.com/en-us/Resources/Showcases/DigitalHumans#skinshading

The code below should be added into SkyLighting.usf. I haven't tested this, so you need to do some modifications to get this compile and operate as intended. Thickness is the value from your thickness texture.

        float g = -0.25;
        float p = (1 - (g * g)) / (4 * PI * pow(1 + (g * g) - (2 * g * dot(V, L)), 1.5));
        Lighting += p * Thickness * (1 - SkyVisibility) * dot(V, SkyLightingNormal) *
                    saturate(1 - DiffuseLookup) * TT(Thickness);
    }
}// from <a rel="nofollow" href="http://www.iryoku.com/translucency/">http://www.iryoku.com/translucency/</a>
float3 TT(float s)
{
    return float3(0.233, 0.455, 0.649) * exp(-s * s / 0.0064) +
         float3(0.1, 0.336, 0.344) * exp(-s * s / 0.0484) +
         float3(0.118, 0.198, 0.0) * exp(-s * s / 0.187) +
         float3(0.113, 0.007, 0.007) * exp(-s * s / 0.567) +
         float3(0.358, 0.004, 0.0) * exp(-s * s / 1.99) +
         float3(0.078, 0.0, 0.0) * exp(-s * s / 7.41);
}
 
void SkyLightDiffusePS(...)
...
    if(ShadingModelId == SHADINGMODELID_SUBSURFACE_PROFILE)
    {
        ...
        float Thickness = ...;

Serejka · Apr 2019

stororokw said:

I don't have the original code anymore since it was for an old version (4.16) and they implemented transmission since 4.20, so its probably better to use that.
https://docs.unrealengine.com/en-us/Resources/Showcases/DigitalHumans#skinshading

The code below should be added into SkyLighting.usf. I haven't tested this, so you need to do some modifications to get this compile and operate as intended. Thickness is the value from your thickness texture.

        float g = -0.25;
        float p = (1 - (g * g)) / (4 * PI * pow(1 + (g * g) - (2 * g * dot(V, L)), 1.5));
        Lighting += p * Thickness * (1 - SkyVisibility) * dot(V, SkyLightingNormal) *
                    saturate(1 - DiffuseLookup) * TT(Thickness);
    }
}// from <a rel="nofollow" href="http://www.iryoku.com/translucency/">http://www.iryoku.com/translucency/</a>
float3 TT(float s)
{
    return float3(0.233, 0.455, 0.649) * exp(-s * s / 0.0064) +
         float3(0.1, 0.336, 0.344) * exp(-s * s / 0.0484) +
         float3(0.118, 0.198, 0.0) * exp(-s * s / 0.187) +
         float3(0.113, 0.007, 0.007) * exp(-s * s / 0.567) +
         float3(0.358, 0.004, 0.0) * exp(-s * s / 1.99) +
         float3(0.078, 0.0, 0.0) * exp(-s * s / 7.41);
}
 
void SkyLightDiffusePS(...)
...
    if(ShadingModelId == SHADINGMODELID_SUBSURFACE_PROFILE)
    {
        ...
        float Thickness = ...;

Hm, it's non normalized Henyey-Greenstein phase function (p with define g=-0.25 (why exactly -0.25?) == < 0 meaning backward scattering), thanks!

stororokw · Apr 2019

I think it should actually be forward scattering... most likely the light vector, L, on line 19 should be negated, g should be positive and set somewhere between 0.25 to 0.5. These values were obtained visually because the transmission effect doesn't really show up too well otherwise. I guess at the time I felt 0.25 looked okay.
Below I show g ranging from 0.25 to 1.

Serejka · Apr 2019

and what about your old transmission? https://vimeo.com/253638469
what technique was in this example?
Thank you for the detail explanations!

stororokw · May 2019

I think that video was pretty early on, so I cant remember the details of it. I ended up using http://www.iryoku.com/translucency/ for inspiration.
You can use the shadow depth information from ShadowProjectionPixelShader.usf to approximate the distance, which gets passed to the shading model.

Serejka · May 2019

stororokw said:

You can use the shadow depth information from ShadowProjectionPixelShader.usf to approximate the distance, which gets passed to the shading model.

