OpenGL GLSL访问纹理

这一节我们给上一节的ADSPhone的程序贴上一张纹理贴图

如下图：

GLSL访问纹理很简单，只需要把要使用的纹理坐标和纹理的对象传入着色器即可

对于本程序，我们把纹理坐标和纹理对象传入顶点着色器ADSTexture.vp中，在片段着色器ADSTexture.fp计算颜色值时 乘上 纹理的颜色值，其余的ADSPhone的程序都一样

下面是顶点着色器ADSTexture.vp的所有代码，每一句都有注释

// 要求OpenGL的版本最低是1.3#version 130// 需要从外界传入的字段//顶点in vec4 vVertex;//顶点法线in vec3 vNormal;//纹理对象in vec4 vTexture0;//模型视图变换矩阵uniform mat4   mvpMatrix;//视图变换矩阵uniform mat4   mvMatrix;//模型视图变换矩阵法线矩阵uniform mat3   normalMatrix;//光源的位置uniform vec3   vLightPosition;//需要传入片段着色器的字段//面法线smooth out vec3 vVaryingNormal;//光源的方向smooth out vec3 vVaryingLightDir;//纹理坐标smooth out vec2 vTexCoords;void main(void)     { // 得到法线在照相机坐标系下的位置vVaryingNormal = normalMatrix * vNormal;// 得到顶点在照相机坐标系下的位置vec4 vPosition4 = mvMatrix * vVertex;vec3 vPosition3 = vPosition4.xyz / vPosition4.w;// 得到光源方向vVaryingLightDir = normalize(vLightPosition - vPosition3);// 得到纹理坐标vTexCoords = vTexture0.st;// 把顶点变换到照相机坐标系下gl_Position = mvpMatrix * vVertex;    }

下面是片段着色器ADSTexture.fp的所有代码

#version 130//传出到光栅化阶段的颜色值out vec4 vFragColor;//环境光颜色值uniform vec4      ambientColor;//漫反射光颜色值uniform vec4      diffuseColor;   //镜面光颜色值uniform vec4      specularColor;//纹理对象uniform sampler2D colorMap;//从顶点着色器传入的值//面法线smooth in vec3 vVaryingNormal;//光源的方向smooth in vec3 vVaryingLightDir;//纹理坐标smooth in vec2 vTexCoords;void main(void)    { // 计算漫反射光强度float diff = max(0.0, dot(normalize(vVaryingNormal), normalize(vVaryingLightDir)));// 漫反射光强度 乘上 漫反射光颜色值vFragColor = diff * diffuseColor;// 加上环境光颜色值vFragColor += ambientColor;// 乘上纹理颜色值vFragColor *= texture(colorMap, vTexCoords);// 加上镜面光颜色值vec3 vReflection = normalize(reflect(-normalize(vVaryingLightDir), normalize(vVaryingNormal)));float spec = max(0.0, dot(normalize(vVaryingNormal), vReflection));if(diff != 0) {float fSpec = pow(spec, 128.0);vFragColor.rgb += vec3(fSpec, fSpec, fSpec);}    }

下面是OpenGL工程中的代码

首先我们来看一下需要包含的头文件和全局变量

#include <GLTools.h>#include <GLMatrixStack.h>#include <GLFrame.h>#include <GLFrustum.h>#include <GLGeometryTransform.h>#include <StopWatch.h>#include <math.h>#define FREEGLUT_STATIC#include <GL/glut.h>GLFrame             viewFrame;GLFrustum           viewFrustum;GLTriangleBatch     sphereBatch;GLMatrixStack       modelViewMatrix;GLMatrixStack       projectionMatrix;GLGeometryTransform transformPipeline;GLShaderManager     shaderManager;GLuintADSTextureShader;//着色器中的统一值(uniform)GLintlocAmbient;GLint   locDiffuse;GLint   locSpecular; GLintlocLight;GLintlocMVP;GLintlocMV;GLintlocNM;GLint   locTexture;//纹理对象GLuint  texture;

下面是主函数main

int main(int argc, char* argv[])    {//设置工程路径gltSetWorkingDirectory(argv[0]);//初始化GLUTglutInit(&argc, argv);//设置需要使用的窗口模式glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);//窗口的大小glutInitWindowSize(800, 600);//窗口的名字glutCreateWindow("Lit Texture");//窗口大小改变时的回调函数glutReshapeFunc(ChangeSize);//渲染时的回调函数glutDisplayFunc(RenderScene);//初始化glewGLenum err = glewInit();if (GLEW_OK != err) {fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));return 1;}//初始化函数SetupRC();    //消息循环glutMainLoop();//程序退出时的清理工作ShutdownRC();return 0;    }

下面是窗口改变时的回调函数ChangeSize

void ChangeSize(int w, int h){// Prevent a divide by zeroif(h == 0)h = 1;//设置视口大小glViewport(0, 0, w, h);//设置投影变换矩阵viewFrustum.SetPerspective(35.0f, float(w)/float(h), 1.0f, 100.0f);//设置模型变换矩阵projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);}

