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/*
* MODULE NAME: ex_angle.c
*
* FUNCTION:
* This module contains code that draws extrusions with angled
* joins ("angle join style"). It also inserts colors and normals
* where necessary, if appropriate.
*
* HISTORY:
* written by Linas Vepstas August/September 1991
* split into multiple compile units, Linas, October 1991
* added normal vectors Linas, October 1991
* "code complete" (that is, I'm done), Linas Vepstas, October 1991
* work around OpenGL's lack of support for concave polys, June 1994
*/
#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 "tube_gc.h"
#include "extrude.h"
#include "intersect.h"
#include "segment.h"
/* ============================================================ */
/*
* Algorithmic trivia:
*
* There is a slight bit of trivia which the super-duper exacto coder
* needs to know about the code in this module. It is this:
*
* This module attempts to correctly treat contour normal vectors
* by applying the inverse transpose of the 2D contour affine
* transformation to the 2D contour normals. This is perfectly correct,
* when applied to the "raw" join style. However, if the affine transform
* has a strong rotational component, AND the join style is angle or
* cut, then the normal vectors would continue to rotate as the
* intersect point is extrapolated.
*
* The extrapolation of the inverse-transpose matrix to the intersection
* point is not done. This would appear to be overkill for most
* situations. The viewer might possibly detect an artifact of the
* failure to do this correction IF all three of the following criteria
* were met:
* 1) The affine xform has a strong rotational component,
* 2) The angle between two succesive segments is sharp (greater than 15 or
* 30 degrees).
* 3) The join style is angle or cut.
*
* However, I beleive that it is highly unlikely that the viewer will
* detect any artifacts. The reason I beleive this is that a strong
* rotational component will twist a segment so strongly that the more
* visible artifact will be that a segment is composed of triangle strips.
* As the user attempts to minimize the tesselation artifacts by shortening
* segments, then the rotational component will decrease in proportion,
* and the lighting artifact will fall away.
*
* To summarize, there is a slight inexactness in this code. The author
* of the code beleives that this inexactness results in miniscule
* errors in every situation.
*
* Linas Vepstas March 1993
*/
/* ============================================================ */
void draw_angle_style_front_cap (int ncp, /* number of contour points */
gleDouble bi[3], /* biscetor */
gleDouble point_array[][3]) /* polyline */
{
int j;
#ifdef OPENGL_10
GLUtriangulatorObj *tobj;
#endif /* OPENGL_10 */
if (bi[2] < 0.0) {
VEC_SCALE (bi, -1.0, bi);
}
#ifdef GL_32
/* old-style gl handles concave polygons no problem, so the code is
* simple. New-style gl is a lot more tricky. */
/* draw the end cap */
BGNPOLYGON ();
N3F (bi);
for (j=0; j<ncp; j++) {
V3F (point_array[j], j, FRONT_CAP);
}
ENDPOLYGON ();
#endif /* GL_32 */
#ifdef OPENGL_10
N3F(bi);
tobj = gluNewTess ();
gluTessCallback (tobj, GLU_BEGIN, glBegin);
gluTessCallback (tobj, GLU_VERTEX, glVertex3dv);
gluTessCallback (tobj, GLU_END, glEnd);
gluBeginPolygon (tobj);
for (j=0; j<ncp; j++) {
gluTessVertex (tobj, point_array[j], point_array[j]);
}
gluEndPolygon (tobj);
gluDeleteTess (tobj);
#endif /* OPENGL_10 */
}
/* ============================================================ */
void draw_angle_style_back_cap (int ncp, /* number of contour points */
gleDouble bi[3], /* biscetor */
gleDouble point_array[][3]) /* polyline */
{
int j;
#ifdef OPENGL_10
GLUtriangulatorObj *tobj;
#endif /* OPENGL_10 */
if (bi[2] > 0.0) {
VEC_SCALE (bi, -1.0, bi);
}
#ifdef GL_32
/* old-style gl handles concave polygons no problem, so the code is
* simple. New-style gl is a lot more tricky. */
/* draw the end cap */
