MetalByTutorials/references.markdown at main

4.7 KiB

Raw Permalink Blame History

Physically Based Rendering

Allegorithmic: The Theory of Physically-Based Rendering and Shading

SIGGRAPH University - Introduction to "Physically Based Shading in Theory and Practice" by Naty Hoffman

Create your own skybox textures

1. Find a texture

Find an equirectangular environment map. This is a texture which has the full 360º view projected onto it.

Sources of environment maps:

http://hdrihaven.com 100% free and licenced CC0

http://www.hdrlabs.com/sibl/archive.html free, but licenced as Creative Commons Attribution-Noncommercial-Share Alike 3.0.

Using your own pictures:

Download Google StreetView app. Find an uncrowded place such as a park or the beach and use the app to create the 360º image.

2. Convert the texture to a jpg

If you're converting a hdri, conversion loses the high dynamic range values, so you can use the result as a sky texture, but it is not good for lighting. (hdr files contain rgb values higher than 1.0)

You can convert hdris using Preview, however in an app such as Affinity Photo, you can do tone mapping to bring the high dynamic range into the jpg's low dynamic range.

3. Extract six square textures from the map

Upload the image to: https://jaxry.github.io/panorama-to-cubemap/, convert and download the six cube faces.

Alternatively, to convert on your own computer, go to: https://aerotwist.com/tutorials/create-your-own-environment-maps/ and download from the CONVERT TO CUBE section the Blender file. This Blender file will convert an equirectangular file called environment.jpg. Follow the instructions in that section to create the six images. These will have numbered file names, but the page describes which number equates to which cube face.

4. Import the texture

In your project, create a cube texture in the asset catalog, and drag the six images into their appropriate locations.

Epic Games and rendering in Fortnite

Epic developed an approachable rendering system adapted from Disney's physically based shading algorithms:

Video (bad quality): https://www.youtube.com/watch?v=fJz0GgarVTo
Slides: http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_slides.pdf
Paper: http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf.

This is now widely adopted, and is explained well at:

https://learnopengl.com/PBR/IBL/Diffuse-irradiance

https://learnopengl.com/PBR/IBL/Specular-IBL

Loading hdris

You can download a public domain image loader from: https://github.com/nothings/stb/blob/master/stb_image.h.

GLTFKit from Warren Moore contains Metal code that uses this image loader to load an hdr image image and also has kernels to convolve the result for irradiance maps. https://github.com/warrenm/GLTFKit

You can use cmft to produce radiance and irradiance maps from hdris. Xcode still won't read the results without conversion though. https://github.com/dariomanesku/cmft