OpenGL ES 2.0 API速查卡片
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"OpenGL ES 2.0 是一个针对嵌入式系统的图形库，用于在硬件上绘制高质量的三维图像。这个接口由一系列程序和函数组成，允许程序员定义创建高质量图形图像所需的对象和操作，尤其是三维度的颜色图像。OpenGL ES 2.0 参考卡提供了快速查阅的API信息，包括顶点、顶点数组和缓冲对象等关键概念。"
OpenGL ES 2.0 API 是一个针对移动设备和嵌入式系统设计的轻量级图形库，它是桌面版 OpenGL 的子集，专为低功耗设备优化。该版本引入了着色器模型，显著增强了图形处理能力，使得开发者能够编写更复杂的图形渲染算法。
1. **顶点状态与顶点属性**：
- `VertexAttrib{1234}{f}` 和 `VertexAttrib{1234}{f}v` 函数用于设置顶点属性，如位置、颜色、纹理坐标等。`index` 参数指定了要修改的顶点属性索引，`Tvalues` 是值的类型，可以是浮点或整数。
2. **顶点数组**：
- `VertexAttribPointer` 函数定义了顶点数据如何从应用内存或GPU内存（通过缓冲对象）获取。`size` 指定每项的组件数量，`type` 定义了数据类型，`normalized` 表示是否将整数数据归一化，`stride` 为相邻顶点之间的字节偏移量，`pointer` 是数据的指针。
- 支持的数据类型包括：BYTE, UNSIGNED_BYTE, SHORT, UNSIGNED_SHORT, FIXED, FLOAT。顶点属性索引 `index` 不能超过 `MAX_VERTEX_ATTRIBS-1`，这是系统定义的最大顶点属性数。
3. **缓冲对象**：
- 在OpenGL ES 2.0中，缓冲对象用于存储顶点数据，以提高数据传输效率和减少CPU参与度。通过`glBindBuffer`绑定缓冲区，然后使用`VertexAttribPointer`指定顶点数组的来源。
4. **着色语言**：
- OpenGL ES Shading Language (GLSL ES) 1.0 规范中的 `[n.n.n]` 引用对应章节，用于编写顶点和片段着色器。着色器允许开发者自定义图形管线中的计算步骤，实现高级渲染效果。
5. **图形管线**：
- OpenGL ES 2.0 中的图形管线包括顶点处理（如位置变换、光照计算）、几何处理（裁剪、视口转换）和像素处理（颜色混合、深度测试）等阶段。开发者可以通过编写着色器控制管线的各个部分。
6. **状态管理**：
- OpenGL ES 2.0 提供了一系列函数来管理状态，如启用或禁用特定特性（如深度测试、混合），设置矩阵栈，以及控制顶点数组和纹理的参数。
OpenGL ES 2.0 参考卡是开发者理解和使用这个API的关键工具，它包含了从基本的顶点操作到复杂的着色器编程的全面信息，是开发图形密集型应用时不可或缺的参考资料。更多详细信息，可以在Khronos Group的官方网站上找到OpenGL ES 2.0和GLSL ES 1.0的完整规范。
www.khronos.org/opengles©2010 Khronos Group - Rev. 0210
OpenGL ES 2.0 API Quick Reference Card
OpenGL
®
ES is a soware interface to graphics hardware. The interface
consists of a set of procedures and funcons that allow a programmer to specify
the objects and operaons involved in producing high-quality graphical images,
specically color images of three-dimensional objects.
• [n.n.n] refers to secons and tables in the OpenGL ES 2.0 specicaon.
• [n.n.n] refers to secons in the OpenGL ES Shading Language 1.0
specicaon.
Specicaons are available at www.opengl.org/registry/gles
Verces
Current Vertex State [2.7]
void VertexArib{1234}{f}(uint index, T values);
void VertexArib{1234}{f}v(uint index, T values);
Vertex Arrays [2.8]
Vertex data may be sourced from arrays that are stored in applicaon
memory (via a pointer) or faster GPU memory (in a buer object).
void VertexAribPointer(uint index, int size, enum type,
boolean normalized, sizei stride, const void *pointer);
type: BYTE, UNSIGNED_BYTE, SHORT, UNSIGNED_SHORT, FIXED, FLOAT
index: [0, MAX_VERTEX_ATTRIBS - 1]
If an ARRAY_BUFFER is bound, the aribute will be read from the
bound buer, and pointer is treated as an oset within the buer.
void EnableVertexAribArray(uint index);
void DisableVertexAribArray(uint index);
index: [0, MAX_VERTEX_ATTRIBS - 1]
void DrawArrays(enum mode, int rst, sizei count);
void DrawElements(enum mode, sizei count, enum type,
void *indices);
mode: POINTS, LINE_STRIP, LINE_LOOP, LINES, TRIANGLE_STRIP,
TRIANGLE_FAN, TRIANGLES
type: UNSIGNED_BYTE, UNSIGNED_SHORT
If an ELEMENT_ARRAY_BUFFER is bound, the indices will be read
from the bound buer, and indices is treated as an oset within
the buer.
