Noise Functions
This article summarizes the fundamentals of well-known noise functions, for example, Value, Perlin, Simplex noises, and describes how to use them.
- JavaScript 14
- Research 10
- ThreeJS 8
- Conference 6
- WebGL 6
- Journal 3
- Application 2
- Electron 2
- Patent 1
- Dissertation 1
- Python 1
- Mathematics 1
JavaScript
Create a Realistic Sun with Shaders
In the previous article1, we’ve created a realistic Earth. Unlike the Earth that consists of solid elements, the sun is full of gas. In order to render a gas flowing through the surface of the sun, I’ll utilize fractal noise, a.k.a., fractal Brownian motion, that is mentioned at here2. Also, I...
Create a Realistic Earth with Shaders
Let’s return to creating a realistic Earth using Three.js. Unlike the previous Earth1, we are going to render Earth using shader material. First, we will describe the day and night with two different textures, since there are city lights at night. Second, I’ll make an effect for mountain shado...
Shader Design Patterns
Now, it’s time to design a custom pattern to illustrate the shader. Since all vertex and fragment is “blind” to others, we have to script a code with different manner from the concurrent programming. Thus, the position and color of a vertex should be defined with its own attributes and the sha...
Vertex and Fragment
A shader program consists of vertex and fragment shaders. A vertex shader defines the geometric attributes of vertices, whereas fragment shader defines their color. In this post, I’ll address how to create the vertex and fragment shaders and how to use them.
Shader Program
GLSL (OpenGL Shading Language) is a programming language for simple program, Shader, that describes the color attribute of each vertex in parallel computation. Thus, all vertices do not know the status of other vertices nearby, i.e., vertices are blind to the others. But, if we use a uniform v...
Shader Material
A shader material is rendered with a custom shader. It requires vertex and fragment shaders which are written in GLSL (openGL Shading Language) code and depict the position of a vertex and its color, respectively. Since these codes run on the GPU using WebGL, a ShaderMaterial is rendered prope...
PBR (Physical-based rendering) Material
Three.js provides the material attribute for a 3D object, which determines how the object reflects light and how the object is rendered in a camera. The properties of material are composed of base color, metalness, roughness, and so on. Moreover, we can decorate the surface of a 3D object by u...
Scene Graph
Sun-Earth system In this article, I’ll create a simple Sun-Earth system. Firstly, create an orange sphere and a blue sphere which represent the Sun and the Earth, respectively.
How to Create a Scene
Create the scene environment For Three.js to render a scene, it needs scene, camera, and renderer. In JavaScript, you have to import Three.js depending on the installation options as mentioned in the previous article.
Installation
Three.js is a JavaScript library for creating and animating 3D computer graphics in browser using WebGL. 1 https://en.wikipedia.org/wiki/Three.js ↩
How to Create the Solar System
The above image is the snapshot of a solar system simulator.1 The posts will be serialized in the order of contents below. https://portfolio.sangillee.com/apps/solar ↩
How To Publish an Electron App to Github at Build Time
In the page, I’ll introduce a method to build an electron app and automatically publish it to GitHub using electron-builder.
How To Update an Electron App Automatically
The autoUpdater enables an electron app to check the latest version and update itself automatically. 1 https://www.electronjs.org/docs/latest/api/auto-updater ↩
Research
Robust Event-based Angular Velocity Estimation in Dynamic Environments
Abstract: This dissertation addresses the problem of estimating the angular velocity of the event camera with robustness to a dynamic environment where moving objects exist. These vision-based navigation problems have been mainly dealt with in frame-based cameras. The traditional frame-based came...
Low-latency and Scene-robust Optical Flow Stream and Angular Velocity Estimation
Abstract: Event cameras are bio-inspired sensors that capture intensity changes of pixels individually, and generate asynchronous and independent ``events’’. Due to the fundamental difference from the conventional cameras, most research on event cameras builds a global event frame by...
Real-time Object-aware Monocular Depth Estimation in Onboard Systems
Abstract: This paper proposes the object depth estimation in real-time, using only a monocular camera in an onboard computer with a low-cost GPU. Our algorithm estimates scene depth from a sparse feature-based visual odometry algorithm and detects/tracks objects’ bounding box by util...
Robust Real-time RGB-D Visual Odometry in Dynamic Environments via Rigid Motion Model
Abstract: In the paper, we propose a robust real-time visual odometry in dynamic environments via rigid-motion model updated by scene flow. The proposed algorithm consists of spatial motion segmentation and temporal motion tracking. The spatial segmentation first generates several mo...
Edge Detection for Event Cameras using Intra-pixel-area Events
Abstract: In this work, we propose an edge detection algorithm by estimating a lifetime of an event produced from dynamic vision sensor, also known as event camera. The event camera, unlike traditional CMOS camera, generates sparse event data at a pixel whose log-intensity changes. D...
