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。

OpenGL ES 2.0 API Quick Reference Card

OpenGL

ES is a soware interface to graphics hardware. The interface

consists of a set of procedures and funcons that allow a programmer to specify

the objects and operaons involved in producing high-quality graphical images,

specically color images of three-dimensional objects.

• [n.n.n] refers to secons and tables in the OpenGL ES 2.0 specicaon.

• [n.n.n] refers to secons in the OpenGL ES Shading Language 1.0

specicaon.

Specicaons are available at www.opengl.org/registry/gles

Verces

Current Vertex State [2.7]

void VertexArib{1234}{f}(uint index, T values);

void VertexArib{1234}{f}v(uint index, T values);

Vertex Arrays [2.8]

Vertex data may be sourced from arrays that are stored in applicaon

memory (via a pointer) or faster GPU memory (in a buer object).

void VertexAribPointer(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 aribute will be read from the

bound buer, and pointer is treated as an oset within the buer.

void EnableVertexAribArray(uint index);

void DisableVertexAribArray(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 buer, and indices is treated as an oset within

the buer.

OpenGL ES Command Syntax [2.3]

Open GL ES commands are formed from a return type, a name, and oponally a type leer 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 suxes. N is 1, 2, 3, or 4 if

present, or else corresponds to the type leers. If “v” is present, an array of N items is passed by a pointer.

For brevity, the OpenGL documentaon and this reference may omit the standard prexes.

The actual names are of the forms: glFunconName(), GL_CONSTANT, GLtype

Errors [2.5]

enum GetError( void );

//Returns one of the following:

INVALID_ENUM Enum argument out of range

INVALID_FRAMEBUFFER_OPERATION Framebuer is incomplete

INVALID_VALUE Numeric argument out of range

INVALID_OPERATION Operaon illegal in current state

OUT_OF_MEMORY Not enough memory le to execute command

NO_ERROR No error encountered

Buer Objects

[2.9]

Buer objects hold vertex array data or indices in

high-performance server memory.

void GenBuers(sizei n, uint *buers);

void DeleteBuers(sizei n, const uint *buers);

Creang and Binding Buer Objects

void BindBuer(enum target, uint buer);

target: ARRAY_BUFFER, ELEMENT_ARRAY_BUFFER

Creang Buer Object Data Stores

void BuerData(enum target, sizeiptr size,

const void *data, enum usage);

usage: STATIC_DRAW, STREAM_DRAW, DYNAMIC_DRAW

Updang Buer Object Data Stores

void BuerSubData(enum target, intptr oset,

sizeiptr size, const void *data);

target: ARRAY_BUFFER, ELEMENT_ARRAY_BUFFER

Buer Object Queries [6.1.6, 6.1.3]

boolean IsBuer(uint buer);

void GetBuerParameteriv(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);

Rasterizaon [3]

Points [3.3]

Point size is taken from the shader builn gl_PointSize and

clamped to the implementaon-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 PolygonOset(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 AcveTexture(enum texture);

texture: [TEXTURE0..TEXTUREi] where i =

MAX_COMBINED_TEXTURE_IMAGE_UNITS-1

Texture Image Specicaon [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

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 Specicaon Commands [3.7.2]

Texture images may also be specied using image data taken

directly from the framebuer, and rectangular subregions of

exisng texture images may be respecied.

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 xoset,

int yoset, 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 xoset,

int yoset, 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 xoset, int yoset, 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 Generaon [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 Descripon

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-negave binary integer size

enum 32 Enumerated binary integer value

intptr ptrbits Signed 2’s complement binary integer

sizeiptr ptrbits Non-negave binary integer size

biield 32 Bit eld

oat 32 Floang-point value

clampf 32 Floang-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 implementaon-

dened format/type combinaon, see [4.3.1]

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