OpenGL入门教程(2)

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// 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];
	vPoints[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;
}