隧道源码示例
// Tunnel.cpp
// Demonstrates mipmapping and using texture objects
// OpenGL SuperBible
// Richard S. Wright Jr.
#include
#include
#include
#include
#include
#include
#include
#ifdef __APPLE__
#include
#else
#define FREEGLUT_STATIC
#include
#endif
GLShaderManager shaderManager; // Shader Manager
GLMatrixStack modelViewMatrix; // Modelview Matrix
GLMatrixStack projectionMatrix; // Projection Matrix
GLFrustum viewFrustum; // View Frustum
GLGeometryTransform transformPipeline; // Geometry Transform Pipeline
GLBatch floorBatch;
GLBatch ceilingBatch;
GLBatch leftWallBatch;
GLBatch rightWallBatch;
GLfloat viewZ = -65.0f;
// Texture objects
#define TEXTURE_BRICK 0
#define TEXTURE_FLOOR 1
#define TEXTURE_CEILING 2
#define TEXTURE_COUNT 3
GLuint textures[TEXTURE_COUNT];
const char *szTextureFiles[TEXTURE_COUNT] = { "brick.tga", "floor.tga", "ceiling.tga" };
///////////////////////////////////////////////////////////////////////////////
// Change texture filter for each texture object
void ProcessMenu(int value)
{
GLint iLoop;
for(iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
{
glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
switch(value)
{
case 0:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
break;
case 1:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
break;
case 2:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
break;
case 3:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_LINEAR);
break;
case 4:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
break;
case 5:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
break;
}
}
// Trigger Redraw
glutPostRedisplay();
}
//////////////////////////////////////////////////////////////////
// This function does any needed initialization on the rendering
// context. Here it sets up and initializes the texture objects.
void SetupRC()
{
GLbyte *pBytes;
GLint iWidth, iHeight, iComponents;
GLenum eFormat;
GLint iLoop;
// Black background
glClearColor(0.0f, 0.0f, 0.0f,1.0f);
shaderManager.InitializeStockShaders();
// Load textures
glGenTextures(TEXTURE_COUNT, textures);
for(iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
{
// Bind to next texture object
glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
// Load texture, set filter and wrap modes
pBytes = gltReadTGABits(szTextureFiles[iLoop],&iWidth, &iHeight,
&iComponents, &eFormat);
// Load texture, set filter and wrap modes
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes);
glGenerateMipmap(GL_TEXTURE_2D);
// Don't need original texture data any more
free(pBytes);
}
// Build Geometry
GLfloat z;
floorBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
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();
}
///////////////////////////////////////////////////
// Shutdown the rendering context. Just deletes the
// texture objects
void ShutdownRC(void)
{
glDeleteTextures(TEXTURE_COUNT, textures);
}
///////////////////////////////////////////////////
// Respond to arrow keys, move the viewpoint back
// and forth
void SpecialKeys(int key, int x, int y)
{
if(key == GLUT_KEY_UP)
viewZ += 0.5f;
if(key == GLUT_KEY_DOWN)
viewZ -= 0.5f;
// Refresh the Window
glutPostRedisplay();
}
/////////////////////////////////////////////////////////////////////
// Change viewing volume and viewport. Called when window is resized
void ChangeSize(int w, int h)
{
GLfloat fAspect;
// Prevent a divide by zero
if(h == 0)
h = 1;
// Set Viewport to window dimensions
glViewport(0, 0, w, h);
fAspect = (GLfloat)w/(GLfloat)h;
// Produce the perspective projection
viewFrustum.SetPerspective(80.0f,fAspect,1.0,120.0);
projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);
}
///////////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT);
modelViewMatrix.PushMatrix();
modelViewMatrix.Translate(0.0f, 0.0f, viewZ);
shaderManager.UseStockShader(GLT_SHADER_TEXTURE_REPLACE, transformPipeline.GetModelViewProjectionMatrix(), 0);
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();
modelViewMatrix.PopMatrix();
// Buffer swap
