OpenGL學習筆記-2015.4.1——紋理載入與控制
阿新 • • 發佈：2019-01-22
在紋理貼圖技術問世之前，虛擬3維世界只能通過幾何模型去模擬現實，可想而知，現實世界的錯綜複雜，計算量之大並不能滿足實時顯示的需求。紋理對映帶來了革命性的變換，簡單的使得虛擬的3維世界得以無限接近於現實。紋理對映技術最早是由Catmull 在1947年率先提出的，Catmull首先找到了以（u,v）表示的雙變數實數空間(紋理空間)和以引數(s,t)表示的三維曲面之間的對應關係(對映關係)。
紋理由紋素組成，通常包括顏色值。但是在實際應用中，很多時候把紋理看作可以再著色器中查詢的表（一個儲存資料的地方），你可以用於任何目的，不僅僅侷限於紋理貼圖。
基本紋理型別：
OpenGL支援多型別的維數和佈局可變的紋理物件，每個紋理物件表示組成完整紋理的一組影象，可以是1維，2維，3維陣列。紋理可以使用用於2維和2維陣列紋理的多重取樣的紋理型別來表示多重取樣顏色。多重取樣是一個用於抗鋸齒的術語，其中每個紋素被賦予多個獨立的顏色，然後在渲染過程中合併這些顏色來生成最終的顏色。
紋理通過紋理單元繫結到OpenGL中，紋理單元命名為GL_TEXTURE0到GL_TEXTUREi(i是OpenGL實現所支援的最大紋理數目減一)的繫結點。只要一個紋理繫結到環境中，則在著色器中可以使用取樣器來訪問，而取樣器變數用匹配紋理的維數來宣告，具體看下錶：
ps:很多型別的紋理對映現在自己並沒用用到對於一些概念還是比較模糊，在此mark~~什麼時候瞭解了回來改改
一些特殊的紋理物件：1、矩形紋理物件（GL_TEXTURE_RECTANGLE）,2維紋理的特例，表示一個簡單的矩陣，沒用mipmap(層次紋理)並且不能表示為紋理陣列？！一些紋理模式（texture wrapping）不支援矩陣紋理。2、緩衝紋理（GL_TEXTURE_BUFFER）,表示紋素的1維陣列。同樣沒有mipmap,不能聚合陣列。紋理緩衝是任意著色器階段的資料訪問（頂點資料，顏色。。。）而不需要把資料拷貝到紋理影象中。
紋理對映四步曲：
具體意義課查閱openGL文件：https://www.opengl.org/sdk/docs/man4/ ctrl+f函式名稱即可。有詳細的解釋。
當沒有采樣器物件繫結到對應的取樣器單元時，每個用來從紋理中讀取資料的紋理物件都有預設的取樣器物件。為了修改這些引數，可以使用glTexParameter*()函式。
void glTexParameter{fi}( GLenum target, GLenum pname, Type param )
void glTexParameter{fi}v( GLenum target, GLenum pname, Type, param )
void glTexParameterl{fi}v( GLenum target, GLenum pname, Type param )
target引數表示繫結到當前啟用紋理單元的紋理物件，pname ,與 param大致與glSamplerParameter*()相同，不過glTexParameter*()有更多不同的引數，控制不同方面的內容，如當還有對於外部的資料來源，並不能保證其紋理資料的儲存順序均為RGBA分分量順序。所以OpenGL提供了在讀取時紋理資料的儲存順序設定。man手冊萬能：https://www.opengl.org/sdk/docs/man4/
最後你是刪除sampler物件的介面：glDeleteSamplers( GLsizei count, const GLuint* samplers )
GLSL在著色器階段可以使用內建函式來讀取紋理資訊。texture()的幾個過載版本。
Gvec4 texture( gsampler1D tex, float P[, float bias] )
Gvec4 texture( gsampler2D tex, float P[, float bias] );
Gvec4 texture( gsampler3D tex, float P[, float bias] );
Gvec4 texture( gsamplerCube tex, float P[, float bias] );
Gvec4 texture( gsampler1DArray tex, float P[, float bias] );
Gvec4 texture( gsampler2DArray tex, float P[, float bias] );
Gvec4 texture( gsampler2DRect tex, float P[, float bias] );
Gvec4 texture( gsamplerCubeArray tex, float P[, float bias] );
tex表示紋理取樣器型別，前面加g相當於一個佔位符，如gsampler2D可以表示sampler2D, isampler2D,或則usampler2D.Gvec4也是可以表示vec4 ivec4 uvec4.。p表示紋理的紋理座標，bias表示如果啟動了mipmapping,用來偏移確定mipmap的細節層次計算。
4、幾個簡單的例子，程式碼中對於使用到的一些介面引數會有詳細的解釋。
先來看一下LoadTexture的內容。
b、紋理座標越界控制
GL_CLAMP_TO_EDGE模式
GL_CLAMP_TO_BORDER模式
GL_REPEAT模式
GL_MIRROED_REPEAT模式。
c、使用多重紋理。
The End~~
希望堅持和努力會迎來好的結果。
| 目標GL_TEXTURE* | 取樣器型別 | 維度 |
| 1D | sampler1D | 1D |
| 1D_ARRAY | sampler1DArray | 1D陣列 |
| 2D | sampler2D | 2D |
| 2D_ARRAY | sampler2DArray | 2D陣列 |
| 2D_MULTISAMPLE | sampler2DMS | 2D多重取樣 |
| 2D_MULTISAMPLE_ARRAY | sampler2DMSArray | 2D多重取樣陣列 |
| 3D | sampler3D | 3D |
| CUBE | samplerCube | 立方體紋理對映 |
| ARRAY | samplerCubeArray | 立方體對映陣列 |
| RECTANGLE | samplerRect | 2D矩陣 |
| BUFFER | samplerBuffer | 1D快取 |
| pname | param |
| GL_TEXTURE_MAG_FILTER | GL_NEAREST、GL_LINEAR |
| GL_TEXTURE_MIN_FILTER | GL_NEAREST、GL_LINEAR、GL_NEAREST_MIPMAP_NEAREST、GL_NEAREST_MIPMAP_LINEAR、GL_LINEAR_MIPMAP_NEAREST、GL_LINEAR_MIPMAP_LINEAR |
| GL_TEXTURE_WRAP_S、GL_TEXTURE_WRAP_T | GL_REPEAT、GL_CLAMP_TO_EDGE、GL_MIRRORED_REPEAT |