OpenGL ES Command Syntax [2.3]
Open GL ES commands are formed from a return type, a name, and oponally a type leer i for 32-bit int, or f for 32-bit oat,
as shown by the prototype below:
return-type Name{1234}{if}{v} ([args ,] T arg1 , . . . , T argN [, args]);
The arguments enclosed in brackets ([args ,] and [, args]) may or may not be present.
The argument type T and the number N of arguments may be indicated by the command name suxes. N is 1, 2, 3, or 4 if
present, or else corresponds to the type leers. If “v” is present, an array of N items is passed by a pointer.
For brevity, the OpenGL documentaon and this reference may omit the standard prexes.
The actual names are of the forms: glFunconName(), GL_CONSTANT, GLtype
Errors [2.5]
enum GetError( void );
//Returns one of the following:
INVALID_ENUM Enum argument out of range
INVALID_FRAMEBUFFER_OPERATION Framebuer is incomplete
INVALID_VALUE Numeric argument out of range
INVALID_OPERATION Operaon illegal in current state
OUT_OF_MEMORY Not enough memory le to execute command
NO_ERROR No error encountered
Buer Objects
[2.9]
Buer objects hold vertex array data or indices in
high-performance server memory.
void GenBuers(sizei n, uint *buers);
void DeleteBuers(sizei n, const uint *buers);
Creang and Binding Buer Objects
void BindBuer(enum target, uint buer);
target: ARRAY_BUFFER, ELEMENT_ARRAY_BUFFER
Creang Buer Object Data Stores
void BuerData(enum target, sizeiptr size,
const void *data, enum usage);
usage: STATIC_DRAW, STREAM_DRAW, DYNAMIC_DRAW
Updang Buer Object Data Stores
void BuerSubData(enum target, intptr oset,
sizeiptr size, const void *data);
target: ARRAY_BUFFER, ELEMENT_ARRAY_BUFFER
Buer Object Queries [6.1.6, 6.1.3]
boolean IsBuer(uint buer);
void GetBuerParameteriv(enum target, enum value,
T data);
target: ARRAY_BUFFER, ELEMENT_ ARRAY_BUFFER
value: BUFFER_SIZE, BUFFER_USAGE
Viewport and Clipping
Controlling the Viewport
[2.12.1]
void DepthRangef(clampf n, clampf f);
void Viewport(int x, int y, sizei w, sizei h);
Rasterizaon [3]
Points [3.3]
Point size is taken from the shader builn gl_PointSize and
clamped to the implementaon-dependent point size range.
Line Segments [3.4]
void LineWidth(oat width);
Polygons [3.5]
void FrontFace(enum dir);
dir: CCW, CW
void CullFace(enum mode);
mode: FRONT, BACK, FRONT_AND_BACK
Enable/Disable(CULL_FACE)
void PolygonOset(oat factor, oat units);
Enable/Disable(POLYGON_OFFSET_FILL)
Pixel Rectangles [3.6, 4.3]
void PixelStorei(enum pname, int param);
pname: UNPACK_ALIGNMENT, PACK_ALIGNMENT
Texturing [3.7]
Shaders support texturing using at least
MAX_VERTEX_TEXTURE_IMAGE_UNITS images for vertex
shaders and at least MAX_TEXTURE_IMAGE_UNITS images
for fragment shaders.
