OpenGL蓝宝书第五章代码勘误以及惯性坐标系去解释模型变换

如果你也发现按照教程代码完成贴图时，你会底面的坐标和平常顶点坐标正负相反，比如-1.0f, -1.0f, -1.0f这个顶点对应的却是世界坐标中1.0f,-1.0f,1.0f

问题究竟出现在哪里？

原来是：objectFrame.GetCameraMatrix(mObjectFrame); //原书中的代码为GetMatrix，获取了objectFrame的朝向，导致顶点和纹理的对象关系出现了相反内容

objectFrame中的朝向和OpenGL的默认朝向相反，getMatrix的操作会导致modelViewMatrix在无形中执行了一次180°旋转。鉴于此，我们应该只需要获得其camera矩阵即可。这个camera矩阵记录了当前模型的旋转、缩放和位移。modelViewMatrix乘上这个矩阵的结果就是世界原点到模型各顶点的作用矩阵。

这里引出一个我差点忘记的概念：惯性坐标。

世界坐标系的原点通过变换矩阵，可定位了模型的位移、旋转（包含朝向和定义惯性正方向）、缩放状态（这个其实对世界顶点变换影响不大，只是模型对于自身的惯性相对点影响比较大）。实际渲染绘制流程是：世界原点，移动画刷（这个概念很重要），旋转画刷，根据缩放绘制模型各顶点。模型各顶点的位置是相对于画刷的，画刷其实在更多情况下命名为模型的惯性坐标系。从世界坐标系到画刷（模型惯性坐标系）则是模型变换矩阵，模型顶点的绘制则由模型编辑器或绘制算法定义。摄像机则影响了最终可视区域。有些情况下，模型惯性坐标系的原点是摄像机的当前所在位置。

如果代码中使用了

//modelViewMatrix.Translate(0.0f, -1.0f, -7.0f);

这样类似的操作，而不是从camera中获取相对位移矩阵，那么这个模型的惯性坐标系是相对于世界坐标空间的原点。

由此，纹理贴图的st对应关系环绕就清楚的和2D像素点操作明显区别开来。

OpenGL的st从左下角为原点，而内存中的像素操作是从左上角为原点。

#include <GLTools.h>
#include <GLMatrixStack.h>
#include <GLGeometryTransform.h>
#include <GLFrustum.h>
#include <GLFrame.h>
#include <GLShaderManager.h>
#include <iostream>

#include <math.h>

#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endif

GLMatrixStack mvpMatrix;
GLMatrixStack projectionMatrix;
GLMatrixStack modelViewMatrix;

GLFrustum viewFrustum;
GLGeometryTransform transformPipeLine;

GLFrame cameraFrame;
GLFrame objectFrame;

GLBatch pyramidBatch;
GLuint textureID;
GLShaderManager shaderManager;

void ChangeSize(int w, int h)
{
	if (h <= 0)
	{
		h = 1;
	}

	glViewport(0, 0, w, h);
	viewFrustum.SetPerspective(35, float(w) / float(h), 1.0f, 1000.0f);
	projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
	transformPipeLine.SetMatrixStacks(modelViewMatrix, projectionMatrix);
}

// Load a TGA as a 2D Texture. Completely initialize the state
bool LoadTGATexture(const char *szFileName, GLenum minFilter, GLenum magFilter, GLenum wrapMode)
{
	GLbyte *pBits;
	int nWidth, nHeight, nComponents;
	GLenum eFormat;

	// Read the texture bits
	pBits = gltReadTGABits(szFileName, &nWidth, &nHeight, &nComponents, &eFormat);
	if (pBits == NULL)
		return false;

	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapMode);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapMode);

	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);

	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glTexImage2D(GL_TEXTURE_2D, 0, nComponents, nWidth, nHeight, 0,
		eFormat, GL_UNSIGNED_BYTE, pBits);

	free(pBits);

	if (minFilter == GL_LINEAR_MIPMAP_LINEAR ||
		minFilter == GL_LINEAR_MIPMAP_NEAREST ||
		minFilter == GL_NEAREST_MIPMAP_LINEAR ||
		minFilter == GL_NEAREST_MIPMAP_NEAREST)
		glGenerateMipmap(GL_TEXTURE_2D);

	return true;
}

void MakePyramid(GLBatch & pyramidBatch)
{
	//每三个点画一个三角形
	pyramidBatch.Begin(GL_TRIANGLES, 18, 1);

	//原点在金字塔的几何中心（总之就是非重点，比中心高的的位置，高度的1/2）

	//底部,初始法线是向下,纹理映射的顶点需要查看原始纹理对照一下？？ //todo
	//逆着法线看的话，下面三个点的环绕是逆时针的
	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	pyramidBatch.Vertex3f(-1.0f, -1.0f, -1.0f);