GLuint vglLoadTexture(const char* filename,
GLuint texture,
vglImageData* image)
{
vglImageData local_image;
int level;
if (image == 0)
image = &local_image;
vglLoadImage(filename, image);
if (texture == 0)
{
glGenTextures(1, &texture);
}
glBindTexture(image->target, texture);
GLubyte * ptr = (GLubyte *)image->mip[0].data;
switch (image->target)
{
case GL_TEXTURE_1D:
glTexStorage1D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width); //根據從dds中讀取到的紋理資料，分配紋理記憶體，設定紋理格式。
for (level = 0; level < image->mipLevels; ++level)
{
glTexSubImage1D(GL_TEXTURE_1D,
level,
0,
image->mip[level].width,
image->format, image->type,
image->mip[level].data);//設定資料，minmap
}
break;
case GL_TEXTURE_1D_ARRAY:
glTexStorage2D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width,
image->slices);
for (level = 0; level < image->mipLevels; ++level)
{
glTexSubImage2D(GL_TEXTURE_1D,
level,
0, 0,
image->mip[level].width, image->slices,
image->format, image->type,
image->mip[level].data);
}
break;
case GL_TEXTURE_2D:
glTexStorage2D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width,
image->mip[0].height);
for (level = 0; level < image->mipLevels; ++level)
{
glTexSubImage2D(GL_TEXTURE_2D,
level,
0, 0,
image->mip[level].width, image->mip[level].height,
image->format, image->type,
image->mip[level].data);
}
break;
case GL_TEXTURE_CUBE_MAP:
for (level = 0; level < image->mipLevels; ++level)
{
ptr = (GLubyte *)image->mip[level].data;
for (int face = 0; face < 6; face++)
{
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + face,
level,
image->internalFormat,
image->mip[level].width, image->mip[level].height,
0,
image->format, image->type,
ptr + image->sliceStride * face);
}
}
break;
case GL_TEXTURE_2D_ARRAY:
glTexStorage3D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width,
image->mip[0].height,
image->slices);
for (level = 0; level < image->mipLevels; ++level)
{
glTexSubImage3D(GL_TEXTURE_2D_ARRAY,
level,
0, 0, 0,
image->mip[level].width, image->mip[level].height, image->slices,
image->format, image->type,
image->mip[level].data);
}
break;
case GL_TEXTURE_CUBE_MAP_ARRAY:
glTexStorage3D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width,
image->mip[0].height,
image->slices);
break;
case GL_TEXTURE_3D:
glTexStorage3D(image->target,
image->mipLevels,
image->internalFormat,
image->mip[0].width,
image->mip[0].height,
image->mip[0].depth);
for (level = 0; level < image->mipLevels; ++level)
{
glTexSubImage3D(GL_TEXTURE_3D,
level,
0, 0, 0,
image->mip[level].width, image->mip[level].height, image->mip[level].depth,
image->format, image->type,
image->mip[level].data);
}
break;
default:
break;
}
glTexParameteriv(image->target, GL_TEXTURE_SWIZZLE_RGBA, reinterpret_cast<const GLint *>(image->swizzle));
if (image == &local_image)
{
vglUnloadImage(image);
}
return texture;
}
#include "vermilion.h"
#include "loadTexture.h"
#include "vbm.h"
#include "vmath.h"
#include "vutils.h"
namespace loadTexture
{
float aspect = 800.0f/600.0f;
GLuint base_prog;
GLuint vao;
GLuint quad_vbo;
GLuint tex;
};
using namespace loadTexture;
void loadTextureInit()
