• Interactive Poisson Blending on GPU
• Simplest and Fastest GLSL Edge Detection using Fwidth

# Category: Code

### PostProcessing: Brightness, Contrast, Hue, Saturation, and Vibrance

Real-time image manipulation is always fascinating. With the power of the modern GPU, it is possible to achieve the postprocessing effects all in a single shader. Remember that in GLSL, matrix are column major. Brightness is a float between [-1, 1], directly adding to the RGB Contrast is a float between [0, 1, ∞], directly…

### [Leetcode] 691. Stickers to Spell Word

Leetcode 691 is an interesting problem, I didn’t notice that T <= 15. BFS is good enough (and even faster) for this, but dynamic programming with bit compression is the ultimate solution with more words.

### Code Golf: Halftone Image

This is a code golf with the help of Dr. Neyret and coyote. Demo   Code

### Dotted Drawing / Sketch Effect

After lunch, I want to replicate the sketch shader I wrote for the Pencil-vs-Camera project. Additionally, I wrote a one-pass shader for dotted drawing / sketch post processing effect, which I think is more aesthetically pleasing. Dotted Drawing Demo Click on the play button in the left bottom corner of the embedded ShaderToy window below, to…

### Unified Gnomonic and Stereographic Projections

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…

### 0-4 Order of Spherical Harmonics

Spherical Harmonics is widely used in Computer Graphics. They are analogue to Fourier basis on a sphere, consists of a set of orthogonal functions to represent functions defined on the surface of a sphere. However, they are very tricky to implement due to lots of constants and integral functions. Here is a real-time visualization that…

Taken iq’s background transparent code and Dr. Neyret’s advice: This shader can be used for rendering pop-up images in a 3D environment.