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函数说明：
如有查询两个面之间的边缘的凸度。该凸值UF_FACET_IS_CONVEX，UF_IS_FACET_CONCAVE，和UF_FACET_CONVEXITY_NOT_DETERMINED;最后的这些表明，相邻的边缘的两个小面是非常近共面和边缘因此是否应该考虑凸或凹还不清楚。 （请注意，一个ifail是如果指定的返回边是开放的。）

函数参数：
第1个参数为输入：
model代表参数变量，tag_t 为输入参数类型，该模型

第2个参数为输入：
输入int 整数型的参数，参数的变量格式为facet_id，小面的ID。

第3个参数为输入：
输入int 整数型的参数，参数的变量格式为edge_in_facet，为此凸被询问的边缘。

第4个参数为输出：
输出int * 整数型的参数，参数的变量格式为convexity，边缘的凸度。

UF_FACET_ask_edge_convexity函数实例代码演示：
这个示例程序创建一个四面体的面模型。 它然后检查模型中的边缘的邻接和凸。最后，它会从四面体一个方面，并增加了另一三个方面的顶点，其中在四面体的内部向上推使得有在所得模型三凹边。 它即可查询并打印所有模型边缘的凸度。
[quote]
#include <stdio.h>
#include <uf.h>
#include <uf_modl.h>
#include <uf_assem.h>
#include <uf_facet.h>
/*--------------------------------------------------------------*/
/*ARGSUSED*/
extern void ufusr( char *param, int *retcod, int param_len )
{
UF_initialize();
*retcod = example2();
UF_terminate();
}
/*--------------------------------------------------------------*/
static int example2( void )
{
int ifail;
tag_t part_tag;
int i;
tag_t new_model;
double facet_vertices[30][3];
double facet_normals[30][3];
int adjacencies[30];
int facets[7];
int edge;
int adjacent_facets[3];
int facet_id;
int edge_in_adjacent_facet;
int num_facets_in_model;
logical model_convexity;
/*
First create a part in which we will initially create a
block.
*/
ifail = UF_PART_new( "uf_facet_exp2_test_part",
1 /* MM */,
&part_tag ); /* 1 = mm */
if ( ifail != 0 )
{
printf( "**ERR: Failed to create new part ifail %d\n",
ifail );
return 1;
}
ifail = UF_ASSEM_set_work_part( part_tag );
UF_FACET_create_model( part_tag, &new_model );
facet_vertices[0][0] = 0.0;
facet_vertices[0][1] = 0.0;
facet_vertices[0][2] = 0.0;

facet_vertices[1][0] = 0.03;
facet_vertices[1][1] = 0.05;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.060;
facet_vertices[2][1] = 0.0;
facet_vertices[2][2] = 0.0;
adjacencies[0] = UF_FACET_NULL_FACET_ID;
adjacencies[1] = UF_FACET_NULL_FACET_ID;
adjacencies[2] = UF_FACET_NULL_FACET_ID;
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+0 );
facet_vertices[0][0] = 0.0;
facet_vertices[0][1] = 0.0;
facet_vertices[0][2] = 0.0;

facet_vertices[1][0] = 0.060;
facet_vertices[1][1] = 0.0;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.03;
facet_vertices[2][1] = 0.03;
facet_vertices[2][2] = 0.05;
adjacencies[0] = facets[0];
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+1 );
facet_vertices[0][0] = 0.060;
facet_vertices[0][1] = 0.0;
facet_vertices[0][2] = 0.0;
facet_vertices[1][0] = 0.03;
facet_vertices[1][1] = 0.05;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.03;
facet_vertices[2][1] = 0.03;
facet_vertices[2][2] = 0.05;
adjacencies[0] = facets[0];
adjacencies[1] = UF_FACET_NULL_FACET_ID;
adjacencies[2] = facets[1];
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+2 );
facet_vertices[0][0] = 0.03;
facet_vertices[0][1] = 0.05;
facet_vertices[0][2] = 0.0;
facet_vertices[1][0] = 0.0;
facet_vertices[1][1] = 0.0;
facet_vertices[1][2] = 0.0;

facet_vertices[2][0] = 0.03;
facet_vertices[2][1] = 0.03;
facet_vertices[2][2] = 0.05;
adjacencies[0] = facets[0];
adjacencies[1] = facets[1];
adjacencies[2] = facets[2];
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+3 );
facet_id = UF_FACET_NULL_FACET_ID;
UF_FACET_cycle_facets( new_model, &facet_id );
while ( facet_id != UF_FACET_NULL_FACET_ID )
{
for ( edge = 0; edge < 3; edge++ )
{
UF_FACET_ask_adjacent_facet( new_model,
facet_id,
edge,
&adjacent_facets[edge],
&edge_in_adjacent_facet );
}
printf( "facet index: %d\n", facet_id );

