opengl超级宝典（第五版）阅读笔记 2

加入了按键来控制方块的移动，通过改变方块的位置然后刷新屏幕来实现，基本原理其实也很简单。
前面已经注释过的这里可能没有进一步注释了 。

#include <GLTools.h>	// OpenGL toolkit
#include <GLShaderManager.h>
#define FREEGLUT_STATIC  //在windows和linux上，使用freeglut静态版本，需要添加这一行，否则会出现错误
#include <glut.h>
#pragma comment(lib,"gltools.lib")//要加上这一行链接一下gltools库
GLShaderManager shaderManager;//着色器管理器 
GLBatch squareBatch;//用来绘制基本的方形图元
GLfloat blockSize = 0.1f;//方块的大小
GLfloat vVerts[] = { -blockSize, -blockSize, 0.0f,
blockSize, -blockSize, 0.0f,
blockSize,  blockSize, 0.0f,
-blockSize,  blockSize, 0.0f };//设置方块的四个坐标点

void SetupRC()
{
	glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
	shaderManager.InitializeStockShaders();
	// Load up a triangle  
	squareBatch.Begin(GL_TRIANGLE_FAN, 4);
	squareBatch.CopyVertexData3f(vVerts);
	squareBatch.End();
}

void SpecialKeys(int key, int x, int y)
{
	GLfloat stepSize = 0.025f;//每次移动的步长
	GLfloat blockX = vVerts[0];   // 方形左边的x坐标
	GLfloat blockY = vVerts[7];  // 方形上边的y坐标

	if (key == GLUT_KEY_UP)
		blockY += stepSize;

	if (key == GLUT_KEY_DOWN)
		blockY -= stepSize;

	if (key == GLUT_KEY_LEFT)
		blockX -= stepSize;

	if (key == GLUT_KEY_RIGHT)
		blockX += stepSize;

	// Collision detection   
	if (blockX < -1.0f) blockX = -1.0f;//x小于左边界，x不能继续移动，保持原位
	if (blockX >(1.0f - blockSize * 2)) blockX = 1.0f - blockSize * 2;//根据坐标关系，方形边长为2*blockSize，这样可以保证右边界不越界
	if (blockY < -1.0f + blockSize * 2)  blockY = -1.0f + blockSize * 2;//保证左边界不越界
	if (blockY > 1.0f) blockY = 1.0f;//y大于上边界，保持原位

	// Recalculate vertex positions   
	vVerts[0] = blockX;
	vVerts[1] = blockY - blockSize * 2;

	vVerts[3] = blockX + blockSize * 2;
	vVerts[4] = blockY - blockSize * 2;

	vVerts[6] = blockX + blockSize * 2;
	vVerts[7] = blockY;

	vVerts[9] = blockX;
	vVerts[10] = blockY;

	squareBatch.CopyVertexData3f(vVerts);

	glutPostRedisplay();//刷新屏幕
}

void RenderScene(void)
{
	// Clear the window with current clearing color   
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

	GLfloat vRed[] = { 1.0f, 0.0f, 0.0f, 1.0f };
	shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vRed);
	squareBatch.Draw();

	// Flush drawing commands   
	glutSwapBuffers();
}

void ChangeSize(int w, int h)
{
	glViewport(0, 0, w, h);
}

int main(int argc, char* argv[])
{
	gltSetWorkingDirectory(argv[0]);
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
	glutInitWindowSize(800, 600);
	glutCreateWindow("Move Block with Arrow Keys");
	GLenum err = glewInit();
	if (GLEW_OK != err)
	{
		// Problem: glewInit failed, something is seriously wrong.   
		fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
		return 1;
	}
	glutReshapeFunc(ChangeSize);
	glutDisplayFunc(RenderScene);
	glutSpecialFunc(SpecialKeys);//注册按键消息

	SetupRC();

	glutMainLoop();
	return 0;
}