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KHR_materials_diffuse_transmission #1825

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merged 27 commits into from
Nov 18, 2024
Merged

KHR_materials_diffuse_transmission #1825

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5c78221
Initial draft for KHR_materials_translucency.
proog128 Jun 9, 2020
581f024
Added figure and code to describe BTDF.
proog128 Aug 4, 2020
db5aecc
Update KHR_materials_translucency
bsdorra Jan 14, 2021
e3d5468
README.md edited
bsdorra Jan 14, 2021
dbd0f34
Change summary images; Add review changes
bsdorra Jan 15, 2021
ed933ab
Merge branch 'KHR_materials_translucency' of ssh://eu-muc-git01.ux.ds…
bsdorra Jan 15, 2021
c99b6c7
Change thin transmission image; Fix font
bsdorra Jan 18, 2021
6d8e1f2
Change summary images; Add review changes
bsdorra Jan 15, 2021
a00be41
Add translucency color parameter and examples
bsdorra May 6, 2022
1af7abe
Minor updates
bsdorra May 6, 2022
25ca3c9
Optimize example image format/size
bsdorra May 6, 2022
c8ce712
Add example description; Update brdf notation
bsdorra May 6, 2022
a3ea22b
Rename translucency -> diffuse_transmission
bsdorra May 6, 2022
5c66d6c
Change example table layout, edit descriptions
bsdorra May 9, 2022
cfb298b
Update extensions/2.0/Khronos/KHR_materials_diffuse_transmission/sche…
bsdorra Jun 20, 2022
097b8b7
Remove example for combined diffuse-/transmission
bsdorra Jun 23, 2022
70ff0da
Remove all references to KHR_materials_sss
bsdorra Jun 23, 2022
5e78cfc
Remove extensions combination overview for now
bsdorra Jun 23, 2022
74cebc5
Update image text
bsdorra Jun 16, 2023
105b508
Fix typo
bsdorra Jul 25, 2023
4e22210
Revise spec
bsdorra Jun 18, 2024
36c6bbb
Fix image table layout. Add white bg to bsdf image for better visibil…
bsdorra Aug 2, 2024
95892f4
Split up normative "material structure update" and non-normative impl…
bsdorra Nov 8, 2024
81ae540
Fix Appendix B url
bsdorra Nov 8, 2024
2e3de3e
Add exclusions; Add scene/texture attribution
bsdorra Nov 14, 2024
3d93731
Use https uri
bsdorra Nov 14, 2024
543ce36
Remove leaves image
bsdorra Nov 18, 2024
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34 changes: 26 additions & 8 deletions extensions/2.0/Khronos/KHR_materials_diffuse_transmission/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,6 @@
* Bastian Sdorra, Dassault Systèmes [@bsdorra](https://github.com/bsdorra)
* Ed Mackey, AGI [@emackey](https://twitter.com/emackey)

TODO
## Acknowledgments

TODO

## Status
Expand All @@ -19,6 +16,11 @@ Experimental

Written against the glTF 2.0 spec.

## Exclusions

* This extension must not be used on a material that also uses `KHR_materials_pbrSpecularGlossiness`.
* This extension must not be used on a material that also uses `KHR_materials_unlit`.

## Overview

This extension models the physical phenomenon of light being diffusely transmitted through an infinitely thin material. Thin dielectric objects like leaves or paper diffusely transmit light due to dense volumetric scattering within the object. In 3D graphics, it is common to approximate thin volumetric objects as non-volumetric surfaces. The KHR_materials_diffuse_transmission extension models the diffuse transmission of light through such infinitely thin surfaces. For optically thick media (volumes) with short scattering distances and dense scattering behavior, i.e. candles, KHR_materials_diffuse_transmission provides a phenomenologically plausible and cost-effective approximation.
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In the caption for the leaves and candle, we use the term "translucent" rather than diffuse transmission. Could this be confusing to readers? Perhaps, we could change "translucent surface" to "diffusely-transmitted surface" or something? I'm assuming that the term "translucent" is a holdover from the previous name for this extension.

