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/*
* File: prism.c
*
* Create a prism from a polygonal cross-section in XY.
* The points must be given in counter-clockwise order as viewed from
* the front (+ve Z).
*
* Author: David Jones
* djones@awesome.berkeley.edu
* 11may91 djones
*
* Adapted for inclusion into the SIPP package: Inge Wallin
* Extended with 2D texture support: Jonas Yngvesson
*/
#include <stdio.h>
#include <math.h>
#include <sipp.h>
#include <primitives.h>
#include <xalloca.h>
Object *
sipp_prism(num_points, points, length, surface, shader, texture)
int num_points;
Vector * points;
double length;
void * surface;
Shader * shader;
int texture;
{
Object * prism;
double * u;
double * v;
int i;
int j;
switch (texture) {
case NATURAL:
u = (double *)alloca((num_points + 1) * sizeof(double));
u[0] = 0.0;
for (i = 1; i <= num_points; i++) {
u[i] = u[i - 1] + sqrt(((points[i % num_points].x
- points[i - 1].x)
* (points[i % num_points].x
- points[i - 1].x))
+ ((points[i % num_points].y
- points[i - 1].y)
* (points[i % num_points].y
- points[i - 1].y)));
}
for (i = 0; i <= num_points; i++) {
u[i] /= u[num_points];
}
break;
case SPHERICAL:
v = (double *)alloca((num_points + 1) * sizeof(double));
for (i = 0; i < num_points; i++) {
v[i] = (atan(length / 2.0
/ sqrt(points[i].x * points[i].x
+ points[i].y * points[i].y))
/ M_PI + 0.5);
}
v[i] = v[0];
case CYLINDRICAL: /* Fall trough */
u = (double *)alloca((num_points + 1) * sizeof(double));
u[0] = atan2(points[0].y, points[0].x);
for (i = 1; i < num_points; i++) {
u[i] = atan2(points[i].y, points[i].x) - u[0];
if (u[i] < 0.0) {
u[i] += 2.0 * M_PI;
}
u[i] /= (2.0 * M_PI);
}
u[0] = 0.0;
u[i] = 1.0;
break;
case WORLD:
default:
break;
}
prism = object_create();
/* The top. */
for (i = 0; i < num_points ; ++i) {
switch (texture) {
case NATURAL:
case CYLINDRICAL:
case SPHERICAL:
vertex_tx_push(points[i].x, points[i].y, length / 2.0,
0.0, 1.0, 0.0);
break;
case WORLD:
default:
vertex_tx_push(points[i].x, points[i].y, length / 2.0,
points[i].x, points[i].y, length / 2.0);
break;
}
}
polygon_push();
object_add_surface(prism, surface_create(surface, shader) );
/* The bottom */
for (i = num_points - 1; i >= 0 ; --i) {
switch (texture) {
case NATURAL:
case CYLINDRICAL:
case SPHERICAL:
vertex_tx_push(points[i].x, points[i].y, -length / 2.0,
0.0, 0.0, 0.0);
break;
case WORLD:
default:
vertex_tx_push(points[i].x, points[i].y, -length / 2.0,
points[i].x, points[i].y, -length / 2.0);
break;
}
}
polygon_push();
object_add_surface(prism, surface_create(surface, shader) );
/* The sides */
for (i = 0; i < num_points ; ++i) {
j = i + 1;
if (j == num_points)
j=0;
switch (texture) {
case NATURAL:
case CYLINDRICAL:
vertex_tx_push(points[i].x, points[i].y, length / 2.0,
u[i], 1.0, 0.0);
vertex_tx_push(points[i].x, points[i].y, -length / 2.0,
u[i], 0.0, 0.0);
vertex_tx_push(points[j].x, points[j].y, -length / 2.0,
u[i + 1], 0.0, 0.0);
vertex_tx_push(points[j].x, points[j].y, length / 2.0,
u[i + 1], 1.0, 0.0);
break;
case SPHERICAL:
vertex_tx_push(points[i].x, points[i].y, length / 2.0,
u[i], v[i], 0.0);
vertex_tx_push(points[i].x, points[i].y, -length / 2.0,
u[i], 1.0 - v[i], 0.0);
vertex_tx_push(points[j].x, points[j].y, -length / 2.0,
u[i + 1], 1.0 - v[i + 1], 0.0);
vertex_tx_push(points[j].x, points[j].y, length / 2.0,
u[i + 1], v[i + 1], 0.0);
break;
case WORLD:
default:
vertex_tx_push(points[i].x, points[i].y, length / 2.0,
points[i].x, points[i].y, length / 2.0);
vertex_tx_push(points[i].x, points[i].y, -length / 2.0,
points[i].x, points[i].y, -length / 2.0);
vertex_tx_push(points[j].x, points[j].y, -length / 2.0,
points[j].x, points[j].y, -length / 2.0);
vertex_tx_push(points[j].x, points[j].y, length / 2.0,
points[j].x, points[j].y, length / 2.0);
break;
}
polygon_push();
object_add_surface(prism, surface_create(surface, shader) );
}
return prism;
}
/*
* A square block. Generated as a prism.
*/
Object *
sipp_block(xsize, ysize, zsize, surface, shader, texture)
double xsize;
double ysize;
double zsize;
void * surface;
Shader * shader;
int texture;
{
Vector coor[4];
xsize /= 2.0;
ysize /= 2.0;
coor[0].x = xsize; coor[0].y = -ysize;
coor[1].x = xsize; coor[1].y = ysize;
coor[2].x = -xsize; coor[2].y = ysize;
coor[3].x = -xsize; coor[3].y = -ysize;
return sipp_prism(4, coor, zsize, surface, shader, texture);
}
/*
* A cube.
*/
Object *
sipp_cube(size, surface, shader, texture)
double size;
void * surface;
Shader * shader;
int texture;
{
return sipp_block(size, size, size, surface, shader, texture);
}
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