Android OpenGL ES (i)

Ext.: http://wiki.jikexueyuan.com/project/opengl-es-guide/pipeline.html

OpenGL ES is primarily used to develop 3D graphics applications. OpenGL ES (OpenGL for Embedded Systems) is a subset of the OpenGL three-dimensional graphics API, designed for embedded devices such as mobile phones, PDAs, and game consoles.

What is OpenGL ES?

• OpenGL ES (abbreviated for the OpenGL for Embedded system) is a free two-and three-dimensional graphics library for embedded systems.
• A subset of the desktop version of OpenGL.
• OpenGL ES defines a streamlined standard on a mobile platform that supports OpenGL's most basic functionality to accommodate display systems such as mobile phones, PDAs, or other consumer mobile terminals.
• The Khronos Group defines and manages the OpenGL ES standard.

The relationship between OpenGL and OpenGL ES

OpenGL ES is based on the desktop version of OpenGL, showing the diagram between OpenGL and OpenGL ES

• OpenGL ES 1.0 based on OpenGL 1.3, released in 2003
• OpenGL ES 1.1 based on OpenGL 1.5, released in 2004
• OpenGL ES 2.0 based on OpenGL2.0, released in 2007
• OpenGL 2.0 is backwards compatible with OpenGL 1.5 and OpenGL ES 2.0 and OpenGL ES 1.x are incompatible, and are two completely different implementations.

OpenGL ES Pipeline (Pipeline)

Most graphics systems can be likened to assembly lines (Assemble line) or pipes (Pipeline) in a factory. The previous output is the input for the next operation. The main CPU emits a drawing instruction, which can then be transformed by a hardware part, trimmed, added with color or material, and then displayed on the screen.

The process of OpenGL ES 1.x is fixed, called Fix-function Pipeline, and you can imagine a machine with a lot of control switches, even though the process is fixed, but you can set parameters by turning the switch on or off, or turn off certain functions.

OpenGL ES 2.0 allows for programming to control important processes, and some "tedious" processes such as rasterization are still fixed.

Shows the structure of the OpenGL ES 1.x fixed pipe:

• Pipeline "Operation" can be divided into transformation stage and rasterization stage two major strides.
• The basic graphics supported by OpenGL ES are point points, line lines, and Triangle Triangle, and all other copied graphics are combined by these basic geometries.
• After the drawing instruction is issued, the vertex (Vertices) array is assigned a coordinate transformation or light processing.
• When vertex processing is complete, pixel information is generated by Rasterizer, called "Fragments".
• For Fragment after Texture processing, Color Sum, Fog, and so on are processed and the final processing results are stored in memory (called framebuffer).
• OpenGL 2.0 can be programmed to modify the blue steps, called Programmable Shader.

The operations in the above pipeline can be set to turn certain functions on or off (such as no atomization Fog processing) and can set parameters for an operation, such as setting the Vertext Array.

(EXT) Android OpenGL ES (i)