	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
	pyramidBatch.Vertex3f(1.0f, -1.0f, -1.0f);

	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
	pyramidBatch.Vertex3f(1.0f, -1.0f, 1.0f);

	//逆着法线看的话，下面三个点的环绕是逆时针的
	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
	pyramidBatch.Vertex3f(-1.0f, -1.0f, 1.0f);

	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	pyramidBatch.Vertex3f(-1.0f, -1.0f, -1.0f);

	pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
	pyramidBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
	pyramidBatch.Vertex3f(1.0f, -1.0f, 1.0f);

	//原先作者代码中的front和back的方向不是相对于观察者所得到的视野
	//“前”这个面竟然是金字塔的背对着我们的面，即第一视角看不到这个面
	//感觉这坐标竟然是

	M3DVector3f vApex = { 0.0f, 1.0f, 0.0f };
	M3DVector3f vFrontLeft = { -1.0f, -1.0f, 1.0f };
	M3DVector3f vFrontRight = { 1.0f, -1.0f, 1.0f };
	M3DVector3f vBackLeft = { -1.0f, -1.0f, -1.0f };
	M3DVector3f vBackRight = { 1.0f, -1.0f, -1.0f };

	M3DVector3f n;

	//求法线,前
	m3dFindNormal(n, vApex, vFrontLeft, vFrontRight);
	pyramidBatch.Normal3fv(n);
	pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
	pyramidBatch.Vertex3fv(vApex);

	pyramidBatch.Normal3fv(n);
	pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	pyramidBatch.Vertex3fv(vFrontLeft);

	pyramidBatch.Normal3fv(n);
	pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
	pyramidBatch.Vertex3fv(vFrontRight);

	////求法线，左
	//m3dFindNormal(n, vApex, vBackLeft, vFrontLeft);
	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
	//pyramidBatch.Vertex3fv(vApex);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vBackLeft);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vFrontLeft);

	////求法线，右
	//m3dFindNormal(n, vApex, vFrontRight, vBackRight);
	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
	//pyramidBatch.Vertex3fv(vApex);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vFrontRight);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vBackRight);

	////求法线，后
	//m3dFindNormal(n, vApex, vBackRight, vBackLeft);
	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
	//pyramidBatch.Vertex3fv(vApex);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vBackRight);

	//pyramidBatch.Normal3fv(n);
	//pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
	//pyramidBatch.Vertex3fv(vBackLeft);

	pyramidBatch.End();
}

void SetupRC(void)
{
	glClearColor(0.7f, 0.7f, 0.7f, 1.0f);

	shaderManager.InitializeStockShaders();

	glEnable(GL_DEPTH_TEST);

	glGenTextures(1, &textureID);
	glBindTexture(GL_TEXTURE_2D, textureID);
	LoadTGATexture("stone.tga", GL_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE);
	MakePyramid(pyramidBatch);

	cameraFrame.MoveForward(-7.0f);//？？什么用意？？
}

void RenderScene(void)
{
	static GLfloat vLightPos[] = { 1.0f, 1.0f, 0.f };
	static GLfloat vWhite[] = { 1.0f, 1.0f, 1.0f, 1.0f };

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

	modelViewMatrix.PushMatrix();
	//{
		//处理画笔位置相关，即模型相对于摄像机的位置

		M3DMatrix44f mCamera;
		cameraFrame.GetCameraMatrix(mCamera);
		modelViewMatrix.MultMatrix(mCamera);
		//modelViewMatrix.Translate(0.0f, -1.0f, -7.0f);

		//处理模型自身的旋转或缩放
		M3DMatrix44f mObjectFrame;
		objectFrame.GetCameraMatrix(mObjectFrame); //原书中的代码为GetMatrix，获取了objectFrame的朝向，导致顶点和纹理的对象关系出现了相反内容
		modelViewMatrix.MultMatrix(mObjectFrame);

		glBindTexture(GL_TEXTURE_2D, textureID);
		shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF,
			transformPipeLine.GetModelViewMatrix(),
			transformPipeLine.GetProjectionMatrix(),
			vLightPos, vWhite, 0);
		pyramidBatch.Draw();
	//}
	modelViewMatrix.PopMatrix();

	glutSwapBuffers();
}

void ShutdownRC(void)
{
	glDeleteTextures(1, &textureID);
}

void SpecialKeys(int key, int x, int y)
{
	if (key == GLUT_KEY_UP)
	{
		objectFrame.RotateWorld(m3dDegToRad(5.0f),1.0f,0.0f,0.0f);//模型和摄像机的操作是相反的，模型向上旋转5.0f
	}

