OpenGL 光照贴图

1.简介

现实世界中的物体通常并不只包含有一种材质，而是由多种材质所组成。想想一辆汽车：它的外壳非常有光泽，车窗会部分反射周围的环境，轮胎不会那么有光泽，所以它没有镜面高光，轮毂非常闪亮。

2.漫反射贴图

用一张覆盖物体的图像，让我们能够逐片段索引其独立的颜色值，它是一个表现了物体所有的漫反射颜色的纹理图像。

这次我们会将纹理储存为Material结构体中的一个sampler2D。我们将之前定义的vec3漫反射颜色向量替换为漫反射贴图。移除了环境光材质颜色向量，因为环境光颜色在几乎所有情况下都等于漫反射颜色，所以我们不需要将它们分开储存：

struct Material {sampler2D diffuse;vec3      specular;float     shininess;
};
...
in vec2 TexCoords;

接下来我们只需要从纹理中采样片段的漫反射颜色值即可：

    vec3 diffuseTexColor = vec3(texture(material.diffuse,TexCoords));//diffusevec3 norm = normalize(outNormal);vec3 lightDir = normalize(lightPos - FragPos);float diff = max(dot(norm, lightDir), 0.0);vec3 diffuse = light.diffuse * diff * diffuseTexColor;

不要忘记将环境光的材质颜色设置为漫反射材质颜色同样的值。

    //ambinetvec3 ambient = light.ambient * diffuseTexColor;

3.镜面光贴图

你可能会注意到，镜面高光看起来有些奇怪，因为我们的物体大部分都是木头，我们知道木头不应该有这么强的镜面高光的。我们可以将物体的镜面光材质设置为vec3(0.0)来解决这个问题，但这也意味着箱子钢制的边框将不再能够显示镜面高光了，我们知道钢铁应该是有一些镜面高光的。

我们同样可以使用一个专门用于镜面高光的纹理贴图。这也就意味着我们需要生成一个黑白的纹理，来定义物体每部分的镜面光强度。

由于箱子大部分都由木头所组成，而且木头材质应该没有镜面高光，所以漫反射纹理的整个木头部分全部都转换成了黑色。箱子钢制边框的镜面光强度是有细微变化的，钢铁本身会比较容易受到镜面高光的影响，而裂缝则不会。

接下来更新片段着色器的材质属性，让其接受一个sampler2D而不是vec3作为镜面光分量：

struct Material {sampler2D diffuse;sampler2D specular;float     shininess;
};