BGNPOLYGON ();
N3F (bi);
for (j=ncp-1; j>=0; j--) {
V3F (point_array[j], j, BACK_CAP);
}
ENDPOLYGON ();
#endif /* GL_32 */
#ifdef OPENGL_10
N3F (bi);
tobj = gluNewTess ();
gluTessCallback (tobj, GLU_BEGIN, glBegin);
gluTessCallback (tobj, GLU_VERTEX, glVertex3dv);
gluTessCallback (tobj, GLU_END, glEnd);
gluBeginPolygon (tobj);
for (j=ncp-1; j>=0; j--) {
gluTessVertex (tobj, point_array[j], point_array[j]);
}
gluEndPolygon (tobj);
gluDeleteTess (tobj);
#endif /* OPENGL_10 */
}
/* ============================================================ */
void extrusion_angle_join (int ncp, /* number of contour points */
gleDouble contour[][2], /* 2D contour */
gleDouble cont_normal[][2], /* 2D normal vecs */
gleDouble up[3], /* up vector for contour */
int npoints, /* numpoints in poly-line */
gleDouble point_array[][3], /* polyline */
float color_array[][3], /* color of polyline */
gleDouble xform_array[][2][3]) /* 2D contour xforms */
{
int i, j;
int inext, inextnext;
gleDouble m[4][4];
gleDouble len;
gleDouble len_seg;
gleDouble diff[3];
gleDouble bi_0[3], bi_1[3]; /* bisecting plane */
gleDouble bisector_0[3], bisector_1[3]; /* bisecting plane */
gleDouble end_point_0[3], end_point_1[3];
gleDouble origin[3], neg_z[3];
gleDouble yup[3]; /* alternate up vector */
gleDouble *front_loop, *back_loop; /* contours in 3D */
char * mem_anchor;
double *norm_loop;
double *front_norm, *back_norm, *tmp; /* contour normals in 3D */
int first_time;
/* By definition, the contour passed in has its up vector pointing in
* the y direction */
if (up == NULL) {
yup[0] = 0.0;
yup[1] = 1.0;
yup[2] = 0.0;
} else {
VEC_COPY(yup, up);
}
/* ========== "up" vector sanity check ========== */
(void) up_sanity_check (yup, npoints, point_array);
/* the origin is at the origin */
origin [0] = 0.0;
origin [1] = 0.0;
origin [2] = 0.0;
/* and neg_z is at neg z */
neg_z[0] = 0.0;
neg_z[1] = 0.0;
neg_z[2] = 1.0;
/* ignore all segments of zero length */
i = 1;
inext = i;
FIND_NON_DEGENERATE_POINT (inext, npoints, len, diff, point_array);
len_seg = len; /* store for later use */
/* get the bisecting plane */
bisecting_plane (bi_0, point_array[0],
point_array[1],
point_array[inext]);
/* reflect the up vector in the bisecting plane */
VEC_REFLECT (yup, yup, bi_0);
/* malloc the storage we'll need for relaying changed contours to the
* drawing routines. */
mem_anchor = malloc (2 * 3 * ncp * sizeof(double)
+ 2 * 3 * ncp * sizeof(gleDouble));
front_loop = (gleDouble *) mem_anchor;
back_loop = front_loop + 3 * ncp;
front_norm = (double *) (back_loop + 3 * ncp);
back_norm = front_norm + 3 * ncp;
norm_loop = front_norm;
/* may as well get the normals set up now */
if (cont_normal != NULL) {
if (xform_array == NULL) {
for (j=0; j<ncp; j++) {
norm_loop[3*j] = cont_normal[j][0];
norm_loop[3*j+1] = cont_normal[j][1];
norm_loop[3*j+2] = 0.0;
}
} else {
for (j=0; j<ncp; j++) {
NORM_XFORM_2X2 ( (&front_norm[3*j]),
xform_array[inext-1],
cont_normal [j]);
front_norm[3*j+2] = 0.0;
back_norm[3*j+2] = 0.0;
}
}
}
first_time = TRUE;
/* draw tubing, not doing the first segment */
while (inext<npoints-1) {
inextnext = inext;
/* ignore all segments of zero length */
FIND_NON_DEGENERATE_POINT (inextnext, npoints, len, diff, point_array);
/* get the next bisecting plane */
bisecting_plane (bi_1, point_array[i],
point_array[inext],
point_array[inextnext]);
/* rotate so that z-axis points down v2-v1 axis,
* and so that origen is at v1 */
uviewpoint (m, point_array[i], point_array[inext], yup);
PUSHMATRIX ();
MULTMATRIX (m);
/* rotate the bisecting planes into the local coordinate system */
MAT_DOT_VEC_3X3 (bisector_0, m, bi_0);
MAT_DOT_VEC_3X3 (bisector_1, m, bi_1);
neg_z[2] = -len_seg;
/* draw the tube */
/* --------- START OF TMESH GENERATION -------------- */
for (j=0; j<ncp; j++) {
/* if there are normals, and there are either affine xforms, OR
* path-edge normals need to be drawn, then compute local
* coordinate system normals.
