Gnomonic projection, or rectilinear projection, together with stereographic projection, are two most commonly used projection in rendering 360 degree videos, or other VR applications. Recently, I found the inverse converting function from screen coordinates to the two projections can be unified within a single function. It’s not really surprising since both projection uses spherical lens,…
Equirectangular, Gnomonic Projections, and Cubemaps
Background According to MathWorld, the gnomonic projection is a nonconformal map projection obtained by projecting points P_1 (or P_2) on the surface of sphere from a sphere’s center O to point P in a plane that is tangent to a point S (Coxeter 1969, p. 93). In a gnomonic projection, great circles are mapped to…
SIGGRAPH Asia 2014 Course Materials from iq/rgba
iñigo quilez kindly provides his SIGGRAPH Asia 2014 Course Materials of ShaderToy with me via email. Thank you iq! Thinking implicit: 2D, non polygonal shapes Coordinates and color gradients (That link is depracated, so I personally recommend this link instead) Shapping Texture Mapping Animation Reactivity More Media Yet More Media Thinking implicit: 3D Raymarching Modeling (primitives and…
Tutorial and Resources for Three.js
Three.js is one of a number of free WebGL libraries. First released in April 2010, it has become pretty popular, and includes a huge number of demos. I wanted to know more about its origins, so interviewed its creator, Ricardo Cabello, aka mr.doob, who lives in Spain. Interestingly, I am also largely motivated by Demoscenes when I was…
Tutorial of Ray Casting, Ray Tracing and Ray Marching
Introduction As GPU power is becoming significantly better than CPU, ray casting / tracing and ray marching is widely used in 4k intros and demoscenes to create 3D (interactive) graphics. – Thanks to all the references listed in the end, I learnt so much about and I would like to share with the knowledge to my friends. This tutorial…
Quick Tutorial on Refereces Management using Mendeley / Endnote / Word / ShareLaTeX
Managing a large library of references for researchers can be hard work. I usually use Mendeley + ShareLaTeX for writing papers. Both tools are free and easy to collaborate with co-authors. Mendeley + ShareLaTeX First, please install Mendeley from its official website. Here is an official YouTube video introducing Mendeley: There is also a quick…
[Tutorial] Introduction and Installation of WebVR
Today I tried a new technology called WebVR. According to WebVR.info: WebVR is an experimental Javascript API that provides access to Virtual Reality devices, such as the Oculus Rift or Google Cardboard, in your browser. It tries to provide a uniform interface for all sorts of VR headsets such as Oculus Rift DK2, Google Cardboard…
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