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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.
*/
#include "glu3.h"
#include "revolve.h"
#include "mesh.h"
/**
* \name Call-back functions for sphere generation routine
*/
/*@{*/
static void sphere_revolve_cb(void *data,
const GLUvec4 *position,
const GLUvec4 *normal,
const GLUvec4 *tangent,
const GLUvec4 *uv);
static void sphere_begin_cb(void *data, GLenum mode);
static void sphere_index_cb(void *data, unsigned index);
static void sphere_end_cb(void *data);
/*@}*/
/**
* GLUsphere decorator to implement call-backs
*
* To generate the sphere data, the \c GLUsphere class interfaces with various
* C functions that use a call-back mechanism. These call-backs are analogous
* the \c emit_vertex, \c emit_begin, \c emit_index, and \c emit_end methods
* that \c GLUsphere subclasses will provide.
*
* However, these methods are all \c protected. As a result the non-class
* call-back functions cannot call these methods unless they are \c friend
* functions. It is undesireable to expose the implementation detail in the
* application-facing header file. This can be worked around by creating a
* dummy subclass of \c GLUsphere that only contains the \c friend function
* declarations. Pointers to \c GLUsphere objects can be cast to pointers to
* \c GLUsphereFriend objects without side-effect.
*
* This is arguably a mis-use of the "decorator" pattern, but it is the most
* efficient way to do this.
*/
class GLUsphereFriend : public GLUsphere {
friend void sphere_revolve_cb(void *data,
const GLUvec4 *position,
const GLUvec4 *normal,
const GLUvec4 *tangent,
const GLUvec4 *uv);
friend void sphere_begin_cb(void *data, GLenum mode);
friend void sphere_index_cb(void *data, unsigned index);
friend void sphere_end_cb(void *data);
};
GLUsphere::GLUsphere(GLdouble radius, GLint slices, GLint stacks)
{
this->radius = radius;
this->slices = (slices < 4) ? 4 : (unsigned) slices;
this->stacks = (stacks < 4) ? 4 : (unsigned) stacks;
}
unsigned
GLUsphere::vertex_count(void) const
{
/* Each line of vertices from the north pole to the south pole consists
* of (stacks+1) vertices. There are a total of (slices+1) of these
* lines of vertices.
*/
return (slices + 1) * (stacks + 1);
}
unsigned
GLUsphere::primitive_count(void) const
{
/* For each slice there is a triangle strip from the north pole to the
* south pole.
*/
return slices;
}
unsigned
GLUsphere::element_count(void) const
{
/* Each slice is a triangle strip represented by 2 elements plus
* 2 elements for each stack;
*/
return slices * (2 * (stacks + 1));
}
static void
sphere_revolve_cb(void *data, const GLUvec4 *position, const GLUvec4 *normal,
const GLUvec4 *tangent, const GLUvec4 *uv)
{
GLUsphereFriend *s = (GLUsphereFriend *) data;
s->emit_vertex(*position, *normal, *tangent, *uv);
}
static void
sphere_begin_cb(void *data, GLenum mode)
{
GLUsphereFriend *s = (GLUsphereFriend *) data;
s->emit_begin(mode);
}
static void
sphere_index_cb(void *data, unsigned index)
{
GLUsphereFriend *s = (GLUsphereFriend *) data;
s->emit_index(index);
}
static void
sphere_end_cb(void *data)
{
GLUsphereFriend *s = (GLUsphereFriend *) data;
s->emit_end();
}
void
GLUsphere::generate(void)
{
generate_sphere(radius, slices, stacks,
normals_point_out,
sphere_revolve_cb, (void *) this);
generate_triangle_mesh(slices, stacks + 1, stacks + 1,
sphere_begin_cb,
sphere_index_cb,
sphere_end_cb,
(void *) this);
}
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