Expand All @@ -29,7 +31,11 @@ This extension models the physical phenomenon of light being diffusely transmitt
<img src="figures/leaves.jpg" height="350" />
<img src="figures/candle_0.5.jpg" height="350" />
</p>
<figcaption><em>Left: (Thin) translucent leaves/foliage, Right: (Thick) translucent candle with colored volume attenuation and translucent surface.</em></figcaption>
<figcaption>
<em>Left: (Thin) translucent leaves/foliage, Right: (Thick) translucent candle with colored volume attenuation and translucent surface.
</em><br>
<p style="font-size:0.7em;">(candle model by <a href="https://sketchfab.com/lucatorcigliani">lucatorcigliani</a> with modifications by @emackey. Original <a href="https://sketchfab.com/3d-models/candle-in-a-glass-ec6cf358c4dd4cbda7be67f7846cbc9e">source</a> CC-BY 4.0)<p>
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</figcaption>
</figure>
</div>

Expand Down Expand Up @@ -168,7 +174,11 @@ diffuseTransmissionColor = diffuseTransmissionColorFactor * diffuseTransmissionC
</tr>
<tr>
<td colspan="5" align="center">
<em>Single-sided plane in a symmetric light setup. <code>baseColorTexture</code> and <code>diffuseTransmissionColorTexture</code> use textures that represent the different sides of the one-dollar bill. Series shows the setup at varying values of <code>diffuseTransmissionFactor</code>.</em>
<em>
Single-sided plane in a symmetric light setup. <code>baseColorTexture</code> and <code>diffuseTransmissionColorTexture</code> use textures that represent the different sides of the one-dollar bill. Series shows the setup at varying values of <code>diffuseTransmissionFactor</code>.<br>
<p style="font-size:0.7em;">(dollar bill texture from <a href="https://resourceboy.com/textures/dollar-textures/">ResourceBoy.com</a> )
<p>
</em>
</td>
</tr>
</table>
Expand Down Expand Up @@ -354,7 +364,10 @@ diffuse_bsdf = mix(
</tr>
<tr>
<td colspan="5" align="center">
<em>Dragon with fixed <code>diffuseTransmissionFactor</code> of 1.0 and varying <code>transmissionFactor</code>.</em>
<em>Dragon with fixed <code>diffuseTransmissionFactor</code> of 1.0 and varying <code>transmissionFactor</code>.<br>
<p style="font-size:0.7em;">
(dragon model from <a href="http://graphics.stanford.edu/data/3Dscanrep/">Stanford 3D Scanning Repository</a>)
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</em>
</td>
</tr>
</table>
Expand All @@ -375,7 +388,9 @@ When `KHR_materials_diffuse_transmission` is combined with `KHR_materials_volume
</tr>
<tr>
<td colspan="3" align="center">
<em>Dragon with white base color, colored volume attenuation and varying <code>diffuseTransmissionFactor</code>. </em>
<em>
Dragon with white base color, colored volume attenuation and varying <code>diffuseTransmissionFactor</code>.<br>
</em>
</td>
</tr>
</table>
Expand All @@ -393,7 +408,10 @@ When `KHR_materials_diffuse_transmission` is combined with `KHR_materials_volume
</tr>
<tr>
<td colspan="3" align="center">
<em>Candle with off-white base color, colored volume attenuation and varying <code>diffuseTransmissionFactor</code>. </em>
<em>
Candle with off-white base color, colored volume attenuation and varying <code>diffuseTransmissionFactor</code>.<br>
<p style="font-size:0.7em;">(candle model by <a href="https://sketchfab.com/lucatorcigliani">lucatorcigliani</a> with modifications by @emackey. Original <a href="https://sketchfab.com/3d-models/candle-in-a-glass-ec6cf358c4dd4cbda7be67f7846cbc9e">source</a> CC-BY 4.0)<p>
</em>
</td>
</tr>
</table>
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