Basically the current UE4 implementation of transmission, right?

stororokw · May 2019

I haven't looked through the implementation, but I believe so. I think unity also use a similar approach and it looks better.

stororokw · Jun 2019

I wanted to get some real world reference of the sky so I can do some comparisons later on. I ended up using the fisheye images from the NREL Solar Radiation Research Laboratory (SRRL). The image quality isn't great and there are missing images from the datasets, but I cant find any better sources.
I used Paul Bourke's site for learning about the fisheye projection and its conversion to a perspective projection.
Ended up using DirectX 11.

https://www.youtube.com/watch?v=608FqvXUOfk
https://midcdmz.nrel.gov/apps/sitehome.pl?site=SRRLASI#
http://paulbourke.net/dome/fisheye/

stororokw · Jul 2019

Ported Bruneton's atmospheric scattering to DX11 using compute shaders and setup the camera so it always matches up the reference sky for doing comparisons. It seems to really struggle with the blues regardless of the time of day producing this unnatural green looking sky. Need to find out what is causing this.

Reference
http://www-evasion.imag.fr/Membres/Eric.Bruneton/

stororokw · Jul 2019

Converse Low top high poly ZBrush WIP

stororokw · Jul 2019

Converse low poly
Worked on the retopology of the high poly. Is the topology good enough? What could be improved?

stororokw · Jul 2019

I was playing around with the different parameters of the atmosphere shader and while I was able to get somewhat close to my references it was still far off. Instead of endless tweaking, I added non physically based parameters to control the overall appearance.
But, It still struggles pretty hard during the twilight/'blue hour' period.
Morning:

Late afternoon:

stororokw · Jul 2019

Quick and dirty normal map test. Currently just using the auto unwrap from zbrush and slapping on some presets from substance painter to test out the low poly.

stororokw · Aug 2019

I went through 'Ray Tracing In One Weekend' by Peter Shirley. It's a free introductory book to ray tracing that doesnt assume any prior knowledge. This implementation uses DirectX11 compute shaders to render the image.
http://in1weekend.blogspot.com/2016/01/ray-tracing-in-one-weekend.html

https://www.youtube.com/watch?v=G8XwW-eFlLM

stororokw · Aug 2019

Following the book 'Ray Tracing : The Next Week'
http://in1weekend.blogspot.com/2016/01/ray-tracing-second-weekend.html.
Had a hard time implementing the bounding volume hierarchy, which is an acceleration data structure that speeds up the intersection testing, since there is no recursion in hlsl.

https://www.youtube.com/watch?v=YkxBEEJTFmI

stororokw · Aug 2019

Implemented textures described in chapters three and five of the book.

https://www.youtube.com/watch?v=Wgbzv--ofeE

stororokw · Oct 2019

Worked on a real time approximation for area light shadows using standard shadow mapping by stochastically sampling the area light and using the generated sample point for depth comparison instead of the light's center point.

https://www.youtube.com/watch?v=0OJby2rLDZA

stororokw · Apr 2020

I started working on a physical camera and currently focusing on the depth of field and bokeh.
A comparison between real life. Light source is 5mm in diameter at a distance of 3m, focus distance is 1.5m and focal length is 200mm. The real life images were taken from the slides of "Basic Implementation of Bokeh" since I don't have a dslr camera to validate with.

Reference
https://research.tri-ace.com/s2015.html

stororokw · Apr 2020

For the past couple days I have been trying to understand the fourier transform. One of its applications is faster convolutions and also being able to approximate the diffraction of waves through an aperture typically seen as glare on an image.

The bottom shows the amplitudes after applying the fourier transform on apertures with a varying number of blades. We see that there are twice the number of spikes if the number of blades is odd.

In the image below the size of the aperture is changed and the blade count is kept the same. More diffraction occurs when the aperture is smaller, but the amplitude decreases because less light makes it through.

To simulate the glare effect we perform a convolution using the kernel and image. The bottom half shows the generated glare effect.

The images are currently being generated on CPU with a naive discrete fourier transform algorithm so, it unfortunately takes minutes to compute and is monochromatic.

References

https://www.youtube.com/watch?v=spUNpyF58BY (3Blue1Brown)

https://www.youtube.com/watch?v=mkGsMWi_j4Q (Simon Xu)

http://www.jezzamon.com/fourier/

https://betterexplained.com/articles/an-interactive-guide-to-the-fourier-transform/
https://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm

stororokw · May 2020

Made some progress with the GPU based implementation of convolution FFT bloom, still lots of things left to do.

Currently it is limited to monochromatic light for the diffraction through the aperture.
Still need to figure out how to create artist friendly parameters to change the appearance of the glare.
Needs to be incorporated into actual 3d scene instead of static loaded image from disk.

References
http://www.bealto.com/gpu-fft2.html
https://www.youtube.com/watch?v=SkJgopq-JQA

stororokw · May 2020

I managed to get the the diffraction pattern of the apertures working for the visible light spectrum.

Reference
http://nishitalab.org/user/nis/cdrom/pg/glare_m.pdf

Sketchbook: Stororokw

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