*/
if (cont_normal != NULL) {
/* set up the back normals. (The front normals we inherit
* from previous pass through the loop) */
if (xform_array != NULL) {
/* do up the normal vectors with the inverse transpose */
NORM_XFORM_2X2 ( (&back_norm[3*j]),
xform_array[inext],
cont_normal [j]);
}
/* Note that if the xform array is NULL, then normals are
* constant, and are set up outside of the loop.
*/
/*
* if there are normal vectors, and the style calls for it,
* then we want to project the normal vectors into the
* bisecting plane. (This style is needed to make toroids, etc.
* look good: Without this, segmentation artifacts show up
* under lighting.
*/
if (__TUBE_DRAW_PATH_EDGE_NORMALS) {
/* Hmm, if no affine xforms, then we haven't yet set
* back vector. So do it. */
if (xform_array == NULL) {
back_norm[3*j] = cont_normal[j][0];
back_norm[3*j+1] = cont_normal[j][1];
}
/* now, start with a fresh normal (z component equal to
* zero), project onto bisecting plane (by computing
* perpendicular componenet to bisect vector, and renormalize
* (since projected vector is not of unit length */
front_norm[3*j+2] = 0.0;
VEC_PERP ((&front_norm[3*j]), (&front_norm[3*j]), bisector_0);
VEC_NORMALIZE ((&front_norm[3*j]));
back_norm[3*j+2] = 0.0;
VEC_PERP ((&back_norm[3*j]), (&back_norm[3*j]), bisector_1);
VEC_NORMALIZE ((&back_norm[3*j]));
}
}
/* Next, we want to define segements. We find the endpoints of
* the segments by intersecting the contour with the bisecting
* plane. If there is no local affine transform, this is easy.
*
* If there is an affine tranform, then we want to remove the
* torsional component, so that the intersection points won't
* get twisted out of shape. We do this by applying the
* local affine transform to the entire coordinate system.
*/
if (xform_array == NULL) {
end_point_0 [0] = contour[j][0];
end_point_0 [1] = contour[j][1];
end_point_1 [0] = contour[j][0];
end_point_1 [1] = contour[j][1];
} else {
/* transform the contour points with the local xform */
MAT_DOT_VEC_2X3 (end_point_0,
xform_array[inext-1], contour[j]);
MAT_DOT_VEC_2X3 (end_point_1,
xform_array[inext-1], contour[j]);
}
end_point_0 [2] = 0.0;
end_point_1 [2] = - len_seg;
/* The two end-points define a line. Intersect this line
* against the clipping plane defined by the PREVIOUS
* tube segment. */
INNERSECT ((&front_loop[3*j]), /* intersection point (returned) */
origin, /* point on intersecting plane */
bisector_0, /* normal vector to plane */
end_point_0, /* point on line */
end_point_1); /* another point on the line */
/* The two end-points define a line. Intersect this line
* against the clipping plane defined by the NEXT
* tube segment. */
/* if there's an affine coordinate change, be sure to use it */
if (xform_array != NULL) {
/* transform the contour points with the local xform */
MAT_DOT_VEC_2X3 (end_point_0,
xform_array[inext], contour[j]);
MAT_DOT_VEC_2X3 (end_point_1,
xform_array[inext], contour[j]);
}
INNERSECT ((&back_loop[3*j]), /* intersection point (returned) */
neg_z, /* point on intersecting plane */
bisector_1, /* normal vector to plane */
end_point_0, /* point on line */
end_point_1); /* another point on the line */
}
/* --------- END OF TMESH GENERATION -------------- */
/* v^v^v^v^v^v^v^v^v BEGIN END CAPS v^v^v^v^v^v^v^v^v^v^v^v */
/* if end caps are required, draw them. But don't draw any
