OpenGL入门教程(2)

// Primitieves.cpp
// OpenGL SuperBible, Chapter 2
// Demonstrates the 7 Geometric Primitives
// Program by Richard S. Wright Jr.

#include   // OpenGL toolkit
#include
#include
#include
#include
#include

#include
#ifdef __APPLE__
#include
#else
#define FREEGLUT_STATIC
#include
#endif

/////////////////////////////////////////////////////////////////////////////////
// An assortment of needed classes
GLShaderManager     shaderManager;
GLMatrixStack       modelViewMatrix;
GLMatrixStack       projectionMatrix;
GLFrame             cameraFrame;
GLFrame             objectFrame;
GLFrustum           viewFrustum;

GLBatch             pointBatch;
GLBatch             lineBatch;
GLBatch             lineStripBatch;
GLBatch             lineLoopBatch;
GLBatch             triangleBatch;
GLBatch             triangleStripBatch;
GLBatch             triangleFanBatch;

GLGeometryTransform transformPipeline;
M3DMatrix44f        shadowMatrix;

GLfloat vGreen[] = { 0.0f, 1.0f, 0.0f, 1.0f };
GLfloat vBlack[] = { 0.0f, 0.0f, 0.0f, 1.0f };

// Keep track of effects step
int nStep = 0;

///////////////////////////////////////////////////////////////////////////////
// This function does any needed initialization on the rendering context.
// This is the first opportunity to do any OpenGL related tasks.
void SetupRC()
{
// 设置背景色，刷新后生效
glClearColor(0.7f, 0.7f, 0.7f, 1.0f);

shaderManager.InitializeStockShaders();//使用存储着色器必须先初始化

glEnable(GL_DEPTH_TEST);//启动深度测试 -- 绘制z值最小的像素点
//  设置变换管transformPipeline线的矩阵堆栈        试图模型矩阵      投影矩阵  管线可以理解为一些列操作的集合
.SetMatrixStacks(modelViewMatrix, projectionMatrix);//2个矩阵对象也管线产生关联绑定

// GLFrame--帧  就是一张图片，一个照片，所以是照相机对象
cameraFrame.MoveForward(-10.0f);//移动相机,观察点不便，将相机向远处(后面)移动

//////////////////////////////////////////////////////////////////////
// Some points, more or less in the shape of Florida
GLfloat vCoast[24][3] = { { 2.80, 1.20, 0.0 }, { 2.0, 1.20, 0.0 },
{ 2.0, 1.08, 0.0 }, { 2.0, 1.08, 0.0 },
{ 0.0, 0.80, 0.0 }, { -.32, 0.40, 0.0 },
{ -0.48, 0.2, 0.0 }, { -.40, 0.0, 0.0 },
{ -0.60, -.40, 0.0 }, { -.80, -.80, 0.0 },
{ -0.80, -1.4, 0.0 }, { -.40, -1.60, 0.0 },
{ 0.0, -1.20, 0.0 }, { .2, -.80, 0.0 },
{ 0.48, -.40, 0.0 }, { .52, -.20, 0.0 },
{ 0.48, 0.20, 0.0 }, { .80, .40, 0.0 },
{ 1.20, 0.80, 0.0 }, { 1.60, 0.60, 0.0 },
{ 2.0, .60, 0.0 }, { 2.2,0.80, 0.0 },
{ 2.40, 1.0, 0.0 }, { 2.80, 1.0, 0.0 } };

//这里是为绘制的一批顶点绘图对象赋值,可以理解为绘制好了一个自定义的空间
//放到了工具箱(缓冲),等需要的时候在放到场景(窗口)中
//为顶点光栅化变量赋值,用于将顶点光栅化
// Load point batch
pointBatch.Begin(GL_POINTS, 24);
pointBatch.CopyVertexData3f(vCoast);
pointBatch.End();

// Load as a bunch of line segments
lineBatch.Begin(GL_LINES, 24);
lineBatch.CopyVertexData3f(vCoast);
lineBatch.End();

// Load as a single line segment
lineStripBatch.Begin(GL_LINE_STRIP, 24);
lineStripBatch.CopyVertexData3f(vCoast);
lineStripBatch.End();

// Single line, connect first and last points
lineLoopBatch.Begin(GL_LINE_LOOP, 24);
lineLoopBatch.CopyVertexData3f(vCoast);
lineLoopBatch.End();

// For Triangles 三角形, we'll make a Pyramid 金字塔
GLfloat vPyramid[12][3] = { -2.0f, 0.0f, -2.0f,
2.0f, 0.0f, -2.0f,
0.0f, 4.0f, 0.0f,

2.0f, 0.0f, -2.0f,
2.0f, 0.0f, 2.0f,
0.0f, 4.0f, 0.0f,

2.0f, 0.0f, 2.0f,
-2.0f, 0.0f, 2.0f,
0.0f, 4.0f, 0.0f,

-2.0f, 0.0f, 2.0f,
-2.0f, 0.0f, -2.0f,
0.0f, 4.0f, 0.0f };

triangleBatch.Begin(GL_TRIANGLES, 12);
triangleBatch.CopyVertexData3f(vPyramid);
triangleBatch.End();

