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/*
* Copyright © 2010 Ian D. Romanick
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#define _USE_MATH_DEFINES
#include <stdlib.h>
#include <math.h>
#include "revolve.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
void
revolve(const GLUvec4 *points, const GLUvec4 *normals, const float *u,
unsigned num_points,
const GLUvec4 *axis,
unsigned steps, float start_angle, float end_angle,
revolve_cb *cb, void *data, struct cb_buffer *buf)
{
const float angle_step = (end_angle - start_angle) / (float) (steps - 1);
const GLUvec4 tangent = {{ 0.0, 0.0, 1.0, 0.0 }};
unsigned i;
unsigned j;
for (i = 0; i < steps; i++) {
const float a = start_angle + (angle_step * i);
const float v = (float) i / (float) (steps - 1);
GLUmat4 r;
/* Generate a rotation matrix to rotate the position and the
* normal around the axis by the current angular step. This
* generates the new position and normal.
*/
gluRotate4v(& r, axis, a);
for (j = 0; j < num_points; j++) {
gluMult4m_4v(& buf->pos[buf->used], & r, & points[j]);
gluMult4m_4v(& buf->nrm[buf->used], & r, & normals[j]);
gluMult4m_4v(& buf->tng[buf->used], & r, & tangent);
buf->uv[buf->used].values[0] = u[j];
buf->uv[buf->used].values[1] = v;
buf->uv[buf->used].values[2] = 0.0;
buf->uv[buf->used].values[3] = 0.0;
buf->used++;
if (CB_BUFFER_IS_FULL(*buf)) {
(*cb)(data, buf->pos, buf->nrm, buf->tng,
buf->uv, buf->used);
CB_BUFFER_MAKE_EMPTY(*buf);
}
}
}
if (!CB_BUFFER_IS_EMPTY(*buf)) {
(*cb)(data, buf->pos, buf->nrm, buf->tng, buf->uv, buf->used);
CB_BUFFER_MAKE_EMPTY(*buf);
}
}
void
generate_sphere(double radius, unsigned slices, unsigned stacks,
_Bool normals_point_out,
revolve_cb *cb, void *data, struct cb_buffer *buf)
{
const GLUvec4 y_axis = {{ 0.0, 1.0, 0.0, 0.0 }};
GLUvec4 *positions;
GLUvec4 *normals;
float *u;
double latitude_step;
unsigned i;
positions = (GLUvec4 *) malloc((2 * sizeof(GLUvec4) + sizeof(float))
* (stacks + 1));
normals = positions + (stacks + 1);
u = (float *)(normals + (stacks + 1));
latitude_step = M_PI / (double)(stacks);
for (i = 0; i < (stacks + 1); i++) {
const double latitude = latitude_step * i;
normals[i].values[0] = sin(latitude);
normals[i].values[1] = cos(latitude);
normals[i].values[2] = 0.0;
normals[i].values[3] = 0.0;
gluMult4v_f(& positions[i],
& normals[i],
radius);
positions[i].values[3] = 1.0;
u[i] = (float) i / (float) stacks;
if (!normals_point_out) {
normals[i].values[0] = -normals[i].values[0];
normals[i].values[1] = -normals[i].values[1];
}
}
/* Note the rotation is *from* 2pi *to* 0. The counter-clockwise
* rotation ensures that the vertices are generated in the correct
* order to be drawn using triangle strips with back-face culling.
*/
revolve(positions, normals, u, stacks + 1, & y_axis,
slices + 1, 2.0 * M_PI, 0.0, cb, data, buf);
}
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