glutSwapBuffers();
}
//////////////////////////////////////////////////////
// Program entry point
int main(int argc, char *argv[])
{
gltSetWorkingDirectory(argv[0]);
// Standard initialization stuff
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(800, 600);
glutCreateWindow("Tunnel");
glutReshapeFunc(ChangeSize);
glutSpecialFunc(SpecialKeys);
glutDisplayFunc(RenderScene);
// Add menu entries to change filter
glutCreateMenu(ProcessMenu);
glutAddMenuEntry("GL_NEAREST",0);
glutAddMenuEntry("GL_LINEAR",1);
glutAddMenuEntry("GL_NEAREST_MIPMAP_NEAREST",2);
glutAddMenuEntry("GL_NEAREST_MIPMAP_LINEAR", 3);
glutAddMenuEntry("GL_LINEAR_MIPMAP_NEAREST", 4);
glutAddMenuEntry("GL_LINEAR_MIPMAP_LINEAR", 5);
glutAttachMenu(GLUT_RIGHT_BUTTON);
GLenum err = glewInit();
if (GLEW_OK != err) {
fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
return 1;
}
// Startup, loop, shutdown
SetupRC();
glutMainLoop();
ShutdownRC();
return 0;
}
运行时,按下前后方向键可前后行进。右键鼠标,有6个选项菜单,可以选择纹理贴图的过滤方式和Mip纹理贴图过滤方式。
通过上一个源码示例的学习,我们已经熟悉了纹理的一些应用的知识,着了解析学习一下新的渲染知识。
一、源码解析
1、全局变量定义
//上下左右墙壁的批次图元的定义
GLBatch floorBatch;
GLBatch ceilingBatch;
GLBatch leftWallBatch;
GLBatch rightWallBatch;
//视坐标Z轴平移的的像素值
GLfloat viewZ = -65.0f;
// 定义纹理标识和执行纹理贴图文件的指针
#define TEXTURE_BRICK 0
#define TEXTURE_FLOOR 1
#define TEXTURE_CEILING 2
#define TEXTURE_COUNT 3
GLuint textures[TEXTURE_COUNT];
const char *szTextureFiles[TEXTURE_COUNT] = { "brick.tga", "floor.tga", "ceiling.tga" };
2、函数解析
1)void SetupRC()
GLbyte *pBytes; //声明指向纹理数据的指针,
GLint iWidth, iHeight, iComponents; //返回的指向新的缓冲区、纹理的高低各宽度。
GLenum eFormat; //OpenGL图像数据格式
GLint iLoop; //循环加载纹理的局部变量
......
glGenTextures(TEXTURE_COUNT, textures); //生成纹理,注意是三个纹理标识符(数组)//循环绑定纹理标识符,并读取纹理贴图文件的数据
for(iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
{
//绑定纹理标识符
glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
//读取纹理贴图的纹理数据,与绑定的纹理标识符一一对应
pBytes = gltReadTGABits(szTextureFiles[iLoop],&iWidth, &iHeight,
&iComponents, &eFormat);
//设置纹理的过滤和环绕方式
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);//载入纹理数据
glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes);//生成Mip贴图层
glGenerateMipmap(GL_TEXTURE_2D);
//载入纹理数据之后可以释放纹理数据的临时指针
free(pBytes);
// 建立天花板的墙体图形
GLfloat z; //z轴的坐标值
floorBatch.Begin(GL_TRIANGLE_STRIP, 28, 1); //绘制线带(顶点连成线)//指定Mip贴图纹理层次,纹理坐标。以视坐标的z轴循环
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();
//左右和下面的墙体按照以上同样的方式建立图元
2)void RenderScene(void)
modelViewMatrix.PushMatrix(); //默认压栈单位矩阵到模型视图矩阵堆栈中
modelViewMatrix.Translate(0.0f, 0.0f, viewZ);//创建一个沿Z轴的平移矩阵再与模型视图矩阵堆栈顶部的矩阵相乘,再压栈到堆栈
//选择使用纹理提到换着色器,使用绑定到0指定的纹理单元的纹理对几何图形进行变换
shaderManager.UseStockShader(GLT_SHADER_TEXTURE_REPLACE, transformPipeline.GetModelViewProjectionMatrix(), 0);
//提交天花板墙体批次图元给着色器绘制渲染
glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_FLOOR]);
floorBatch.Draw();
//提交地面墙体批次图元给着色器绘制渲染
glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_CEILING]);
ceilingBatch.Draw()
//提交两侧墙体批次图元给着色器绘制渲染
glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_BRICK]);
leftWallBatch.Draw();
rightWallBatch.Draw();
3)void SpecialKeys
//设置上下键时,视坐标的z轴进行改变
{
if(key == GLUT_KEY_UP)
viewZ += 0.5f;
if(key == GLUT_KEY_DOWN)
viewZ -= 0.5f;
// Refresh the Window
glutPostRedisplay();
}
4)void ProcessMenu(int value) //创建菜单的回调函数
GLint iLoop;
//循环依次绑定纹理单元标识符,右键出现菜单栏后选择不同的菜单后,设置不同的过滤方式。
for(iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
{
glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
switch(value)
{
case 0:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
break;
case 1:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
break;
case 2:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
break;
case 3:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_LINEAR);
break;
case 4:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
break;
case 5:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
break;
}
// Trigger Redraw
glutPostRedisplay();
}
二、小结
此源码示例,与上一个纹理的示例不同点再与在SetupRC一次性设置,使用一个循环一对一一次绑定纹理标识并读取和载入纹理数据,并且生成了Mip贴图层。添加了一个菜单栏,右键鼠标后出现单击选择不同的栏,可以选择不同的过滤方式,再刷新渲染。