openGL——03、三维透视投影

需求

使用三维透视投影实现下面的透视效果：

透视投影.png

原理

在三维空间的xy平面上画螺旋线，再用透视投影的方法投影到与xy平面不平行的平面上。

代码

/**
* @date: 2017.06.05
*/

#include <GL/glut.h>

GLfloat winWidth = 600, winHeight = 600;

GLfloat x0 = 100, y0 = 50, z0 = 50;
GLfloat xref = 50, yref = 50, zref = 0.0;
GLfloat Vx = 0.0, Vy = 1.0, Vz = 0.0;

GLfloat xwMin = -40, ywMin =-60, xwMax = 40, ywMax = 60;

GLfloat dnear = 25.0, dfar = 125.0;

void init(void) {
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glMatrixMode(GL_MODELVIEW);
    gluLookAt(x0, y0, z0, xref, yref, zref, Vx, Vy, Vz);

    glMatrixMode(GL_PROJECTION);
    glFrustum(xwMin, xwMax, ywMin, ywMax, dnear, dfar);
}

void displayFcn(void) {
    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(0.0, 1.0, 0.0);
    glPolygonMode(GL_FRONT, GL_FILL);
    glPolygonMode(GL_BACK, GL_LINE);
    glBegin(GL_QUADS);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(100.0, 0.0, 0.0);
    glVertex3f(100.0, 100.0, 0.0);
    glVertex3f(0.0, 100.0, 0.0);
    glEnd();
    
    glFlush();
}

void reshapeFcn(GLint newWidth, GLint newHeight) {
    glViewport(0, 0, newWidth, newHeight);
    winWidth = newHeight;
    winHeight = newHeight;
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowPosition(50, 50);
    glutInitWindowSize(winWidth, winHeight);
    glutCreateWindow("perspectiver View of A Square");

    init();
    glutDisplayFunc(displayFcn);
    glutReshapeFunc(reshapeFcn);

    glutMainLoop();

}

githup链接：
https://github.com/lifeSo/OpenGLDemo/blob/master/01.get start/05.perspectiver view of square.c
https://github.com/lifeSo/OpenGLDemo/blob/master/01.get start/06.perspectiver view of spiral line.c