九、OpenGL纹理练习之绘制隧道

这次我们利用学习的OpenGL纹理的知识绘制一个隧道，具体效果见下图

生成纹理标记并设置纹理参数（过滤方式，环绕方式）

 GLbyte *pBytes;
 
GLint iWidth, iHeight, iComponents;
GLenum eFormat;
GLint iLoop;

//3.生成纹理标记
/** 分配纹理对象 glGenTextures
 参数1：纹理对象的数量
 参数2：纹理对象标识数组
 */
glGenTextures(TEXTURE_COUNT, textures);

//4. 循环设置纹理数组的纹理参数
for(iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
{
    /**绑定纹理对象 glBindTexture
     参数1：纹理模式，GL_TEXTURE_1D,GL_TEXTURE_2D,GL_TEXTURE_3D
     参数2：需要绑定的纹理对象
     */
    glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
    
    /**加载tga文件
     参数1：纹理文件名称
     参数2：文件宽度变量地址
     参数3：文件高度变量地址
     参数4：文件组件变量地址
     参数5：文件格式变量地址
     返回值：pBytes，指向图像数据的指针
     */
    
    pBytes = gltReadTGABits(szTextureFiles[iLoop],&iWidth, &iHeight,
                            &iComponents, &eFormat);
    
    //加载纹理、设置过滤器和包装模式
    //GL_TEXTURE_MAG_FILTER（放大过滤器,GL_NEAREST(最邻近过滤)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    //GL_TEXTURE_MIN_FILTER(缩小过滤器),GL_NEAREST(最邻近过滤)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    //GL_TEXTURE_WRAP_S(s轴环绕),GL_CLAMP_TO_EDGE(环绕模式强制对范围之外的纹理坐标沿着合法的纹理单元的最后一行或一列进行采样)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    //GL_TEXTURE_WRAP_T(t轴环绕)，GL_CLAMP_TO_EDGE(环绕模式强制对范围之外的纹理坐标沿着合法的纹理单元的最后一行或一列进行采样)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    
    
    /**载入纹理 glTexImage2D
     参数1：纹理维度，GL_TEXTURE_2D
     参数2：mip贴图层次
     参数3：纹理单元存储的颜色成分（从读取像素图中获得）
     参数4：加载纹理宽度
     参数5：加载纹理的高度
     参数6：加载纹理的深度
     参数7：像素数据的数据类型,GL_UNSIGNED_BYTE无符号整型
     参数8：指向纹理图像数据的指针
     */
    glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes);
    
        /**为纹理对象生成一组完整的mipmap glGenerateMipmap
         参数1：纹理维度，GL_TEXTURE_1D,GL_TEXTURE_2D,GL_TEXTURE_2D
         */
        glGenerateMipmap(GL_TEXTURE_2D);
    
        //释放原始纹理数据，不在需要纹理原始数据了
        free(pBytes);
}

设置几何图形顶点/纹理坐标(上.下.左.右)

GLfloat z;

/*
 GLTools库中的容器类，GBatch，
 void GLBatch::Begin(GLenum primitive,GLuint nVerts,GLuint nTextureUnits = 0);
 参数1：图元枚举值
 参数2：顶点数
 参数3：1组或者2组纹理坐标
 */

floorBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
//参考PPT图6-10
//Z表示深度，隧道的深度
for(z = 60.0f; z >= 0.0f; z -=10.0f)
{
    floorBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
    floorBatch.Vertex3f(-10.0f, -10.0f, z);
    
    floorBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
    floorBatch.Vertex3f(10.0f, -10.0f, z);
    
    floorBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
    floorBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);
    
    floorBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
    floorBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);
}
floorBatch.End();

 
ceilingBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
for(z = 60.0f; z >= 0.0f; z -=10.0f)
{
    ceilingBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
    ceilingBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);
    
    ceilingBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
    ceilingBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);
    
    ceilingBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
    ceilingBatch.Vertex3f(-10.0f, 10.0f, z);
    
    ceilingBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
    ceilingBatch.Vertex3f(10.0f, 10.0f, z);
}
ceilingBatch.End();
leftWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
for(z = 60.0f; z >= 0.0f; z -=10.0f)
{
    leftWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
    leftWallBatch.Vertex3f(-10.0f, -10.0f, z);
    
    leftWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
    leftWallBatch.Vertex3f(-10.0f, 10.0f, z);
    
    leftWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
    leftWallBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);
    
    leftWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
    leftWallBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);
}
leftWallBatch.End();

 //
rightWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
for(z = 60.0f; z >= 0.0f; z -=10.0f)
{
    rightWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
    rightWallBatch.Vertex3f(10.0f, -10.0f, z);
    
    rightWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
    rightWallBatch.Vertex3f(10.0f, 10.0f, z);
    
    rightWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
    rightWallBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);
    
    rightWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
    rightWallBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);
}
rightWallBatch.End();

改变视景体和视口，在改变窗口大小或初始化窗口调用

 void ChangeSize(int w, int h)
 {
//1.防止对0进行除法操作
if(h == 0)
    h = 1;

//2.将视口设置大小
glViewport(0, 0, w, h);

GLfloat fAspect = (GLfloat)w/(GLfloat)h;

//3.生成透视投影
viewFrustum.SetPerspective(80.0f,fAspect,1.0,120.0);
projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);

 }

绘制场景

 //调用，绘制场景
 void RenderScene(void)
 {
//1.用当前清除色，清除窗口
glClear(GL_COLOR_BUFFER_BIT);

//2.模型视图压栈
modelViewMatrix.PushMatrix();
//Z轴平移viewZ 距离
modelViewMatrix.Translate(0.0f, 0.0f, viewZ);

//3.纹理替换矩阵着色器
/*
 参数1：GLT_SHADER_TEXTURE_REPLACE（着色器标签）
 参数2：模型视图投影矩阵
 参数3：纹理层
 */
shaderManager.UseStockShader(GLT_SHADER_TEXTURE_REPLACE, transformPipeline.GetModelViewProjectionMatrix(), 0);

//4.绑定纹理
/*
 参数1：纹理模式，GL_TEXTURE_1D、GL_TEXTURE_2D、GL_TEXTURE_3D
 参数2：需要绑定的纹理
 */
glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_FLOOR]);
floorBatch.Draw();

glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_CEILING]);
ceilingBatch.Draw();

glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_BRICK]);
leftWallBatch.Draw();
rightWallBatch.Draw();

//5.pop
modelViewMatrix.PopMatrix();

//6.缓存区交换
glutSwapBuffers();
}