/* * cylinder2.c: * * This program displays two intersecting cylinders, using a * different surface material for each cylinder. In addition, each * cylinder is lit by two light source. * * This program requires the z-buffer option. * */
#include <gl.h> #include <math.h> #include <stdio.h>
#define RADIUS 0.9 #define TWOPI 6.28318530 #define PI 3.14159265
/* define black RGB color */
float blackvec[3] = {0.0, 0.0, 0.0};
Matrix idmat = {1.0,0.0,0.0,0.0, /* identity matrix */
0.0,1.0,0.0,0.0,
0.0,0.0,1.0,0.0,
0.0,0.0,0.0,1.0};
/* define a polygon with some structures */
typedef struct { /* 3-D vertex structure */
Coord x;
Coord y;
Coord z;
} POINT;
typedef struct { /* lighted polygon struct */
POINT vertex[4];
POINT normal[4];
} POLYGON;
int number_of_polys; /* cylinder polygon count */ POLYGON *polygon; /* polygon list pointer */
/* define property arrays */
float shiny_material[] =
{SPECULAR, 0.8, 0.8, 0.8, /* light gray reflectance */
DIFFUSE, 0.4, 0.4, 0.4, /* gray reflectance */
SHININESS, 30.0, /* focused highlight */
LMNULL};
float purple_material[] =
{SPECULAR, 0.3, 0.3, 0.3, /* gray reflectance */
DIFFUSE, 0.8, 0.0, 0.8, /* purple reflectance */
SHININESS, 3.0, /* unfocused highlight */
AMBIENT, 0.2,0.0,0.2, /* purple reflectance */
LMNULL};
float blue_light[] =
{LCOLOR, 0.0,0.0,0.6, /* blue light */
POSITION, 0.0,0.1,0.0,0.0, /* Y axis at infinity */
LMNULL};
/*
** def_light_calc()
** Tell the Graphics Library to DEFINE a
** lighting calculation that accounts for
** ambient, diffuse, and specular reflection.
** This lighting calculation defines a second
** material and light source.
*/
def_light_calc() {
lmdef(DEFMATERIAL, 1, 11, shiny_material);
lmdef(DEFMATERIAL, 2, 15, purple_material);
lmdef(DEFLIGHT, 1, 0, NULL);
lmdef(DEFLIGHT, 2, 10, blue_light);
lmdef(DEFLMODEL, 1, 0, NULL);
}
/*
** use_light_calc()
** Tell the Graphics Library to USE
** the lighting calculation that we
** defined earlier.
*/
use_light_calc()
{
lmbind(LIGHT0, 1); /* use light source description 1 */
lmbind(LIGHT1, 2); /* use light source description 2 */
lmbind(LMODEL, 1); /* use lighting model 1 */
}
/*
** make_cylinder()
** Draw a cylinder using (2 * n) polygons
** to approximate the curvature and n polygons
** to describe the length. This requires (2 * n^2)
** polygons to describe the cylinder. Compute
** the surface normal at each vertex so we can
** use the hardware lighting facility to perform
** lighting calculations.
*/
make_cylinder(n)
int n;
{
POLYGON *p; /* polygon list pointer */
float theta, dtheta,/* current angle and angle */
/* increment around section */
x, dx; /* current position and */
/* increment along cylinder side */
int vertex_i; /* vertex counter */
/* allocate and point to enough */
/* memory for all the polygons */
number_of_polys = 2 * n * n;
p = polygon = (POLYGON *)
malloc(number_of_polys * sizeof(POLYGON));
dx = 3.0/n; /* n polygons for 3.0 units of length */
dtheta = PI/n; /* length of polygon along curvature */
/* for each layer of polygons */
/* along length of cylinder ... */
for (x = -1.5; x < 1.5; x = x+dx) {
/* ... and for each polygon */
/* describing the circumference */
for (theta = 0.0; theta < TWOPI; theta += dtheta) {
/* calculate the four points */
/* describing the polygon */
p->vertex[0].x = p->vertex[1].x = x;
p->vertex[0].y = p->vertex[3].y =
RADIUS * cos(theta);
p->vertex[0].z = p->vertex[3].z =
RADIUS * sin(theta);
p->vertex[1].y = p->vertex[2].y =
RADIUS * cos(theta + dtheta);
p->vertex[1].z = p->vertex[2].z =
RADIUS * sin(theta + dtheta);
p->vertex[2].x = p->vertex[3].x = x + dx;
/* calculate the four normals of unit length */
for (vertex_i = 0; vertex_i < 4; vertex_i++) {
p->normal[vertex_i].x = 0;
p->normal[vertex_i].y =
p->vertex[vertex_i].y / RADIUS;
p->normal[vertex_i].z =
p->vertex[vertex_i].z / RADIUS;
}
p++;
}
}
}
/*
** draw_cylinder()
** This subroutine increments through the 4
** vertices describing each polygon of the
** cylinder defined in make_cylinder. Note
** how a normal is sent to the graphics
** hardware before each vertex so that the
** lighting facility will compute the color
** for each vertex based on the lighting
** parameters that we are using.
*/
draw_cylinder()
{
POLYGON *p; /* pointer into polygon list */
int poly_i; /* polygon counter */
/* start at first polygon and */
/* increment through all of them */
p = polygon;
for (poly_i = 0; poly_i < number_of_polys; poly_i++) {
bgnpolygon(); /* describe the polygon */
n3f(&p->normal[0]);
v3f(&p->vertex[0]);
n3f(&p->normal[1]);
v3f(&p->vertex[1]);
n3f(&p->normal[2]);
v3f(&p->vertex[2]);
n3f(&p->normal[3]);
v3f(&p->vertex[3]);
endpolygon();
p++; /* go to the next polygon */
}
}
/*
** Main Program
*/
main()
{
int i;
/* set up graphics environment */
prefposition(100, 600, 100, 600);
winopen("cylinder");
RGBmode();
doublebuffer();
gconfig();
lsetdepth(0, 0x7FFFFF);
zbuffer(TRUE);
/* Use mmode() to set up projection */
/* and viewing matrices for lighting */
mmode(MVIEWING);
perspective(400, 1.0, 4.0, 12.0);
loadmatrix(idmat);
lookat(0.0,0.0,8.0,0.0,0.0,0.0,0);
/* let there be light !!!! */
def_light_calc();
use_light_calc();
/* Rotate cylinders in 2 deg. increments */
/* about Y and Z axis for 180 frames */
make_cylinder(25);
for (i = 0; i < 180; i++) {
c3f(blackvec);
clear();
zclear();
pushmatrix();
rot(i * 2.0, 'Z');
rot(i * 2.0, 'Y');
/* use white shiny material for cyl 1*/
lmbind(MATERIAL, 1);
draw_cylinder();
pushmatrix();
rot(90.0, 'Y');
scale(0.9,0.9,0.9);
/* use purple rough material for cyl 2 */
lmbind(MATERIAL, 2);
draw_cylinder();
popmatrix();
popmatrix();
swapbuffers();
}
sleep(3);
}
The bgnpolygon or endpolygon subroutine, lmbind subroutine, lmdef subroutine, n3f subroutine, scale subroutine, v subroutine.
Lighting Basics in GL3.2 Version 4 for AIX: Programming Concepts.