4.示例

#include "myopenglwidget.h"
#include <QMatrix4x4>
#include <QTime>
#include <QTimer>
#include <math.h>
#include <QDebug>float vertices[] = {// positions          // normals           // texture coords-0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  0.0f, 0.0f,0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f, 0.0f,0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f, 1.0f,0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f, 1.0f,-0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  0.0f, 1.0f,-0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  0.0f, 0.0f,-0.5f, -0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   0.0f, 0.0f,0.5f, -0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   1.0f, 0.0f,0.5f,  0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   1.0f, 1.0f,0.5f,  0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   1.0f, 1.0f,-0.5f,  0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   0.0f, 1.0f,-0.5f, -0.5f,  0.5f,  0.0f,  0.0f, 1.0f,   0.0f, 0.0f,-0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  1.0f, 0.0f,-0.5f,  0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  1.0f, 1.0f,-0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  0.0f, 1.0f,-0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  0.0f, 1.0f,-0.5f, -0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  0.0f, 0.0f,-0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  1.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  1.0f, 0.0f,0.5f,  0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  1.0f, 1.0f,0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  0.0f, 1.0f,0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  0.0f, 1.0f,0.5f, -0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  0.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  1.0f, 0.0f,-0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  0.0f, 1.0f,0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  1.0f, 1.0f,0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  1.0f, 0.0f,0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  1.0f, 0.0f,-0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  0.0f, 0.0f,-0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  0.0f, 1.0f,-0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  0.0f, 1.0f,0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  1.0f, 1.0f,0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  1.0f, 0.0f,0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  1.0f, 0.0f,-0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  0.0f, 0.0f,-0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  0.0f, 1.0f
};GLuint indices[] = {0, 1, 3,1, 2, 3
};GLuint VBO, VAO,EBO,lightVAO;
GLuint shaderProgram;QVector3D lightPos(1.2f,1.0f,2.0f);
QVector3D lightColor(1.0f,1.0f,1.0f);
QVector3D objectColor(1.0f,0.5f,0.31f);QTimer *timer;
QTime gtime;QVector<QVector3D> cubePositions = {QVector3D( 0.0f,  0.0f,  0.0f),QVector3D( 2.0f,  5.0f, -15.0f),QVector3D(-1.5f, -2.2f, -2.5f),QVector3D(-3.8f, -2.0f, -12.3f),QVector3D( 2.4f, -0.4f, -3.5f),QVector3D(-1.7f,  3.0f, -7.5f),QVector3D( 1.3f, -2.0f, -2.5f),QVector3D( 1.5f,  2.0f, -2.5f),QVector3D( 1.5f,  0.2f, -1.5f),QVector3D(-1.3f,  1.0f, -1.5f)
};float fov = 45.0f;MyOpenGLWidget::MyOpenGLWidget(QWidget *parent): QOpenGLWidget(parent)
{cameraPos = QVector3D( 0.0f,  0.0f,  5.0f);//摄像机位置cameraTarget = QVector3D( 0.0f,  0.0f,  0.0f);//摄像机看到的位置cameraDirection = QVector3D(cameraPos - cameraTarget);//摄像机的方向cameraDirection.normalize();up = QVector3D(0.0f,  1.0f,  0.0f);cameraRight = QVector3D::crossProduct(up,cameraDirection);//两个向量叉乘的结果会同时垂直于两向量，因此我们会得到指向x轴正方向的那个向量cameraRight.normalize();cameraUp = QVector3D::crossProduct(cameraDirection,cameraRight);cameraFront = QVector3D( 0.0f,  0.0f,  -1.0f);timer = new QTimer();timer->start(50);gtime.start();connect(timer,&QTimer::timeout,[=]{update();});setFocusPolicy(Qt::StrongFocus);//setMouseTracking(true);}void MyOpenGLWidget::initializeGL()
