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《高效学习OpenGL》 之 控制光源的位置和方向

1.如何使光源保持静止

在使用完视图和模型变换之前设置光源的位置,init()的后面, display()之前


2.独立的移动光源

在模型变换之后设置光源位置

#include <GL/glut.h>
#include <stdlib.h>

static int spin = 0;

void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel (GL_SMOOTH);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
}

void display(void)
{
GLfloat position[] = { 0.0, 0.0, 1.5, 1.0 };

glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix ();//用于隔离视图变换和模型变换
gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

glPushMatrix ();//用于隔离视图变换和模型变换
glRotated ((GLdouble) spin, 1.0, 0.0, 0.0);//旋转光源
glLightfv (GL_LIGHT0, GL_POSITION, position);

glTranslated (0.0, 0.0, 1.5);
glDisable (GL_LIGHTING);
glColor3f (0.0, 1.0, 1.0);
glutWireCube (0.1);
glEnable (GL_LIGHTING);
glPopMatrix ();//局部坐标系归位
glutSolidTorus (0.25, 0.85, 8, 15);
glPopMatrix ();
glFlush ();
}

void reshape (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

void mouse(int button, int state, int x, int y)
{
switch (button) {
case GLUT_LEFT_BUTTON:
if (state == GLUT_DOWN) {
spin = (spin + 30) % 360;
glutPostRedisplay();
}
break;
default:
break;
}
}

void keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
}
}

int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize (500, 500);
glutInitWindowPosition (100, 100);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}


3.光源和观测点一起移动


void display(void)
{
GLfloat position[] = { 0.0, 0.0, 1.5, 1.0 };

glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix ();
gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

//glPushMatrix ();
glRotated ((GLdouble) spin, 1.0, 0.0, 0.0);
glLightfv (GL_LIGHT0, GL_POSITION, position);

glTranslated (0.0, 0.0, 1.5);
glDisable (GL_LIGHTING);
glColor3f (0.0, 1.0, 1.0);
glutWireCube (0.1);
glEnable (GL_LIGHTING);
//glPopMatrix ();
glTranslated (0.0, 0.0, 1.5);//增加的代码

glutSolidTorus (0.275, 0.85, 8, 15);
glPopMatrix ();
glFlush ();
}




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