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:Pyramid.cpp

Posted 2020-06-24 yxwkaifa

假设你也发现依照教程代码完毕贴图时，你会底面的坐标和寻常顶点坐标正负相反，比方-1.0f, -1.0f, -1.0f这个顶点相应的却是世界坐标中1.0f,-1.0f,1.0f

问题到底出如今哪里？

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在无形中运行了一次180°旋转。鉴于此，我们应该仅仅须要获得其camera矩阵就可以。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（包括朝向和定义惯性正方向）、缩放状态（这个事实上对世界顶点变换影响不大。仅仅是模型对于自身的惯性相对点影响比較大）。

实际渲染绘制流程是：世界原点，移动画刷（这个概念非常重要），旋转画刷，依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。画刷事实上在很多其它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。

摄像机则影响了终于可视区域。

（有些情况下取用了相机的变换矩阵，模型惯性坐标系的原点是摄像机的当前所在位置）。

假设代码中使用了

//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的原点和世界坐标空间的原点，只是是运行了移动是以于自身的为原点。关注点之中的一个：惯性坐标系（画刷）的默认朝向正方向是和OpenGL的世界坐标系一样使用的是右手坐标系。

所以，-7也是向屏幕里面移动。

由此，纹理贴图的st相应关系围绕就清楚的和2D像素点操作明显差别开来。

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。

此外还遇到一个问题，使用了release的模式库，导致无法正常调试。比方代码优化导致无法断点和查看到正确的数据。仅仅能切换回debug模式。

M3DMatrix44f mCamera;
cameraFrame.GetCameraMatrix(mCamera);
modelViewMatrix.MultMatrix(mCamera);//仅仅是获取cameraFrame中记录的位移。没有获得朝向和旋转

#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,纹理映射的顶点须要查看原始纹理对比一下？？ //todo
	//逆着法线看的话。以下三个点的围绕是逆时针的
	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，以下三个点的围绕是逆时针的
	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”这个面居然是金字塔的背对着我们的面，即第一视角看不到这个面
	//感觉这坐标居然是

	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);//仅仅是获取cameraFrame中记录的位移，没有获得朝向和旋转
		//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;
}