Dragging objects with mouse with glutWireCube() - c

Question

I'm working with OpenGL and I want to drag a cube with glutmotionfunc. I didn't finish at all, I don't know how to configure my views and I don't know what's wrong.
#include <GL/gl.h>
#include <GL/glut.h>
double rotate_y=0;
double rotate_x=0;
double rotate_z=0;
GLfloat X = 0.0f;
GLfloat Y = 0.0f;
GLfloat Z = 0.0f;
GLfloat scale = 1.0f;
float ancho=800;
float alto=600;
int perspectiva = 0;
float rx, ry;
void motion(int x, int y) // this is my motion function
// called when a mouse is in motion with a button down
{
printf("YYYMotion call back: %d, %d)\n", x, y);
rx = x;
ry = alto - y;
}
void display()
{
// Borrar pantalla y Z-buffer
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
// Resetear transformaciones
glLoadIdentity();
gluLookAt(1.0, 2.0, 50.0, //eye (x,y,z)
0.0, 0.0, 0.0, //at(x,y,z)
0.0, 1.0, 0.0); //up (x,y,z)
glScalef(scale, scale, scale);
glTranslatef((rx/ancho), (1-(ry/alto)), 0);
glFlush();
glutSwapBuffers();
}
void menu(int valor)
{
switch(valor)
{
case 1:
glutWireTorus(0.5,2.0,20,20);
break;
case 2:
glutWireTeapot(1.0);
break;
case 3:
glutWireSphere(0.8,50,50);
break;
case 4:
glutWireCube(1.0f);
break;
case 5:
glutWireIcosahedron();
break;
case 6:
glutWireOctahedron();
break;
case 7:
glutWireTetrahedron();
break;
case 8:
glutWireCone(0.5,1,5,5);
break;
case 9:
exit(1);
break;
}
}
void menu_opciones(void)
{
glutCreateMenu(menu);
glutAddMenuEntry("Torus",1);
glutAddMenuEntry("Tetera",2);
glutAddMenuEntry("Esfera",3);
glutAddMenuEntry("Cubo",4);
glutAddMenuEntry("Icosaedro",5);
glutAddMenuEntry("Octaedro",6);
glutAddMenuEntry("Tetraedro",7);
glutAddMenuEntry("Cono",8);
glutAddMenuEntry("Salir",9);
glutAttachMenu(GLUT_RIGHT_BUTTON);
}
void init()
{
glClearColor(0,0,0,0);
// Habilitar la prueba de profundidad de Z-buffer
glEnable(GL_DEPTH_TEST);
ancho = 800;
alto = 600;
}
void reshape(int w, int h)
{
glViewport(0, 0, w,h);
glMatrixMode(GL_PROJECTION);
menu_opciones();
glLoadIdentity();
//gluPerspective(80.0f, (GLfloat)w/(GLfloat)h, 0.2f, 30.0f);
//glOrtho(-2,2, -2, 2, 1, 10);
//glOrtho(-2, 2, -2, 2, -2, 2);
glFrustum (-1.0, 1.0, -1.0, 1.0, 2.5, 50.0);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char* argv[])
{
// Inicializar los parámetros GLUT y de usuario proceso
glutInit(&argc,argv);
// Solicitar ventana con color real y doble buffer con Z-buffer
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );
glutInitWindowSize (800, 600);
glutInitWindowSize(ancho, alto);
// Crear ventana
glutCreateWindow("");
init();
// Funciones de retrollamada
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMotionFunc( motion);
//glutKeyboardFunc(keyboard);
//glutSpecialFunc(specialKeys);
// Pasar el control de eventos a GLUT
glutMainLoop();
// Regresar al sistema operativo
return 0;
}

Answer 1

Where do you actually draw things? Something is missing:
void display()
{
// Borrar pantalla y Z-buffer
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
// Resetear transformaciones
glLoadIdentity();
gluLookAt(1.0, 2.0, 50.0, //eye (x,y,z)
0.0, 0.0, 0.0, //at(x,y,z)
0.0, 1.0, 0.0); //up (x,y,z)
glScalef(scale, scale, scale);
glTranslatef((rx/ancho), (1-(ry/alto)), 0);
/* where are things actually drawn? <<<<<<<<<<<<<<<<< */
glFlush();
glutSwapBuffers();
}
OpenGL is a drawing API, not a scene graph. When you call OpenGL drawing functions, all it does is drawing points, lines or triangles to a framebuffer. One at a time each on its own. There is no such thing as "adding a model to a scene" in OpenGL. Son in your drawing code you actually have to draw something, to see something. And if something changes in your scene you have to redraw (everything).