{
base_prog = glCreateProgram();
static const char quad_shader_vs[] =
"#version 330 core\n"
"\n"
"layout (location = 0) in vec2 in_position;\n"
"layout (location = 1) in vec2 in_tex_coord;\n"
"\n"
"out vec2 tex_coord;\n"
"\n"
"void main(void)\n"
"{\n"
" gl_Position = vec4(in_position, 0.5, 1.0);\n"
" tex_coord = in_tex_coord;\n"//把紋理座標傳遞給下一階段。
"}\n"
;
static const char quad_shader_fs[] =
"#version 330 core\n"
"\n"
"in vec2 tex_coord;\n"
"\n"
"layout (location = 0) out vec4 color;\n"
"\n"
"uniform sampler2D tex;\n"
"\n"
"void main(void)\n"
"{\n"
" color = texture(tex, tex_coord);\n"//texture 根據紋理座標採集紋素。
"}\n"
;
vglAttachShaderSource( base_prog, GL_VERTEX_SHADER, quad_shader_vs );
vglAttachShaderSource( base_prog, GL_FRAGMENT_SHADER, quad_shader_fs );
glGenBuffers( 1, &quad_vbo );
glBindBuffer( GL_ARRAY_BUFFER, quad_vbo );
static const GLfloat quad_data[] =
{
0.5f, -0.5f,
-1.0f, -1.0f,
-1.0f, 1.0f,
1.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 1.0f
};
glBufferData( GL_ARRAY_BUFFER, sizeof(quad_data), quad_data, GL_STATIC_DRAW );
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) ); //設定頂點著色器的輸出，頂點座標
glVertexAttribPointer( 1, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET( 8 * sizeof(float) ) );//頂點資料，紋理座標
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glLinkProgram( base_prog );
//char buf[1024];
//glGetProgramInfoLog( base_prog, 1024, NULL, buf );
vglImageData image;
tex = vglLoadTexture("../8edlib/media/test.dds", 0, &image ); //內部實現了紋理載入操作glGenTexture(),glBindTexture(),glStorage*(),glTexSubImage*()
glTexParameteri( image.target, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR ); //紋理縮小過濾模式
vglUnloadImage(&image);//紋理資訊已經儲存在紋理物件當中，釋放記憶體
}
void loadTextureDisplay()
{
float t = float(GetTickCount() & 0x3FFF) / float(0x3FFF);
static const vmath::vec3 X(1.0f, 0.0f, 0.0f);
static const vmath::vec3 Y(0.0f, 1.0f, 0.0f);
static const vmath::vec3 Z(0.0f, 0.0f, 1.0f);
glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
glClearDepth( 1.0f );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glDisable( GL_CULL_FACE );//禁用剔除操作
glUseProgram( base_prog );
glBindVertexArray( vao );
glDrawArrays( GL_TRIANGLE_FAN, 0, 4 );//扇形三角形繪製
}
void loadTextureUpdate(float delta)
{
}b、紋理座標越界控制
#include "commonHead.h"
#include "vbm.h"
#include "vutils.h"
namespace textureWrap
{
float aspect = 800.0f/600.0f;
GLuint base_prog;
GLuint vao;
GLuint quad_vbo;
GLuint tex;
};
using namespace textureWrap;
void textureWrapInit()
{
base_prog = glCreateProgram();
static const char quad_shader_vs[] =
"#version 330 core\n"
"\n"
"layout (location = 0) in vec2 in_position;\n"
"layout (location = 1) in vec2 in_tex_coord;\n"
"\n"
"out vec2 tex_coord;\n"
"\n"
"void main(void)\n"
"{\n"
" gl_Position = vec4(in_position, 0.5, 1.0);\n"
" tex_coord = in_tex_coord;\n"
"}\n"
;
static const char quad_shader_fs[] =
"#version 330 core\n"
"\n"
"in vec2 tex_coord;\n"
"\n"
"layout (location = 0) out vec4 color;\n"
"\n"
"uniform sampler2D tex;\n"
"\n"
"void main(void)\n"
"{\n"
" color = texture(tex, tex_coord);\n"
"}\n"
;
vglAttachShaderSource( base_prog, GL_VERTEX_SHADER, quad_shader_vs );