printf( "\tadjacent_facets: [%d,%d,%d]\n",
adjacent_facets[0],
adjacent_facets[1],
adjacent_facets[2] );
UF_FACET_cycle_facets( new_model, &facet_id );
}
UF_FACET_is_model_convex( new_model, &model_convexity );
printf( "Model %s convex\n",
(model_convexity) ? "IS" : "IS NOT" );
/*
Now create a facet topology containing some concave
edges, to get this delete the first facet in the tetrahedron
and replace it with three facets the shared vertex of which
is towards the top vertex of the tetrahedron.
*/
UF_FACET_del_facet_from_model( new_model, facets[0] );
facet_vertices[0][0] = 0.060;
facet_vertices[0][1] = 0.0;
facet_vertices[0][2] = 0.0;
facet_vertices[1][0] = 0.0;
facet_vertices[1][1] = 0.0;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.02;
facet_vertices[2][1] = 0.02;
facet_vertices[2][2] = 0.01;
adjacencies[0] = facets[1];
adjacencies[1] = UF_FACET_NULL_FACET_ID;
adjacencies[2] = UF_FACET_NULL_FACET_ID;
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+5 );
facet_vertices[0][0] = 0.03;
facet_vertices[0][1] = 0.05;
facet_vertices[0][2] = 0.0;
facet_vertices[1][0] = 0.060;
facet_vertices[1][1] = 0.0;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.02;
facet_vertices[2][1] = 0.02;
facet_vertices[2][2] = 0.01;
adjacencies[0] = facets[2];
adjacencies[1] = facets[5];
adjacencies[2] = UF_FACET_NULL_FACET_ID;
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+6 );
facet_vertices[0][0] = 0.0;
facet_vertices[0][1] = 0.0;
facet_vertices[0][2] = 0.0;

facet_vertices[1][0] = 0.03;
facet_vertices[1][1] = 0.05;
facet_vertices[1][2] = 0.0;
facet_vertices[2][0] = 0.02;
facet_vertices[2][1] = 0.02;
facet_vertices[2][2] = 0.01;
adjacencies[0] = facets[3];
adjacencies[1] = facets[6];
adjacencies[2] = facets[5];
UF_FACET_add_facet_to_model( new_model,
3,
facet_vertices,
NULL,
adjacencies,
facets+7 );
UF_FACET_model_edits_done( new_model );
/*
Now look at the edge convexity again.
*/
printf( "Edge convexity for %u\n", new_model );
facet_id = UF_FACET_NULL_FACET_ID;
UF_FACET_cycle_facets( new_model, &facet_id );
while ( facet_id != UF_FACET_NULL_FACET_ID )
{
int verts_in_facet;
UF_FACET_ask_num_verts_in_facet( new_model,
facet_id,
&verts_in_facet );
/*
For each vertex print the vertex coordinates and the
vertex normal.
*/
UF_FACET_ask_vertices_of_facet( new_model,
facet_id,
&verts_in_facet,
facet_vertices );
UF_FACET_ask_normals_of_facet( new_model,
facet_id,
&verts_in_facet,
facet_normals );
for ( i=0 ; i < verts_in_facet ; i++ )
{
printf( " Vertex %d: (%g, %g, %g)\n",
i, facet_vertices[i][0],
facet_vertices[i][1],
facet_vertices[i][2] );
printf( " Normal %d (%g, %g, %g)\n",
i, facet_normals[i][0],
facet_normals[i][1],
facet_normals[i][2] );
}
for ( i=0 ; i < verts_in_facet ; i++ )
{
int convexity;
UF_FACET_ask_edge_convexity( new_model,
facet_id,
i,
&convexity );
printf( " Facet %d: Edge %d: %s\n", facet_id, i,
(convexity == UF_FACET_IS_CONVEX) ?
"IS CONVEX" :
(convexity == UF_FACET_IS_CONCAVE) ?
"IS CONCAVE" :
"CONVEXITY IS NOT DETERMINED"
);
/*
Now check that the convexity of the corresponding
edge in the adjacent facet is consistent.
*/
{
int adjacent_facet_id;
int adj_convexity;
UF_FACET_ask_adjacent_facet( new_model,
facet_id,
i,
&adjacent_facet_id,
&edge_in_adjacent_facet
);

UF_FACET_ask_edge_convexity( new_model,
adjacent_facet_id,
edge_in_adjacent_facet,
&adj_convexity );
if ( convexity != adj_convexity )
{
printf( " **ERR: Edge convexity wrong\n" );
}
}
}
UF_FACET_cycle_facets( new_model, &facet_id );
}
UF_FACET_ask_n_facets_in_model(new_model, &num_facets_in_model);
printf( "There are %d facets in the final model\n",
num_facets_in_model );
UF_FACET_is_model_convex( new_model, &model_convexity );
printf( "Model %s convex\n",
(model_convexity) ? "IS" : "IS NOT" );
return 0;
}

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