void AcveTexture(enum texture);
texture: [TEXTURE0..TEXTUREi] where i =
MAX_COMBINED_TEXTURE_IMAGE_UNITS-1
Texture Image Specicaon [3.7.1]
void TexImage2D(enum target, int level, int internalformat,
sizei width, sizei height, int border, enum format,
enum type, void *data);
target: TEXTURE_2D, TEXTURE_CUBE_MAP_POSITIVE_{X,Y,Z}
TEXTURE_CUBE_MAP_NEGATIVE_{X,Y,Z}
internalformat: ALPHA, LUMINANCE, LUMINANCE_ALPHA, RGB,
RGBA
format: ALPHA, RGB, RGBA, LUMINANCE, LUMINANCE_ALPHA
type: UNSIGNED_BYTE, UNSIGNED_SHORT_5_6_5,
UNSIGNED_SHORT_4_4_4_4, UNSIGNED_SHORT_5_5_5_1
Conversion from RGBA pixel components to internal
texture components:
Base Internal Format
RGBA
Internal Components
ALPHA
A
A
LUMINANCE
R L
LUMINANCE _ALPHA R, A L, A
RGB R, G, B R, G, B
RGBA
R, G, B, A R, G, B, A
Alt. Texture Image Specicaon Commands [3.7.2]
Texture images may also be specied using image data taken
directly from the framebuer, and rectangular subregions of
exisng texture images may be respecied.
void CopyTexImage2D(enum target, int level,
enum internalformat, int x, int y, sizei width,
sizei height, int border);
target: TEXTURE_2D, TEXTURE_CUBE_MAP_POSITIVE_{X, Y, Z},
TEXTURE_CUBE_MAP_NEGATIVE_{X, Y, Z}
internalformat: See TexImage2D
void TexSubImage2D(enum target, int level, int xoset,
int yoset, sizei width, sizei height, enum format,
enum type, void *data);
target: TEXTURE_CUBE_MAP_POSITIVE_{X, Y, Z},
TEXTURE_CUBE_MAP_NEGATIVE_{X, Y, Z}
format and type: See TexImage2D
void CopyTexSubImage2D(enum target, int level, int xoset,
int yoset, int x, int y, sizei width, sizei height);
target: TEXTURE_2D, TEXTURE_CUBE_MAP_POSITIVE_{X, Y, Z},
TEXTURE_CUBE_MAP_NEGATIVE_{X, Y, Z}
format and type: See TexImage2D
Compressed Texture Images [3.7.3]
void CompressedTexImage2D(enum target, int level,
enum internalformat, sizei width, sizei height,
int border, sizei imageSize, void *data);
target and internalformat: See TexImage2D
void CompressedTexSubImage2D(enum target, int level,
int xoset, int yoset, sizei width, sizei height,
enum format, sizei imageSize, void *data);
target and internalformat: See TexImage2D
Texture Parameters [3.7.4]
void TexParameter{if}(enum target, enum pname,
T param);
void TexParameter{if}v(enum target, enum pname,
T params);
target: TEXTURE_2D, TEXTURE_CUBE_MAP
pname: TEXTURE_WRAP_{S, T}, TEXTURE_{MIN, MAG}_FILTER
Manual Mipmap Generaon [3.7.11]
void GenerateMipmap(enum target);
target: TEXTURE_2D, TEXTURE_CUBE_MAP
Texture Objects [3.7.13]
void BindTexture(enum target, uint texture);
void DeleteTextures(sizei n, uint *textures);
void GenTextures(sizei n, uint *textures);
Enumerated Queries [6.1.3]
void GetTexParameter{if}v(enum target, enum value,
T data);
target: TEXTURE_2D, TEXTURE_CUBE_MAP
value: TEXTURE_WRAP_{S, T}, TEXTURE_{MIN, MAG}_FILTER
Texture Queries [6.1.4]
boolean IsTexture(uint texture);
GL Data Types [2.3]
GL types are not C types.
GL Type
Minimum
Bit Width Descripon
boolean 1 Boolean
byte 8 Signed binary integer
ubyte 8 Unsigned binary integer
char 8 Characters making up strings
short 16 Signed 2’s complement binary integer
ushort 16 Unsigned binary integer
int 32 Signed 2’s complement binary integer
uint 32 Unsigned binary integer
xed 32 Signed 2’s complement 16.16 scaled integer
sizei 32 Non-negave binary integer size
enum 32 Enumerated binary integer value
intptr ptrbits Signed 2’s complement binary integer
sizeiptr ptrbits Non-negave binary integer size
biield 32 Bit eld
oat 32 Floang-point value
clampf 32 Floang-point value clamped to [0; 1]
Reading Pixels
[4.3.1]
void ReadPixels(int x, int y, sizei width, sizei height,
enum format, enum type, void *data);
format: RGBA type: UNSIGNED_BYTE
Note: ReadPixels() also accepts a queriable implementaon-
dened format/type combinaon, see [4.3.1]
.
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