Edge-Based Robust RGB-D Visual Odometry Using 2-D Edge Divergence Minimization
Abstract: This paper proposes an edge-based robust RGB-D visual odometry (VO) using 2-D edge divergence minimization. Our approach focuses on enabling the VO to operate in more general environments subject to low texture and changing brightness, by employing image edge regions and th...
Real-time Rigid Motion Segmentation using Grid-based Optical Flow
Abstract: In the paper, we propose a rigid motion segmentation algorithm with the grid-based optical flow. The algorithm selects several adjacent points among grid-based optical flows to estimate motion hypothesis based on a so-called entropy and generates motion hypotheses between two images, th...
Robust Visual Odometry via Rigid Motion Segmentation for Dynamic Environments
Abstract: In the paper, we propose a robust visual odometry algorithm for dynamic environments via rigid motion segmentation using a grid-based optical flow. The algorithm first divides image frame by a fixed-size grid, then calculates the three-dimensional motion of grids for light ...
Survey on Visual Odometry Technology for Unmanned Systems
Abstract: This paper surveys visual odometry technology for unmanned systems. Visual odometry is one of the most important technologies to implement vision-based navigation; therefore, it is widely applied to unmanned systems in recent years. Visual odometry estimates a trajectory and a pose of t...
Exposure Correction and Image Blending for Planar Panorama Stitching
Abstract: In this paper, we propose a planar panorama stitching method to blend consecutive images captured by a multirotor equipped with a fish-eye camera. In addition, we suggest an exposure correction method to reduce the brightness difference between contiguous images, and a drift error corre...
ThreeJS
Create a Realistic Sun with Shaders
In the previous article1, we’ve created a realistic Earth. Unlike the Earth that consists of solid elements, the sun is full of gas. In order to render a gas flowing through the surface of the sun, I’ll utilize fractal noise, a.k.a., fractal Brownian motion, that is mentioned at here2. Also, I...
Create a Realistic Earth with Shaders
Let’s return to creating a realistic Earth using Three.js. Unlike the previous Earth1, we are going to render Earth using shader material. First, we will describe the day and night with two different textures, since there are city lights at night. Second, I’ll make an effect for mountain shado...
Shader Material
A shader material is rendered with a custom shader. It requires vertex and fragment shaders which are written in GLSL (openGL Shading Language) code and depict the position of a vertex and its color, respectively. Since these codes run on the GPU using WebGL, a ShaderMaterial is rendered prope...
PBR (Physical-based rendering) Material
Three.js provides the material attribute for a 3D object, which determines how the object reflects light and how the object is rendered in a camera. The properties of material are composed of base color, metalness, roughness, and so on. Moreover, we can decorate the surface of a 3D object by u...
Scene Graph
Sun-Earth system In this article, I’ll create a simple Sun-Earth system. Firstly, create an orange sphere and a blue sphere which represent the Sun and the Earth, respectively.
How to Create a Scene
Create the scene environment For Three.js to render a scene, it needs scene, camera, and renderer. In JavaScript, you have to import Three.js depending on the installation options as mentioned in the previous article.
Installation
Three.js is a JavaScript library for creating and animating 3D computer graphics in browser using WebGL. 1 https://en.wikipedia.org/wiki/Three.js ↩
How to Create the Solar System
The above image is the snapshot of a solar system simulator.1 The posts will be serialized in the order of contents below. https://portfolio.sangillee.com/apps/solar ↩
Conference
Robust Real-time RGB-D Visual Odometry in Dynamic Environments via Rigid Motion Model
Abstract: In the paper, we propose a robust real-time visual odometry in dynamic environments via rigid-motion model updated by scene flow. The proposed algorithm consists of spatial motion segmentation and temporal motion tracking. The spatial segmentation first generates several mo...
Edge Detection for Event Cameras using Intra-pixel-area Events
Abstract: In this work, we propose an edge detection algorithm by estimating a lifetime of an event produced from dynamic vision sensor, also known as event camera. The event camera, unlike traditional CMOS camera, generates sparse event data at a pixel whose log-intensity changes. D...
Edge-Based Robust RGB-D Visual Odometry Using 2-D Edge Divergence Minimization
Abstract: This paper proposes an edge-based robust RGB-D visual odometry (VO) using 2-D edge divergence minimization. Our approach focuses on enabling the VO to operate in more general environments subject to low texture and changing brightness, by employing image edge regions and th...
Real-time Rigid Motion Segmentation using Grid-based Optical Flow
Abstract: In the paper, we propose a rigid motion segmentation algorithm with the grid-based optical flow. The algorithm selects several adjacent points among grid-based optical flows to estimate motion hypothesis based on a so-called entropy and generates motion hypotheses between two images, th...