vglAttachShaderSource( base_prog, GL_FRAGMENT_SHADER, quad_shader_fs );
glGenBuffers( 1, &quad_vbo );
glBindBuffer( GL_ARRAY_BUFFER, quad_vbo );
static const GLfloat quad_data[] =
{
-0.75f, -0.75f,
0.75f, -0.75f,
0.75f, 0.75f,
-0.75f, 0.75f,
0.0f, 0.0f,
4.0f, 0.0f,
4.0f, 4.0f,
0.0f, 4.0f
};
glBufferData( GL_ARRAY_BUFFER, sizeof(quad_data), quad_data, GL_STATIC_DRAW );
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) );
glVertexAttribPointer( 1, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET( 8 * sizeof(float) ) );
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glLinkProgram( base_prog );
glGenTextures( 1, &tex );
glBindTexture( GL_TEXTURE_2D, tex );
glTexStorage2D( GL_TEXTURE_2D, 4, GL_RGBA8, 8, 8 ); //分配記憶體，不可改變
static const unsigned char texture_data[] =
{
0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00,
0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF,
0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00,
0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF,
0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00,
0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF,
0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00,
0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF
};
glTexSubImage2D( GL_TEXTURE_2D, 0, 0, 0, 8, 8, GL_RED, GL_UNSIGNED_BYTE, texture_data );//資料初始化
static const GLint swizzles[] = { GL_RED, GL_RED, GL_RED, GL_ONE };//只使用紋理的紅色通道
glTexParameteriv( GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_RGBA, swizzles );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );//紋理過濾函式，縮小
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );//紋理過濾函式，放大
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );//超出-1.0~1.0f的紋理座標處理方式設定s方向
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );//t方向
glGenerateMipmap( GL_TEXTURE_2D );//產生層級紋理。
}
void textureWrapUpdate(float)
{
}
void textureWrapDisplay()
{
unsigned int ticks = GetTickCount();
float t = float(ticks & 0x3FFF) / float(0x3FFF);
static const vmath::vec3 X(1.0f, 0.0f, 0.0f);
static const vmath::vec3 Y(0.0f, 1.0f, 0.0f);
static const vmath::vec3 Z(0.0f, 0.0f, 1.0f);
glClearColor( 0.3f, 0.3f, 0.3f, 1.0f );
glClearDepth( 1.0f );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glDisable( GL_CULL_FACE );
glUseProgram( base_prog );
static const GLenum wrap_modes[] = { GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER, GL_REPEAT, GL_MIRRORED_REPEAT };
//GL_CLAMP_TO_EDGE : 當紋理座標超出0.0—1.0時，使用紋理邊緣的紋素返回。
//GL_CLAMP_TO_BORDER : 讀取紋理範圍之外的卓彪將生成用來形成最總的紋理常數邊界顏色。可以通過glTexParameterfv()以GL_TEXTURE_BORDER_COLOR為引數設定邊界顏色值。
//GL_REPEAT : 包裹紋理，無限重複，只有紋理座標的小數部分用來生成紋理座標，整數部分被拋棄。
//GL_MIRRORED_REPEAT : 是一個特殊的模式，紋理可以以映象模式重複。整數部分是偶數的紋理座標只考慮小數部分，整數部分是奇數的紋理座標是1.0減去其小數部分來形成最終座標。
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrap_modes[3] );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrap_modes[3] );
glBindVertexArray( vao );
glDrawArrays( GL_TRIANGLE_FAN, 0, 4 );
}#include "multiTexture\multiTexture.h"
#include "vbm.h"
#include "vutils.h"
#include "vermilion.h"
namespace multiTexture
{
float aspect = 800.0f/600.0f;
