课程实验指导5-投影

1、.课程实验指导五实验5 投影1实验目的：了解透视图投影原理，利用vc+opengl实现立方体的一点、两点、三点透视图算法。2实验内容：（1） 理解投影原理；（2） 读懂示范代码；（3） 增加键盘控制，控制一点透视点产生正方体的移动、旋转效果；（4） 实现两点透图效果。3实验原理：本次实验内容为绘制立方体的一点透视图。透视投影按照主灭点的个数分为一点透视、二点透视和三点透视，如下图1所示。灭点灭点灭点灭点灭点灭点 图1 立方体的三类透视其中一点透视情况如图2所示，设z轴上有一观察点（即视点）v(0,0,d)，从v点出发将物体上的点p( x, y, z)投影到xoy平面上得到p (x,y,0)，由

2、相似三角形可知一点透视变换矩阵为：精品.图2 一点透视示意.(1)根据以上，可得一点透视变换的步骤如下：(1)将三维形体平移到适当位置lx、ly、lz；(2)令视点在z轴(0,0,d)，利用上述公式(1)进行透视变换；4实验代码：/ projection.cpp : defines the entry point for the console application./#include stdafx.h#include #include #include struct matrix double p44; matrix operator*(matrix &); matrix();/单位矩阵;

3、matrix:matrix() for(long i=0;i4;i+) for(long j=0;j4;j+) if(i=j) pij = 1; else pij = 0; matrix multiply(matrix& m1, matrix& m2)matrix m;for(int i=0;i4;i+)for(int j=0;j4;j+)for(int k=0;k4;k+)精品.m.pij+=(m1.pik*m2.pkj);return m;struct pt2d int x, y;pt2d()x = 0; y = 0;pt2d(int px, int py)x = px; y = py;s

4、truct pt3d float x, y, z;pt3d()x = 0; y = 0; z = 0;pt3d(float px, float py, float pz)x = px; y = py; z = pz;struct faceinfo /第一列为每个面的顶点数；其余列为面的顶点编号int num, idx1, idx2, idx3, idx4;faceinfo()num = 0; idx1 = 0; idx2 = 0;idx3 = 0; idx4 = 0;faceinfo(int fnum, int fidx1, int fidx2, int fidx3, int fidx4)nu

5、m = fnum; idx1 = fidx1; idx2 = fidx2;idx3 = fidx3;idx4 = fidx4;double lx = 480, ly = 460, lz = 240;double phi = 0;double d = -500;matrix mt, mr, mp, mtemp, ma;pt3d boxpt8;pt2d boxpt2d8;faceinfo finfo6;void initparameter()/初始化参数mt.p30 = lx; mt.p31 = ly;mt.p32 = lz;mr.p00 = cos(phi); mr.p02 = -sin(phi

6、);mr.p20 = sin(phi); mr.p22 = cos(phi);mp.p22 = 0;mp.p23 = -1/d;mtemp = multiply(mt, mr);精品.ma = multiply(mtemp, mp);void project(pt3d pt, pt2d &pt2d)/透视变换double pth4;pth0=pt.x;/pth1=pt.y;pth2=pt.z;pth3=1;double res4;for(int i=0;i4;i+)resi = 0;for(i=0;i4;i+)for(int j=0;j4;j+)resi+=(pthj*ma.pji);pt2d

7、 = pt2d(res0/res3, res1/res3);void linegl(pt2d pt0, pt2d pt1)glbegin (gl_lines);glcolor3f (1.0f, 0.0f, 0.0f); glvertex2f (pt0.x,pt0.y);glcolor3f (0.0f, 1.0f, 0.0f); glvertex2f (pt1.x,pt1.y);glend ();int getptidx(faceinfo finfo, int ptidx)int idx = 0; switch (ptidx)case 1:idx = finfo.idx1;break;case

8、2:idx = finfo.idx2;break;case 3:idx = finfo.idx3;break;精品.case 4:idx = finfo.idx4;break;default:break;return idx;void boxproject()int ptidx;pt2d pt2d;for(int face=0;face6;face+)int num=finfoface.num;/面的总边数for(int i=0;inum;i+)/边循环ptidx = getptidx(finfoface, i);/面的顶点号project(boxptptidx, pt2d);boxpt2dp

9、tidx = pt2d;void drawbox()int ptidx4;for(int face=0;face4;face+)int num =finfoface.num;/面的总顶点数for(int i=0;inum;i+)/循环ptidxi = getptidx(finfoface, i+1);/面的顶点号for(int j=0; j4; j+)int idx0 = ptidxj;int idx1 = (j= 3) ? ptidx0:ptidxj+1);linegl(boxpt2didx0, boxpt2didx1);精品.void mydisplay()glclear(gl_color

10、_buffer_bit);glcolor3f (1.0f, 0.0f, 0.0f); initparameter();boxproject();drawbox();glutswapbuffers();void init()glclearcolor(0.0, 0.0, 0.0, 0.0);glshademodel(gl_flat);printf(hello cube!n);void reshape(int w, int h)glviewport(0, 0, (glsizei) w, (glsizei) h);glmatrixmode(gl_projection);glloadidentity()

11、;gluortho2d(0.0, (gldouble) w, 0.0, (gldouble) h);void keyboard(unsigned char key, int x, int y)switch (key)case x:break;default:break;void readpoint()/读入8个顶点坐标float bl = 200;/box lengthboxpt0 = pt3d(-bl/2, -bl/2, -bl/2);精品.boxpt1 = pt3d(-bl/2, bl/2, -bl/2);boxpt2 = pt3d(-bl/2, bl/2, bl/2);boxpt3 =

12、pt3d(-bl/2, -bl/2, bl/2);boxpt4 = pt3d(bl/2, -bl/2, -bl/2);boxpt5 = pt3d(bl/2, bl/2, -bl/2);boxpt6 = pt3d(bl/2, bl/2, bl/2);boxpt7 = pt3d(bl/2, -bl/2, bl/2);void readface()/读入6个面坐标finfo0 = faceinfo(4, 0, 1, 2, 3);finfo1 = faceinfo(4, 0, 3, 7, 4);finfo2 = faceinfo(4, 4, 5, 6, 7);finfo3 = faceinfo(4, 5, 1, 2, 6);finfo4 = faceinfo(4, 7, 6, 2, 3);finfo5 = faceinfo(4, 4, 5, 1, 0);int main(int argc, char *argv)glutinit(&argc, argv);glutinitdisplaymode(glut_rgb | glut_double);glutinitwindowposition(100, 100);glutinitwindowsize(640, 480);gl