Robust Visual Odometry via Rigid Motion Segmentation for Dynamic Environments
Abstract: In the paper, we propose a robust visual odometry algorithm for dynamic environments via rigid motion segmentation using a grid-based optical flow. The algorithm first divides image frame by a fixed-size grid, then calculates the three-dimensional motion of grids for light ...
Exposure Correction and Image Blending for Planar Panorama Stitching
Abstract: In this paper, we propose a planar panorama stitching method to blend consecutive images captured by a multirotor equipped with a fish-eye camera. In addition, we suggest an exposure correction method to reduce the brightness difference between contiguous images, and a drift error corre...
WebGL
Noise Functions
This article summarizes the fundamentals of well-known noise functions, for example, Value, Perlin, Simplex noises, and describes how to use them.
Create a Realistic Sun with Shaders
In the previous article1, we’ve created a realistic Earth. Unlike the Earth that consists of solid elements, the sun is full of gas. In order to render a gas flowing through the surface of the sun, I’ll utilize fractal noise, a.k.a., fractal Brownian motion, that is mentioned at here2. Also, I...
Create a Realistic Earth with Shaders
Let’s return to creating a realistic Earth using Three.js. Unlike the previous Earth1, we are going to render Earth using shader material. First, we will describe the day and night with two different textures, since there are city lights at night. Second, I’ll make an effect for mountain shado...
Shader Design Patterns
Now, it’s time to design a custom pattern to illustrate the shader. Since all vertex and fragment is “blind” to others, we have to script a code with different manner from the concurrent programming. Thus, the position and color of a vertex should be defined with its own attributes and the sha...
Vertex and Fragment
A shader program consists of vertex and fragment shaders. A vertex shader defines the geometric attributes of vertices, whereas fragment shader defines their color. In this post, I’ll address how to create the vertex and fragment shaders and how to use them.
Shader Program
GLSL (OpenGL Shading Language) is a programming language for simple program, Shader, that describes the color attribute of each vertex in parallel computation. Thus, all vertices do not know the status of other vertices nearby, i.e., vertices are blind to the others. But, if we use a uniform v...
Journal
Low-latency and Scene-robust Optical Flow Stream and Angular Velocity Estimation
Abstract: Event cameras are bio-inspired sensors that capture intensity changes of pixels individually, and generate asynchronous and independent ``events’’. Due to the fundamental difference from the conventional cameras, most research on event cameras builds a global event frame by...
Real-time Object-aware Monocular Depth Estimation in Onboard Systems
Abstract: This paper proposes the object depth estimation in real-time, using only a monocular camera in an onboard computer with a low-cost GPU. Our algorithm estimates scene depth from a sparse feature-based visual odometry algorithm and detects/tracks objects’ bounding box by util...
Survey on Visual Odometry Technology for Unmanned Systems
Abstract: This paper surveys visual odometry technology for unmanned systems. Visual odometry is one of the most important technologies to implement vision-based navigation; therefore, it is widely applied to unmanned systems in recent years. Visual odometry estimates a trajectory and a pose of t...
Application
Solla Solar
Solla Solar is a simple 2D solar system simulator. By manipulating the screen, you can observe the past, present, and future of the solar system.
Gravity Simulator
This is an application to simulate particles’ movement under Newton’s law of universal gravitation. Particles attract each other, and then they are collided and merged or orbit the center of mass. Some particles can fade away toward the horizon of the universe. I designed and implemented the appl...
Electron
How To Publish an Electron App to Github at Build Time
In the page, I’ll introduce a method to build an electron app and automatically publish it to GitHub using electron-builder.
How To Update an Electron App Automatically
The autoUpdater enables an electron app to check the latest version and update itself automatically. 1 https://www.electronjs.org/docs/latest/api/auto-updater ↩
Patent
Ego Motion Estimation Method and Apparatus
Abstract: Disclosed is an ego motion estimation method and apparatus, wherein the apparatus calculates a scene flow field from a plurality of spaces of an input image, clusters the plurality of spaces based on a scene flow, updates a probability vector map for clustered spaces, identifies a stati...
Dissertation
Robust Event-based Angular Velocity Estimation in Dynamic Environments
Abstract: This dissertation addresses the problem of estimating the angular velocity of the event camera with robustness to a dynamic environment where moving objects exist. These vision-based navigation problems have been mainly dealt with in frame-based cameras. The traditional frame-based came...
Python
How to Compute Faster 2-D Convolution in Python
In image processing, 2-D convolution is a highly useful operation. It can be used for tasks such as blurring, morphology, edge detection, and sharpening. In Python, a naive 2-D convolution method takes a huge computational load for a large image. This post introduces the use of np.lib.stride_t...
Mathematics
A Derivation of Depth Filter
The depth filter is a useful component in monocular camera visual odometry systems, such as SVO (Semi-Direct Visual Odometry) 1 2. It is designed to estimate depth values from a sequence of images captured by a single camera. The filter operates under the assumption of Gaussian measurement noi...