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#include <math.h>
#include <GL/gl.h>
#include <GL/glut.h>
struct {
float triangle_rotation;
} scene;
static const GLfloat triangle_vertices[3][3] = {
{-1., -1., 0.},
{ 1., -1., 0.},
{ 0., 0.732, 0.}
};
static void draw_triangle()
{
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 3*sizeof(GLfloat), &triangle_vertices[0][0]);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableClientState(GL_VERTEX_ARRAY);
}
static void display(void)
{
const int window_width = glutGet(GLUT_WINDOW_WIDTH);
const int window_height = glutGet(GLUT_WINDOW_HEIGHT);
if( !window_width || !window_height )
return;
const float window_aspect = (float)window_width / (float)window_height;
glDisable(GL_SCISSOR_TEST);
glClearColor(0.4, 0.3, 0.5, 1.0);
glClearDepth(1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, window_width, window_height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-window_aspect, window_aspect, -1, 1, 2, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0., 0., -5.);
glPushMatrix();
glRotatef(scene.triangle_rotation, 0., 1., 0.);
draw_triangle();
glPopMatrix();
glutSwapBuffers();
}
static void special_key(int key, int x, int y)
{
switch(key) {
case GLUT_KEY_LEFT:
scene.triangle_rotation = fmod(scene.triangle_rotation + 5, 360);
break;
case GLUT_KEY_RIGHT:
scene.triangle_rotation = fmod(scene.triangle_rotation - 5, 360);
break;
default:
break;
}
glutPostRedisplay();
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutCreateWindow("Simple input altering scene demo");
glutDisplayFunc(display);
glutSpecialFunc(special_key);
glutMainLoop();
}
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