* but the very first and last caps */
if (__TUBE_DRAW_CAP) {
if (first_time) {
if (color_array != NULL) C3F (color_array[inext-1]);
first_time = FALSE;
draw_angle_style_front_cap (ncp, bisector_0, (gleVector *) front_loop);
}
if (inext == npoints-2) {
if (color_array != NULL) C3F (color_array[inext]);
draw_angle_style_back_cap (ncp, bisector_1, (gleVector *) back_loop);
}
}
/* v^v^v^v^v^v^v^v^v END END CAPS v^v^v^v^v^v^v^v^v^v^v^v */
/* |||||||||||||||||| START SEGMENT DRAW |||||||||||||||||||| */
/* There are six different cases we can have for presence and/or
* absecnce of colors and normals, and for interpretation of
* normals. The blechy set of nested if statements below
* branch to each of the six cases */
if ((xform_array == NULL) && (!__TUBE_DRAW_PATH_EDGE_NORMALS)) {
if (color_array == NULL) {
if (cont_normal == NULL) {
draw_segment_plain (ncp, (gleVector *) front_loop,
(gleVector *) back_loop, inext, len_seg);
} else
if (__TUBE_DRAW_FACET_NORMALS) {
draw_segment_facet_n (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) norm_loop, inext, len_seg);
} else {
draw_segment_edge_n (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) norm_loop, inext, len_seg);
}
} else {
if (cont_normal == NULL) {
draw_segment_color (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
color_array[inext-1],
color_array[inext], inext, len_seg);
} else
if (__TUBE_DRAW_FACET_NORMALS) {
draw_segment_c_and_facet_n (ncp,
(gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) norm_loop,
color_array[inext-1],
color_array[inext], inext, len_seg);
} else {
draw_segment_c_and_edge_n (ncp,
(gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) norm_loop,
color_array[inext-1],
color_array[inext], inext, len_seg);
}
}
} else {
if (color_array == NULL) {
if (cont_normal == NULL) {
draw_segment_plain (ncp, (gleVector *) front_loop,
(gleVector *) back_loop, inext, len_seg);
} else
if (__TUBE_DRAW_FACET_NORMALS) {
draw_binorm_segment_facet_n (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) front_norm,
(gleVector *) back_norm,
inext, len_seg);
} else {
draw_binorm_segment_edge_n (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) front_norm,
(gleVector *) back_norm,
inext, len_seg);
}
} else {
if (cont_normal == NULL) {
draw_segment_color (ncp, (gleVector *) front_loop,
(gleVector *) back_loop,
color_array[inext-1],
color_array[inext], inext, len_seg);
} else
if (__TUBE_DRAW_FACET_NORMALS) {
draw_binorm_segment_c_and_facet_n (ncp,
(gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) front_norm,
(gleVector *) back_norm,
color_array[inext-1],
color_array[inext], inext, len_seg);
} else {
draw_binorm_segment_c_and_edge_n (ncp,
(gleVector *) front_loop,
(gleVector *) back_loop,
(gleVector *) front_norm,
(gleVector *) back_norm,
color_array[inext-1],
color_array[inext], inext, len_seg);
}
}
}
/* |||||||||||||||||| END SEGMENT DRAW |||||||||||||||||||| */
/* pop this matrix, do the next set */
POPMATRIX ();
/* bump everything to the next vertex */
len_seg = len;
i = inext;
inext = inextnext;
VEC_COPY (bi_0, bi_1);
/* trade norm loops */
tmp = front_norm;
front_norm = back_norm;
back_norm = tmp;
/* reflect the up vector in the bisecting plane */
VEC_REFLECT (yup, yup, bi_0);
}
/* be sure to free it all up */
free (mem_anchor);
}
/* ============================================================ */
|
