如何使用GLUT在按键上绘制形状?
问题描述:
我想按空格键时画一个圆柱体。如何使用GLUT在按键上绘制形状?
这是代码的摘录我现在所拥有的:
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;
}
然而,当我按下空格键,气缸不绘制。我不知道该怎么做。当我复制我在processKeys方法中的代码并将其粘贴到显示器方法中时,它工作正常。 我该怎么做?
答
如函数名称所示,使用display
函数绘制对象。因此,为了实现你想要的,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();
}
+0
谢谢,但我只能使用这种方法绘制一个柱面。我怎样才能创建一个全新的每一个按键? – OldMcDonald
+1
你可以使用一个变换矢量,所以在每次按下之后,向这个矢量和绘图函数添加一个新的变换,你只需要对它进行修改 – Amadeus
我不认为你被允许从任何地方绘制,但显示功能。 – HolyBlackCat