/* Simple demo of a 2D surface in a 3D world, where the surface is defined
   by Bezier curves.  This gives a wire-frame look at a flag on a
   flagpole.

   Scott D. Anderson
   Fall 2000 original version
   Fall 2003 adapted to use TW
*/

#include <tw.h>

GLfloat flag[16][3] = {
    {0.0, 0.0, 0.0},                /* ll corner */
    {0.1, 0.2, 0.0},                /* ll edge */
    {0.1, 0.8, 0.0},                /* ul edge */
    {0.0, 1.0, 0.0},                /* ul corner */

    {0.2, 0.1, 0.2},                /* ll edge, curving forward */
    {0.2, 0.2, 0.2},                /* ll interior corner */
    {0.2, 0.8, 0.1},                /* ul interior corner */
    {0.2, 0.9, 0.1},                /* top left edge */

    {0.8, 0.2, -0.2},                /* lr edge, curving forward from behind */
    {0.8, 0.2, -0.1},                /* lr interior corner */
    {0.7, 0.8, -0.1},                /* ur interior corner */
    {0.7, 0.9,  0.0},                /* ur edge */

    {0.9, 0.3, 0.0},                /* lr corner */
    {0.8, 0.4, -0.1},                /* lr edge */
    {0.8, 0.8, 0.0},                /* ur edge */
    {0.9, 0.9, -0.1}                /* ur corner */
};

bool wire=true;                        /* whether to use wire or fill */

// This draws the whole surface, using a mesh with `nsteps' in each direction
void draw_bezier_surface(int nsteps, GLfloat* control_points) {
    glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 4, control_points);
    glEnable(GL_MAP2_VERTEX_3);
    // set up grid and generate the desired surface
    glMapGrid2f(nsteps, 0.0, 1.0, nsteps, 0.0, 1.0);
    if(wire) 
        glEvalMesh2(GL_LINE, 0, nsteps, 0, nsteps);
    else
        glEvalMesh2(GL_FILL, 0, nsteps, 0, nsteps);
}

// Draws a flagpole of height 10 at the origin, using the current color

void draw_flag() {
    int nsteps=8;
    // draw flagpole
    glLineWidth(5);                /* pole is this many pixels wide */
    glBegin(GL_LINES);
    {
        glVertex3f(0,0,0);
        glVertex3f(0,10,0);
    }
    glEnd();

    // draw flag
    glLineWidth(1);                /* flag lines are 1 pixel wide */
    glPushMatrix();
    glTranslatef(0,5,0);
    glScalef(5,5,5);
    draw_bezier_surface(8,flag[0]);
    glPopMatrix();

    // knob at the top. The radius of this is a guess.  Should correspond
    // to 5 pixels.
    
    glPushMatrix();
    glTranslatef(0,10,0);
    glutSolidSphere(0.4,10,10);
    glPopMatrix();
}

void toggleWire(unsigned char k, int x, int y) {
    wire = !wire;
    glutPostRedisplay();
}

void display() {
    twDisplayInit();
    twCamera();
    glPushAttrib(GL_ALL_ATTRIB_BITS);

    glColor3f(1,1,1);                /* draw in white */

    draw_flag();

    glPopAttrib();
    glFlush();
    glutSwapBuffers();
}


int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(500, 500);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    twBoundingBox(0,5,0,10,-1,1);
    twMainInit();
    twKeyCallback('w',toggleWire,"toggle wireframe flag");
    glutMainLoop();                   
}