下面是初始化函数SetupRC

void SetupRC(void){// BackgroundglClearColor(0.0f, 0.0f, 0.0f, 1.0f );glEnable(GL_DEPTH_TEST);glEnable(GL_CULL_FACE);shaderManager.InitializeStockShaders();viewFrame.MoveForward(4.0f);//创建小球模型数据gltMakeSphere(sphereBatch, 1.0f, 26, 13);//加载自己写的着色器ADSTextureShader = gltLoadShaderPairWithAttributes("ADSTexture.vp", "ADSTexture.fp", 3, GLT_ATTRIBUTE_VERTEX, "vVertex",GLT_ATTRIBUTE_NORMAL, "vNormal", GLT_ATTRIBUTE_TEXTURE0, "vTexture0");//得到统一值在着色器程序中的位置引用，以便我们给它赋值locAmbient = glGetUniformLocation(ADSTextureShader, "ambientColor");locDiffuse = glGetUniformLocation(ADSTextureShader, "diffuseColor");locSpecular = glGetUniformLocation(ADSTextureShader, "specularColor");locLight = glGetUniformLocation(ADSTextureShader, "vLightPosition");locMVP = glGetUniformLocation(ADSTextureShader, "mvpMatrix");locMV  = glGetUniformLocation(ADSTextureShader, "mvMatrix");locNM  = glGetUniformLocation(ADSTextureShader, "normalMatrix");locTexture = glGetUniformLocation(ADSTextureShader, "colorMap");//创建一个纹理对象glGenTextures(1, &texture);//绑定一个纹理对象glBindTexture(GL_TEXTURE_2D, texture);//加载纹理LoadTGATexture("CoolTexture.tga", GL_LINEAR_MIPMAP_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE);}

下面是纹理加载函数LoadTGATexture

bool LoadTGATexture(const char *szFileName, GLenum minFilter, GLenum magFilter, GLenum wrapMode){GLbyte *pBits;int nWidth, nHeight, nComponents;GLenum eFormat;//从文件中读取纹理的数据pBits = gltReadTGABits(szFileName, &nWidth, &nHeight, &nComponents, &eFormat);if(pBits == NULL) return false;//设置纹理环绕模式glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapMode);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapMode);//设置纹理过滤模式glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);    //设置文理数据的内存字节对齐方式glPixelStorei(GL_UNPACK_ALIGNMENT, 1);//生成纹理glTexImage2D(GL_TEXTURE_2D, 0, nComponents, nWidth, nHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBits);    free(pBits);    //设置mip贴图    if(minFilter == GL_LINEAR_MIPMAP_LINEAR ||        minFilter == GL_LINEAR_MIPMAP_NEAREST ||       minFilter == GL_NEAREST_MIPMAP_LINEAR ||       minFilter == GL_NEAREST_MIPMAP_NEAREST)        glGenerateMipmap(GL_TEXTURE_2D);    return true;}

下面是渲染函数RenderScene

void RenderScene(void){static CStopWatch rotTimer;// Clear the window and the depth bufferglClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);modelViewMatrix.PushMatrix(viewFrame);modelViewMatrix.Rotate(rotTimer.GetElapsedSeconds() * 10.0f, 0.0f, 1.0f, 0.0f);GLfloat vEyeLight[] = { -100.0f, 100.0f, 100.0f };GLfloat vAmbientColor[] = { 0.2f, 0.2f, 0.2f, 1.0f };GLfloat vDiffuseColor[] = { 1.0f, 1.0f, 1.0f, 1.0f };GLfloat vSpecularColor[] = { 1.0f, 1.0f, 1.0f, 1.0f };//绑定纹理对象glBindTexture(GL_TEXTURE_2D, texture);//使用自己写的着色器glUseProgram(ADSTextureShader);//设置统一值glUniform4fv(locAmbient, 1, vAmbientColor);glUniform4fv(locDiffuse, 1, vDiffuseColor);glUniform4fv(locSpecular, 1, vSpecularColor);glUniform3fv(locLight, 1, vEyeLight);glUniformMatrix4fv(locMVP, 1, GL_FALSE, transformPipeline.GetModelViewProjectionMatrix());glUniformMatrix4fv(locMV, 1, GL_FALSE, transformPipeline.GetModelViewMatrix());glUniformMatrix3fv(locNM, 1, GL_FALSE, transformPipeline.GetNormalMatrix());glUniform1i(locTexture, 0);//绘制模型sphereBatch.Draw();modelViewMatrix.PopMatrix();glutSwapBuffers();glutPostRedisplay();}

下面是程序退出时的清理函数ShutdownRC

void ShutdownRC(void)   {//删除纹理对象glDeleteTextures(1, &texture);   }