	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();
}

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("Pyramid");
	glutReshapeFunc(ChangeSize);
	glutSpecialFunc(SpecialKeys);
	glutDisplayFunc(RenderScene);

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

	SetupRC();

	glutMainLoop();

	ShutdownRC();

	return 0;
}

版权声明：本文为博主原创文章，未经博主允许不得转载。

时间： 2024-08-28 07:56:44

OpenGL蓝宝书第五章代码勘误以及惯性坐标系去解释模型变换的相关文章

OpenGL蓝宝书第五章5.4Tunnuel 纹理映射和过滤：较好的可读性代码

主要处理了纹理贴图和顶点映射的关系.根据法线先确认环绕方向.然后根据绘制的primitive_type完成纹理顶点直接的映射. 哪里来,哪里回:根据法线来确认逆时针方向.strip的画法要熟悉,从其实的两个顶点开始已折线的形式前进 GL_TRIANGLES_STRIP是常用的绘制方式,在循环代码中使用四个顶点+循环控制量能完成大量的几何图形绘制.这里我犯了个错误,没意识到折线的的前进方向问题,导致纹理映射出现了偏差,一度去怀疑modelViewMatrix的配置是否正确.但是我发现原书中的代码没

OpenGL蓝宝书第六章代码疑虑：为什么使用了GL_TEXTURE_1D??纹理和顶点间的映射是如何实现？

遇到一个大问题,明明加载纹理绑定的是GL_TEXTURE_2D glUniform1i(locCloudTex, 1); //明明默认为0,参数却不是0. 可是原书中代码确是 glGenTextures(1, &uiTexture); glBindTexture(GL_TEXTURE_1D, uiTexture); // LoadTGATexture("Clouds.tga", GL_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE); glUniform

OpenGL蓝宝书第七章：立体天空和纹理折射、双纹理（下）

对比了蓝宝书,才知道红宝书的优点. reflect函数的原理在红宝书中有说明,只有对比了红宝书,才知道红宝书的定位:高级工具书. 蓝宝书作为入门级书籍,以较快的速度让读者敲到代码去思考,总遗留了需要探索的内容. 蓝宝书要看完. 红宝书要看完. C++11 标准版英文版也看了小部分. 多线程入门都不算. Socket只能实现基础网络连接,离真正的数据通信都算,何况多人在线对战网络模型的实现 设计模式看了又忘了,忘了又看,如果没有机会去设计模块级别的代码实现,真的血了没用,难道改UI?加班赶工哪有魄

6.12白书第五章图论总结——司雨寒

之前我的图论一直都是DFS一下,BFS一下,求个欧拉回路,拓扑排个序这种渣渣水平. 终于鼓起勇气拾起白书第五章的东西. 学(bei)习(song)了一下求双连通分量,二分图的判定,强连通分量,2-SAT. DFS加上时间戳这个东西,很强大. 最后刷了白书上的例题: BCC: LA3523 可以参加会议的是双联通分量上的奇圈 1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 #include

第五章 代码重用与函数编写（1）

****************************** 第五章 代码重用与函数编写 ********************************* 代码重用的好处:使用require()和include()函数:函数介绍:定义函数:使用参数:理解作用域: 返回值:参数的引用调用和值调用:实现递归:使用命名空间 *************** 5.1 代码重用的好处 1.成本低:2.可靠性:3.一致性:系统的外部接口是一致的,其中包括用户接口和系统的外部接口. *************

lrj紫书第五章

UVA-1592 1 // UVa1592 Database 2 // Rujia Liu 3 // 本程序只是为了演示STL各种用法,效率较低.实践中一般用C字符串和哈希表来实现. 4 5 #include<iostream> 6 #include<cstdio> 7 #include<vector> 8 #include<string> 9 #include<map> 10 #include<sstream> 11 using n

紫书第五章训练3 D - Throwing cards away I

D - Throwing cards away I Given is an ordered deck of n cards numbered 1 to n with card 1 at the top and card n at the bottom. The following operation is performed as long as there are at least two cards in the deck: Throw away the top card and move

紫书第五章训练2 F - Compound Words

F - Compound Words You are to find all the two-word compound words in a dictionary. A two-word compound word is a word in the dictionary that is the concatenation of exactly two other words in the dictionary. Input Standard input consists of a number

紫书第五章训练 uva 10763 Foreign Exchange by crq

Your non-profit organization (iCORE - international Confederation of Revolver Enthusiasts) coordinates a very successful foreign student exchange program. Over the last few years, demand has sky-rocketed and now you need assistance with your task.The