GLuint base_prog;
GLuint vao;
GLuint quad_vbo;
GLuint tex1;
GLuint tex2;
GLint time_loc;
};
using namespace multiTexture;
void multiTextureInit()
{
base_prog = glCreateProgram();
static const char quad_shader_vs[] =
"#version 330 core\n"
"\n"
"layout (location = 0) in vec2 in_position;\n"
"layout (location = 1) in vec2 in_tex_coord;\n"
"\n"
"out vec2 tex_coord0;\n"
"out vec2 tex_coord1;\n"
"\n"
"uniform float time;\n"
"\n"
"void main(void)\n"
"{\n"
" mat2 m = mat2( vec2(cos(time), sin(time)),\n" //書中原始碼這裡定義的是const mat2是會產生連線時錯誤，因為m是根據時間而改變的，不可以為const
" vec2(-sin(time), cos(time)) );\n"
" gl_Position = vec4(in_position, 0.5, 1.0);\n"
" tex_coord0 = in_tex_coord * m;\n"
" tex_coord1 = in_tex_coord * transpose(m);\n"//構造的是一個旋轉矩陣，
"}\n"
;
static const char quad_shader_fs[] =
"#version 330 core\n"
"\n"
"in vec2 tex_coord0;\n"
"in vec2 tex_coord1;\n"
"\n"
"layout (location = 0) out vec4 color;\n"
"\n"
"uniform sampler2D tex1;\n" //sampler1
"uniform sampler2D tex2;\n" //sampler2
"\n"
"void main(void)\n"
"{\n"
" color = texture(tex1, tex_coord0) + texture(tex2, tex_coord1);\n" //對兩個紋理取樣進行混合，add
"}\n"
;
vglAttachShaderSource( base_prog, GL_VERTEX_SHADER, quad_shader_vs );
vglAttachShaderSource(base_prog, GL_FRAGMENT_SHADER, quad_shader_fs);
glGenBuffers( 1, &quad_vbo );
glBindBuffer( GL_ARRAY_BUFFER, quad_vbo );
static const GLfloat quad_data[] =
{
1.0f, -1.0f,
-1.0f, -1.0f,
-1.0f, 1.0f,
1.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 1.0f
};
glBufferData( GL_ARRAY_BUFFER, sizeof(quad_data), quad_data, GL_STATIC_DRAW );
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) );
glVertexAttribPointer( 1, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET( sizeof(float) * 8 ) );
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glLinkProgram( base_prog );
char buf[1024];
glGetProgramInfoLog(base_prog, 1024, NULL, buf);
glUseProgram(base_prog);
time_loc = glGetUniformLocation( base_prog, "time" );
glUniform1i(glGetUniformLocation(base_prog, "tex1"), 0);
glUniform1i( glGetUniformLocation(base_prog, "tex2"), 1);
vglImageData image;
tex1 = vglLoadTexture("../8edlib/media/test.dds", 0, &image );
glBindTexture( image.target, tex1 );
glTexParameteri( image.target, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
vglUnloadImage( &image );
tex2 = vglLoadTexture("../8edlib/media/test3.dds", 0, &image);
vglUnloadImage( &image );
}
void multiTextureDisplay()
{
float t = float(GetTickCount() & 0x3FFF) / float(0x3FFF);
static const vmath::vec3 X(1.0f, 0.0f, 0.0f);
static const vmath::vec3 Y(0.0f, 1.0f, 0.0f);
static const vmath::vec3 Z(0.0f, 0.0f, 1.0f);
glClearColor( 0.0f, 1.0f, 0.0f, 1.0f );
glClearDepth( 1.0f );
glDisable( GL_CULL_FACE );
glUseProgram( base_prog );
glUniform1f( time_loc, t );
glBindVertexArray( vao );
glActiveTexture( GL_TEXTURE0 ); //啟用紋理單元0
glBindTexture( GL_TEXTURE_2D, tex1 );
glActiveTexture( GL_TEXTURE1 ); //啟用紋理單元1
glBindTexture(GL_TEXTURE_2D, tex2 );
glDrawArrays( GL_TRIANGLE_FAN, 0, 4 );
GLenum errcode = glGetError();
const char* buf1 = (const char*)glewGetErrorString(errcode);
}
void multiTextureUpdate(float delta)
{
}