{initializeOpenGLFunctions();m_program = new QOpenGLShaderProgram();m_program->addShaderFromSourceFile(QOpenGLShader::Vertex,":/shapes.vert");m_program->addShaderFromSourceFile(QOpenGLShader::Fragment,":/shapes.frag");m_program->link();qDebug()<<m_program->log();m_lightProgram = new QOpenGLShaderProgram();m_lightProgram->addShaderFromSourceFile(QOpenGLShader::Vertex,":/light.vert");m_lightProgram->addShaderFromSourceFile(QOpenGLShader::Fragment,":/light.frag");m_lightProgram->link();glGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);glBindVertexArray(VAO);//绑定VAOglBindBuffer(GL_ARRAY_BUFFER, VBO);//顶点缓冲对象的缓冲类型是GL_ARRAY_BUFFERglBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//把顶点数据复制到缓冲的内存中GL_STATIC_DRAW ：数据不会或几乎不会改变。glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)0);glEnableVertexAttribArray(0);glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(3*sizeof(GLfloat)));glEnableVertexAttribArray(1);glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(6*sizeof(GLfloat)));glEnableVertexAttribArray(2);glGenBuffers(1, &EBO);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glGenVertexArrays(1, &lightVAO);glGenBuffers(1, &VBO);glBindVertexArray(lightVAO);//绑定VAOglBindBuffer(GL_ARRAY_BUFFER, VBO);//顶点缓冲对象的缓冲类型是GL_ARRAY_BUFFERglBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//把顶点数据复制到缓冲的内存中GL_STATIC_DRAW ：数据不会或几乎不会改变。glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);m_program->bind();m_program->setUniformValue("lightPos",lightPos);m_program->setUniformValue("viewPos",cameraPos);m_program->setUniformValue("material.shininess", 32.0f);m_diffseTexture = new QOpenGLTexture(QImage(":/container2.png").mirrored());m_program->setUniformValue("material.diffuse",0);m_specularTexture = new QOpenGLTexture(QImage(":/container2_specular.png").mirrored());m_program->setUniformValue("material.specular",1);m_lightProgram->bind();m_lightProgram->setUniformValue("lightColor",lightColor);glBindVertexArray(0);//解绑VAO}void MyOpenGLWidget::paintGL()
{glClearColor(0.2f,0.3f,0.3f,1.0f);glEnable(GL_DEPTH_TEST);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);QMatrix4x4 model;QMatrix4x4 view;float time = gtime.elapsed()/50.0;//int time = QTime::currentTime().msec();QMatrix4x4 projection;projection.perspective(fov,(float)( width())/(height()),0.1,100);view.lookAt(cameraPos,cameraPos + cameraFront,up);m_program->bind();m_program->setUniformValue("projection",projection);m_program->setUniformValue("view",view);lightColor.setX(sin(time/100 * 2.0f));lightColor.setY(sin(time/100 * 0.7f));lightColor.setZ(sin(time/100 * 1.3f));QVector3D diffuseColor = QVector3D(0.3f,0.3f,0.3f);QVector3D ambinetColor = QVector3D(0.7f,0.7f,0.7f);m_program->setUniformValue("light.ambient",  ambinetColor);m_program->setUniformValue("light.diffuse",  diffuseColor); // 将光照调暗了一些以搭配场景m_program->setUniformValue("light.specular", QVector3D(1.0,1.0,1.0));m_diffseTexture->bind(0);m_specularTexture->bind(1);glBindVertexArray(VAO);//绑定VAOmodel.rotate(time,1.0f,1.0f,0.5f);m_program->setUniformValue("model",model);glDrawArrays(GL_TRIANGLES,0,36);m_lightProgram->bind();m_lightProgram->setUniformValue("projection",projection);m_lightProgram->setUniformValue("view",view);//m_lightProgram->setUniformValue("lightColor",lightColor);model.setToIdentity();model.translate(lightPos);model.rotate(1.0f,1.0f,5.0f,0.5f);model.scale(0.2);m_lightProgram->setUniformValue("model",model);glBindVertexArray(lightVAO);//绑定VAOglDrawArrays(GL_TRIANGLES,0,36);//    foreach(auto pos , cubePositions)
//    {
//        model.setToIdentity();
//        model.translate(pos);
//        //model.rotate(time,1.0f,5.0f,3.0f);
//        m_program->setUniformValue("model",model);
//        glDrawArrays(GL_TRIANGLES,0,36);
//    }}void MyOpenGLWidget::resizeGL(int w, int h)
{}void MyOpenGLWidget::keyPressEvent(QKeyEvent *event)
{qDebug()<<event->key();cameraSpeed = 2.5 * 100 / 1000.0;switch (event->key()) {case Qt::Key_W:{cameraPos += cameraSpeed * cameraFront;}break;case Qt::Key_S:{cameraPos -= cameraSpeed * cameraFront;}break;case Qt::Key_A:{cameraPos -= cameraSpeed * cameraRight;}break;case Qt::Key_D:{cameraPos += cameraSpeed * cameraRight;}break;default:break;}update();
}
float PI = 3.1415926;
QPoint deltaPos;
void MyOpenGLWidget::mouseMoveEvent(QMouseEvent *event)
{
//    static float yaw = -90;
//    static float pitch = 0;
//    static QPoint lastPos(width()/2,height()/2);
//    auto currentPos = event->pos();
//    deltaPos = currentPos-lastPos;
//    lastPos=currentPos;
//    float sensitivity = 0.1f;
//    deltaPos *= sensitivity;
//    yaw += deltaPos.x();
//    pitch -= deltaPos.y();
//    if(pitch > 89.0f) pitch = 89.0f;
//    if(pitch < -89.0f) pitch = -89.0f;
//    cameraFront.setX(cos(yaw*PI/180.0) * cos(pitch *PI/180));
//    cameraFront.setY(sin(pitch*PI/180));
//    cameraFront.setZ(sin(yaw*PI/180) * cos(pitch *PI/180));
//    cameraFront.normalize();
//    update();
}void MyOpenGLWidget::wheelEvent(QWheelEvent *event)
{if(fov >= 1.0f && fov <= 75.0f)fov -= event->angleDelta().y()/120;if(fov <= 1.0f)fov = 1.0f;if(fov >= 75.0f)fov = 75.0f;update();
}