// For a Triangle fan, just a 6 sided hex. Raise the center up a bit
GLfloat vPoints[100][3];    // Scratch array, more than we need
int nVerts = 0;
GLfloat r = 3.0f;
vPoints[nVerts][0] = 0.0f;
vPoints[nVerts][1] = 0.0f;
vPoints[nVerts][2] = 0.0f;
//如果需要绘制特定几何图形的话，得首先绘制特定几何图形的顶点,
//顶点如何绘制呢，就需要相应的数学知识绘制出来即可
for (GLfloat angle = 0; angle < M3D_2PI; angle += M3D_2PI / 6.0f) {
nVerts++;
vPoints[nVerts][0] = float(cos(angle)) * r;
vPoints[nVerts][1] = float(sin(angle)) * r;
vPoints[nVerts][2] = -1.5f;
}

// Close the fan
nVerts++;
vPoints[nVerts][0] = r;
vPoints[nVerts][1] = 0;
vPoints[nVerts][2] = 0.0f;

// Load it up
triangleFanBatch.Begin(GL_TRIANGLE_FAN, 8);
triangleFanBatch.CopyVertexData3f(vPoints);
triangleFanBatch.End();

// For triangle strips, a little ring or cylinder segment
int iCounter = 0;
GLfloat radius = 3.0f;
for (GLfloat angle = 0.0f; angle <= (2.0f*M3D_PI); angle += 0.3f)
{
GLfloat x = radius * sin(angle);
GLfloat y = radius * cos(angle);

// Specify the point and move the Z value up a little
vPoints[iCounter][0] = x;
vPoints[iCounter][1] = y;
vPoints[iCounter][2] = -0.5;//物体模型本身顶点向后
iCounter++;

vPoints[iCounter][0] = x;
vPoints[iCounter][1] = y;
vPoints[iCounter][2] = 0.5;//物体模型本身顶点向前
iCounter++;
}

// Close up the loop
vPoints[iCounter][0] = vPoints[0][0];
vPoints[iCounter][1] = vPoints[0][1];
vPoints[iCounter][2] = -0.5;
iCounter++;

vPoints[iCounter][0] = vPoints[1][0];
vPoi
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nts[iCounter][1] = vPoints[1][1];
vPoints[iCounter][2] = 0.5;
iCounter++;

// Load the triangle strip
triangleStripBatch.Begin(GL_TRIANGLE_STRIP, iCounter);
triangleStripBatch.CopyVertexData3f(vPoints);
triangleStripBatch.End();
}

/////////////////////////////////////////////////////////////////////////
void DrawWireFramedBatch(GLBatch* pBatch)
{
// Draw the batch solid green
shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vGreen);
pBatch->Draw();

// Draw black outline
glPolygonOffset(-1.0f, -1.0f);      // Shift depth values
glEnable(GL_POLYGON_OFFSET_LINE);

// Draw lines antialiased
glEnable(GL_LINE_SMOOTH);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

// Draw black wireframe version of geometry
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glLineWidth(2.5f);
shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vBlack);
pBatch->Draw();

// Put everything back the way we found it
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glDisable(GL_POLYGON_OFFSET_LINE);
glLineWidth(1.0f);
glDisable(GL_BLEND);
glDisable(GL_LINE_SMOOTH);
}

///////////////////////////////////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
{
// 函数原型:
// 	void glClear(GLbitfield mask);
// 参数说明：
// GLbitfield：可以使用 | 运算符组合不同的缓冲标志位，表明需要清除的缓冲，
// 	例如glClear（GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT）
// 		表示要清除颜色缓冲以及深度缓冲，可以使用以下标志位
// GL_COLOR_BUFFER_BIT : 当前可写的颜色缓冲
// GL_DEPTH_BUFFER_BIT : 深度缓冲
// GL_ACCUM_BUFFER_BIT : 累积缓冲
// GL_STENCIL_BUFFER_BIT : 模板缓冲
// 函数说明：
// glClear（）函数的作用是用当前缓冲区清除值，也就是glClearColor或者glClearDepth、
// 	glClearIndex、glClearStencil、glClearAccum等函数所指定的值来清除指定的缓冲区，
// 		也可以使用glDrawBuffer一次清除多个颜色缓存。比如：
// glClearColor（0.0，0.0，0.0，0.0）;
// glClear（GL_COLOR_BUFFER_BIT）;
// 第一条语句表示清除颜色设为黑色，第二条语句表示实际完成了把整个窗口清除为黑色的任务，
// glClear（）的唯一参数表示需要被清除的缓冲区。
// 像素检验、裁剪检验、抖动和缓存的写屏蔽都会影响glClear的操作，其中，裁剪范围限制了清除的区域，
// 而glClear命令还会忽略alpha函数、融合函数、逻辑操作、模板、纹理映射和z缓存；
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

