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/*
* MODULE NAME: round_cap.c
*
* FUNCTION:
* This module contains code that draws the round end-cap for round
* join-style tubing.
*
* HISTORY:
* written by Linas Vepstas August/September 1991
* split into multiple compile units, Linas, October 1991
* added normal vectors Linas, October 1991
*/
#include <malloc.h>
#include <stdlib.h>
#include <math.h>
#include <string.h> /* for the memcpy() subroutine */
#include <GL/tube.h>
#include "port.h"
#include "gutil.h"
#include "vvector.h"
#include "extrude.h"
#include "tube_gc.h"
#include "intersect.h"
#include "segment.h"
/* ============================================================ */
/* This routine does what it says: It draws the end-caps for the
* "round" join style.
*/
/* HACK ALERT HACK ALERT HACK ALERT HACK ALERT */
/* This #define should be replaced by some adaptive thingy.
* the adaptiveness needs to depend on relative angles and diameter of
* extrusion relative to screen size (in pixels).
*/
#define __ROUND_TESS_PIECES 5
void draw_round_style_cap_callback (int ncp,
double cap[][3],
float face_color[3],
gleDouble cut[3],
gleDouble bi[3],
double norms[][3],
int frontwards)
{
double axis[3];
double xycut[3];
double theta;
double *last_contour, *next_contour;
double *last_norm, *next_norm;
double *cap_z;
double *tmp;
char *malloced_area;
int i, j, k;
double m[4][4];
if (face_color != NULL) C3F (face_color);
/* ------------ start setting up rotation matrix ------------- */
/* if the cut vector is NULL (this should only occur in
* a degenerate case), then we can't draw anything. return. */
if (cut == NULL) return;
/* make sure that the cut vector points inwards */
if (cut[2] > 0.0) {
VEC_SCALE (cut, -1.0, cut);
}
/* make sure that the bi vector points outwards */
if (bi[2] < 0.0) {
VEC_SCALE (bi, -1.0, bi);
}
/* determine the axis we are to rotate about to get bi-contour.
* Note that the axis will always lie in the x-y plane */
VEC_CROSS_PRODUCT (axis, cut, bi);
/* reverse the cut vector for the back cap --
* need to do this to get angle right */
if (!frontwards) {
VEC_SCALE (cut, -1.0, cut);
}
/* get angle to rotate by -- arccos of dot product of cut with cut
* projected into the x-y plane */
xycut [0] = 0.0;
xycut [1] = 0.0;
xycut [2] = 1.0;
VEC_PERP (xycut, cut, xycut);
VEC_NORMALIZE (xycut);
VEC_DOT_PRODUCT (theta, xycut, cut);
theta = acos (theta);
/* we'll tesselate round joins into a number of teeny pieces */
theta /= (double) __ROUND_TESS_PIECES;
/* get the matrix */
urot_axis_d (m, theta, axis);
/* ------------ done setting up rotation matrix ------------- */
/* This malloc is a fancy version of:
* last_contour = (double *) malloc (3*ncp*sizeof(double);
* next_contour = (double *) malloc (3*ncp*sizeof(double);
*/
malloced_area = malloc ((4*3+1) *ncp*sizeof (double));
last_contour = (double *) malloced_area;
next_contour = last_contour + 3*ncp;
cap_z = next_contour + 3*ncp;
last_norm = cap_z + ncp;
next_norm = last_norm + 3*ncp;
/* make first copy of contour */
if (frontwards) {
for (j=0; j<ncp; j++) {
last_contour[3*j] = cap[j][0];
last_contour[3*j+1] = cap[j][1];
last_contour[3*j+2] = cap_z[j] = cap[j][2];
}
if (norms != NULL) {
for (j=0; j<ncp; j++) {
VEC_COPY ((&last_norm[3*j]), norms[j]);
}
}
} else {
/* in order for backfacing polygon removal to work correctly, have
* to have the sense in which the joins are drawn to be reversed
* for the back cap. This can be done by reversing the order of
* the contour points. Normals are a bit trickier, since the
* reversal is off-by-one for facet normals as compared to edge
* normals. */
for (j=0; j<ncp; j++) {
k = ncp - j - 1;
last_contour[3*k] = cap[j][0];
last_contour[3*k+1] = cap[j][1];
last_contour[3*k+2] = cap_z[k] = cap[j][2];
}
if (norms != NULL) {
if (__TUBE_DRAW_FACET_NORMALS) {
for (j=0; j<ncp-1; j++) {
k = ncp - j - 2;
VEC_COPY ((&last_norm[3*k]), norms[j]);
}
} else {
for (j=0; j<ncp; j++) {
k = ncp - j - 1;
VEC_COPY ((&last_norm[3*k]), norms[j]);
}
}
}
}
/* &&&&&&&&&&&&&& start drawing cap &&&&&&&&&&&&& */
for (i=0; i<__ROUND_TESS_PIECES; i++) {
for (j=0; j<ncp; j++) {
next_contour [3*j+2] -= cap_z[j];
last_contour [3*j+2] -= cap_z[j];
MAT_DOT_VEC_3X3 ( (&next_contour[3*j]), m, (&last_contour[3*j]));
next_contour [3*j+2] += cap_z[j];
last_contour [3*j+2] += cap_z[j];
}
if (norms != NULL) {
for (j=0; j<ncp; j++) {
MAT_DOT_VEC_3X3 ( (&next_norm[3*j]), m, (&last_norm[3*j]));
}
}
/* OK, now render it all */
if (norms == NULL) {
draw_segment_plain (ncp, (gleVector *) next_contour,
(gleVector *) last_contour, 0, 0.0);
} else
if (__TUBE_DRAW_FACET_NORMALS) {
draw_binorm_segment_facet_n (ncp,
(gleVector *) next_contour,
(gleVector *) last_contour,
(gleVector *) next_norm,
(gleVector *) last_norm, 0, 0.0);
} else {
draw_binorm_segment_edge_n (ncp,
(gleVector *) next_contour,
(gleVector *) last_contour,
(gleVector *) next_norm,
(gleVector *) last_norm, 0, 0.0);
}
/* swap contours */
tmp = next_contour;
next_contour = last_contour;
last_contour = tmp;
tmp = next_norm;
next_norm = last_norm;
last_norm = tmp;
}
/* &&&&&&&&&&&&&& end drawing cap &&&&&&&&&&&&& */
/* Thou shalt not leak memory */
free (malloced_area);
}
/* ==================== END OF FILE =========================== */
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