#include <stdio.h>
#include "vogle.h"

static char ident[] = "@(#) various combinations of viewing and projection transformations";

void drawtetra(){ /* generate a tetrahedron as a series of move draws */
        
        move(-0.5,  0.866, -0.5);
        draw(-0.5, -0.866, -0.5);
        draw( 1.0,  0.0,   -0.5);
        draw(-0.5,  0.866, -0.5);
        draw( 0.0,  0.0,    1.5);
        draw(-0.5, -0.866, -0.5);
        move( 1.0,  0.0,   -0.5);
        draw( 0.0,  0.0,    1.5);
        
        /* 
         * Label the vertices.
         */
        color(WHITE);
        textsize(0.3, 0.5);             /* set the text size */
        move(-0.5,  0.866, -0.5);
        drawchar('a');
        move(-0.5, -0.866, -0.5);
        drawchar('b');
        move( 1.0,  0.0,   -0.5);
        drawchar('c');
        move( 0.0,  0.0,    1.5);
        drawchar('d');
}

/*
 * various combinations of viewing and projection transformations
 */
int main( int argc, char *argv[] ){
        char device[20];

        fprintf(stderr,"Enter device name: ");
        gets(device);
        vinit(device);

        color(BLACK);
        clear();

        /*
         * we want to draw just within the boundaries of the screen
         */
        viewport(-0.9, 0.9, -0.9, 0.9);


        ortho2(-5.0, 5.0, -5.0, 5.0);   /* set the world size */

        color(RED);
        rect(-5.0, -5.0, 5.0, 5.0);     /* draw a boundary frame */

        /*
         * set up a perspective projection with a field of view of
         * 40.0 degrees, aspect ratio of 1.0, near clipping plane 0.1,
         * and the far clipping plane at 1000.0.
         */
        perspective(40.0, 1.0, 0.1, 1000.0);

        /*
         * we want the drawing to be done with our eye point at (5.0, 8.0, 5.0)
         * looking towards (0.0, 0.0, 0.0). The last parameter gives a twist
         * in degrees around the line of sight, in this case zero.
         */
        lookat(5.0, 8.0, 5.0, 0.0, 0.0, 0.0, 0.0);

        drawtetra();

        move2(-4.5, -4.5);
        textsize(0.6, 0.9);             /* set the text size */
        drawstr("perspective/lookat");

        getkey();

        /*
         * window can also be used to give a perspective projection. Its
         * arguments are 6 clipping planes, left, right, bottom, top, near,
         * and far.
         */
        window(-5.0, 5.0, -5.0, 5.0, -5.0, 5.0);
        /*
         * as window replaces the current transformation matrix we must
         * specify our viewpoint again.
         */
        lookat(5.0, 8.0, 5.0, 0.0, 0.0, 0.0, 0.0);

        color(BLACK);
        clear();

        color(GREEN);
        rect(-5.0, -5.0, 5.0, 5.0);

        drawtetra();

        move2(-4.5,-4.5);
        textsize(0.6, 0.9);             /* set the text size */
        drawstr("window/lookat");

        getkey();

        /*
         * set up our original perspective projection again.
         */
        perspective(40.0, 1.0, 0.1, 1000.0);
        /*
         * polarview also specifies our viewpoint, but, unlike lookat, in polar
         * coordinates. Its arguments are the distance from the world origin, an
         * azimuthal angle in the x-y plane measured from the y axis, an 
         * incidence angle in the y-z plane measured from the z axis, and a
         * twist around the line of sight.
         */
        polarview(15.0, 30.0, 30.0, 30.0);

        color(BLACK);
        clear();

        color(MAGENTA);
        rect(-5.0, -5.0, 5.0, 5.0);

        drawtetra();

        move2(-4.5,-4.5);
        textsize(0.6, 0.9);             /* set the text size */
        drawstr("perspective/polarview");

        getkey();

        /*
         * once more with window for comparison
         */
        window(-4.0, 4.0, -4.0, 4.0, -4.0, 4.0);
        polarview(6.0, 20.0, -30.0, 70.0);

        color(BLACK);
        clear();

        color(YELLOW);
        rect(-5.0, -5.0, 5.0, 5.0);

        drawtetra();

        move2(-4.5,-4.5);
        textsize(0.6, 0.9);             /* set the text size */
        drawstr("window/polarview");

        getkey();

        vexit();
}