//  glTranslatef(1, 0, 0);//向右移动(1,0,0)
//  glPushMatrix();//保存当前位置
//  glTranslatef(0, 1, 0);//如今是(1,1,0)了
//  glPopMatrix();//这样，如今又回到(1,0,0)了
modelViewMatrix.PushMatrix();
M3DMatrix44f mCamera;
cameraFrame.GetCameraMatrix(mCamera);
modelViewMatrix.MultMatrix(mCamera);

M3DMatrix44f mObjectFrame;
objectFrame.GetMatrix(mObjectFrame);//GLFrame objecctFrame关联mObjectFrame，
modelViewMatrix.MultMatrix(mObjectFrame);//modelViewMatrix关联mObjectFrame即modelViewMatrix关联objectFrame

shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vBlack);

switch (nStep) {
case 0:
glPointSize(4.0f);
pointBatch.Draw();
glPointSize(1.0f);
break;
case 1:
glLineWidth(2.0f);
lineBatch.Draw();
glLineWidth(1.0f);
break;
case 2:
glLineWidth(2.0f);
lineStripBatch.Draw();
glLineWidth(1.0f);
break;
case 3:
glLineWidth(2.0f);
lineLoopBatch.Draw();
glLineWidth(1.0f);
break;
case 4:
DrawWireFramedBatch(&triangleBatch);
break;
case 5:
DrawWireFramedBatch(&triangleStripBatch);
break;
case 6:
DrawWireFramedBatch(&triangleFanBatch);
break;
}

modelViewMatrix.PopMatrix();

// Flush drawing commands
glutSwapBuffers();
}

// Respond to arrow keys by moving the camera frame of reference
void SpecialKeys(int key, int x, int y)
{
if (key == GLUT_KEY_UP)
objectFrame.RotateWorld(m3dDegToRad(-5.0f), 1.0f, 0.0f, 0.0f);

if (key == GLUT_KEY_DOWN)
objectFrame.RotateWorld(m3dDegToRad(5.0f), 1.0f, 0.0f, 0.0f);

if (key == GLUT_KEY_LEFT)
objectFrame.RotateWorld(m3dDegToRad(-5.0f), 0.0f, 1.0f, 0.0f);

if (key == GLUT_KEY_RIGHT)
objectFrame.RotateWorld(m3dDegToRad(5.0f), 0.0f, 1.0f, 0.0f);

glutPostRedisplay();
}

///////////////////////////////////////////////////////////////////////////////
// A normal ASCII key has been pressed.
// In this case, advance the scene when the space bar is pressed
void KeyPressFunc(unsigned char key, int x, int y)
{
if (key == 32)
{
nStep++;

if (nStep > 6)
nStep = 0;
}

switch (nStep)
{
case 0:
glutSetWindowTitle("GL_POINTS");
break;
case 1:
glutSetWindowTitle("GL_LINES");
break;
case 2:
glutSetWindowTitle("GL_LINE_STRIP");
break;
case 3:
glutSetWindowTitle("GL_LINE_LOOP");
break;
case 4:
glutSetWindowTitle("GL_TRIANGLES");
break;
case 5:
glutSetWindowTitle("GL_TRIANGLE_STRIP");
break;
case 6:
glutSetWindowTitle("GL_TRIANGLE_FAN");
break;
}

glutPostRedisplay();
}

///////////////////////////////////////////////////////////////////////////////
// Window has changed size, or has just been created. In either case, we need
// to use the window dimensions to set the viewport and the projection matrix.
void ChangeSize(int w, int h)
{
glViewport(0, 0, w, h);
// 	计算截锥体的角，并设置投影矩阵。
// 	透视投影矩阵
// 	设置为3D投影模式
viewFrustum.SetPerspective(45.0f, float(w) / float(h), 1.0f, 500.0f);
projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
// 	Description描述
// 		加载一个单位矩阵到当前的模型视图矩阵。
// 		改变模型视图矩阵会覆盖当前的camera' 的参数，许多情况下你需要用到GL.PushMatrix 和GL.PopMatrix矩阵函数.来保存和恢复。
modelViewMatrix.LoadIdentity();
}

///////////////////////////////////////////////////////////////////////////////
// Main entry point for GLUT based programs
int main(int argc, char* argv[])
{
gltSetWorkingDirectory(argv[0]);

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
glutInitWindowSize(800, 600);
glutCreateWindow("GL_POINTS");
glutReshapeFunc(ChangeSize);//相当于MFC里面的OnSize
glutKeyboardFunc(KeyPressFunc);//相当于MFC里面的键盘接受事件消息
glutSpecialFunc(SpecialKeys);//相当于MFC里面的特定键盘接受事件消息 上下左右
glutDisplayFunc(RenderScene);//相当于MFC里面的OnRepint()回调函数，相当于Cocos2d-x里面的update

GLenum err = glewInit();
if (GLEW_OK != err) {
fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
return 1;
}

SetupRC();

glutMainLoop();
return 0;
}