我想按空格键时画一个圆柱体。
这是我现在所拥有的代码的摘录:
void draw_cylinder(GLfloat radius,
GLfloat height,
GLubyte R,
GLubyte G,
GLubyte B)
{
GLfloat x = 0.0;
GLfloat y = 0.0;
GLfloat angle = 0.0;
GLfloat angle_stepsize = 0.1;
/** Draw the tube */
glColor3ub(R - 40, G - 40, B - 40);
glBegin(GL_QUAD_STRIP);
angle = 0.0;
while (angle < 2 * 3.141) {
x = radius * cos(angle);
y = radius * sin(angle);
glVertex3f(x, y, height);
glVertex3f(x, y, 0.0);
angle = angle + angle_stepsize;
}
glVertex3f(radius, 0.0, height);
glVertex3f(radius, 0.0, 0.0);
glEnd();
/** Draw the circle on top of cylinder */
glColor3ub(R, G, B);
glBegin(GL_POLYGON);
angle = 0.0;
while (angle < 2 * 3.141) {
x = radius * cos(angle);
y = radius * sin(angle);
glVertex3f(x, y, height);
angle = angle + angle_stepsize;
}
glVertex3f(radius, 0.0, height);
glEnd();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
}
void reshape(GLsizei width, GLsizei height) {
if (height == 0) height = 1;
GLfloat aspect = (GLfloat)width / (GLfloat)height;
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(35.0f, aspect, 0.1f, 100.0f);
}
void processKeys(unsigned char key, int x, int y) {
if (key == 32) { // space key
glLoadIdentity();
glTranslatef(0.0, -0.4, -5.0);
glRotatef(-90, 0.4, 0.0, 0.0);
draw_cylinder(0.3, 1.0, 255, 160, 100);
}
glutPostRedisplay();
}
int main(int argc, char** argv) {
glutInit(&argc, argv); // Initialize GLUT
glutInitDisplayMode(GLUT_DOUBLE); // Enable double buffered mode
glutInitWindowSize(640, 480); // Set the window's initial width & height
glutInitWindowPosition(50, 50); // Position the window's initial top-left corner
glutCreateWindow(title); // Create window with the given title
glutKeyboardFunc(processKeys);
glutDisplayFunc(display); // Register callback handler for window re-paint event
glutReshapeFunc(reshape); // Register callback handler for window re-size event
initGL(); // Our own OpenGL initialization
glutMainLoop(); // Enter the infinite event-processing loop
return 0;
}
但是,当我按空格键时,不会绘制圆柱体。我不知道该怎么做。当我复制 processKeys 方法中的代码并将其粘贴到 display 方法时,它可以正常工作。 我该怎么办呢?
答案 0 :(得分:1)
正如函数名称所示,您使用display
函数绘制对象。因此,为了实现您想要的,创建一个布尔变量(例如全局范围)并使用它来控制是否要绘制圆柱体。例如:
bool cylinder_draw = false;
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
if ( cylinder_draw ) {
glLoadIdentity();
glTranslatef(0.0, -0.4, -5.0);
glRotatef(-90, 0.4, 0.0, 0.0);
draw_cylinder(0.3, 1.0, 255, 160, 100);
}
}
void processKeys(unsigned char key, int x, int y) {
if (key == 32) { // space key
cylinder_draw = true;
}
glutPostRedisplay();
}