harmony 鸿蒙WebGL Overview
WebGL Overview
Web Graphic Library (WebGL) is used for rendering interactive 2D and 3D graphics. WebGL used in OpenHarmony is based on OpenGL for Embedded Systems (OpenGL ES). It can be used in the <canvas> object of HTML5 without using plug-ins and supports cross-platform. WebGL is programmed by JavaScript code. Its APIs can implement graphics rendering and acceleration by using GPU hardware provided by the user equipment. For more information, see WebGL™.
Basic Concepts
Shader
Shaders are instructions and data that run in a graphics card. In WebGL, shaders are written in the OpenGL Shading Language (GLSL).
There are vertex shaders and fragment shaders. The interaction between vertex shaders and fragment shaders involves rasterization.
The vertex shader is mainly used to receive the coordinates of a point in a 3D space, process the coordinates into coordinates in a 2D space, and output the coordinates.
The fragment shader is mainly used to output a color value for each pixel being processed.
Rasterization is the process of converting the coordinates output by the vertex shader into pixels to be processed and passing the pixels to the fragment shader.
Buffer
The buffer is a JavaScript object that resides in memory and stores the attribute object to be pushed to the shader.
WebGLProgram
The WebGLProgram is a JavaScript object responsible for associating the shader with the buffer. A WebGLProgram object consists of two compiled WebGL shaders: a vertex shader and a fragment shader.
Working Principles
Figure 1 WebGL working principles
An application draws UI components using HTML5 at the foreground.
Native APIs complete the interaction between JavaScript and C++ code.
JavaScript engine is the graphics framework that provides the Surface object for the WebGL module.
The WebGL module exposes the GPU drawing APIs of OpenGL ES.
The Embedded Graphics Library (EGL) implements adaptation to different platforms.
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