405 lines
12 KiB
C
405 lines
12 KiB
C
|
/*
|
||
|
|
** Copyright 1991, Silicon Graphics, Inc.
|
||
|
|
** All Rights Reserved.
|
||
|
|
**
|
||
|
|
** This is UNPUBLISHED PROPRIETARY SOURCE CODE of Silicon Graphics, Inc.;
|
||
|
|
** the contents of this file may not be disclosed to third parties, copied or
|
||
|
|
** duplicated in any form, in whole or in part, without the prior written
|
||
|
|
** permission of Silicon Graphics, Inc.
|
||
|
|
**
|
||
|
|
** RESTRICTED RIGHTS LEGEND:
|
||
|
|
** Use, duplication or disclosure by the Government is subject to restrictions
|
||
|
|
** as set forth in subdivision (c)(1)(ii) of the Rights in Technical Data
|
||
|
|
** and Computer Software clause at DFARS 252.227-7013, and/or in similar or
|
||
|
|
** successor clauses in the FAR, DOD or NASA FAR Supplement. Unpublished -
|
||
|
|
** rights reserved under the Copyright Laws of the United States.
|
||
|
|
*/
|
||
|
|
#include "precomp.h"
|
||
|
|
#pragma hdrstop
|
||
|
|
|
||
|
|
/*
|
||
|
|
** The following is a discussion of the math used to do edge clipping against
|
||
|
|
** a clipping plane.
|
||
|
|
**
|
||
|
|
** P1 is an end point of the edge
|
||
|
|
** P2 is the other end point of the edge
|
||
|
|
**
|
||
|
|
** Q = t*P1 + (1 - t)*P2
|
||
|
|
** That is, Q lies somewhere on the line formed by P1 and P2.
|
||
|
|
**
|
||
|
|
** 0 <= t <= 1
|
||
|
|
** This constrains Q to lie between P1 and P2.
|
||
|
|
**
|
||
|
|
** C is the plane equation for the clipping plane
|
||
|
|
**
|
||
|
|
** D1 = P1 dot C
|
||
|
|
** D1 is the distance between P1 and C. If P1 lies on the plane
|
||
|
|
** then D1 will be zero. The sign of D1 will determine which side
|
||
|
|
** of the plane that P1 is on, with negative being outside.
|
||
|
|
**
|
||
|
|
** D2 = P2 dot C
|
||
|
|
** D2 is the distance between P2 and C. If P2 lies on the plane
|
||
|
|
** then D2 will be zero. The sign of D2 will determine which side
|
||
|
|
** of the plane that P2 is on, with negative being outside.
|
||
|
|
**
|
||
|
|
** Because we are trying to find the intersection of the P1 P2 line
|
||
|
|
** segment with the clipping plane we require that:
|
||
|
|
**
|
||
|
|
** Q dot C = 0
|
||
|
|
**
|
||
|
|
** Therefore
|
||
|
|
**
|
||
|
|
** (t*P1 + (1 - t)*P2) dot C = 0
|
||
|
|
**
|
||
|
|
** (t*P1 + P2 - t*P2) dot C = 0
|
||
|
|
**
|
||
|
|
** t*P1 dot C + P2 dot C - t*P2 dot C = 0
|
||
|
|
**
|
||
|
|
** Substituting D1 and D2 in
|
||
|
|
**
|
||
|
|
** t*D1 + D2 - t*D2 = 0
|
||
|
|
**
|
||
|
|
** Solving for t
|
||
|
|
**
|
||
|
|
** t = -D2 / (D1 - D2)
|
||
|
|
**
|
||
|
|
** t = D2 / (D2 - D1)
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
** Clip a line against the frustum clip planes and any user clipping planes.
|
||
|
|
** If an edge remains after clipping then compute the window coordinates
|
||
|
|
** and invoke the renderer.
|
||
|
|
**
|
||
|
|
** Notice: This algorithim is an example of an implementation that is
|
||
|
|
** different than what the spec says. This is equivalent in functionality
|
||
|
|
** and meets the spec, but doesn't clip in eye space. This clipper clips
|
||
|
|
** in NTVP (clip) space.
|
||
|
|
**
|
||
|
|
** Trivial accept/reject has already been dealt with.
|
||
|
|
*/
|
||
|
|
#ifdef NT
|
||
|
|
void FASTCALL __glClipLine(__GLcontext *gc, __GLvertex *a, __GLvertex *b,
|
||
|
|
GLuint flags)
|
||
|
|
#else
|
||
|
|
void __glClipLine(__GLcontext *gc, __GLvertex *a, __GLvertex *b)
|
||
|
|
#endif
|
||
|
|
{
|
||
|
|
#ifdef NT
|
||
|
|
__GLvertex *provokingA = a;
|
||
|
|
__GLvertex *provokingB = b;
|
||
|
|
#else
|
||
|
|
__GLvertex *provoking = b;
|
||
|
|
#endif
|
||
|
|
__GLvertex np1, np2;
|
||
|
|
__GLcoord *plane;
|
||
|
|
GLuint needs, allClipCodes, clipCodes;
|
||
|
|
PFN_VERTEX_CLIP_PROC clip;
|
||
|
|
__GLfloat zero;
|
||
|
|
__GLfloat winx, winy;
|
||
|
|
__GLfloat vpXCenter, vpYCenter, vpZCenter;
|
||
|
|
__GLfloat vpXScale, vpYScale, vpZScale;
|
||
|
|
__GLviewport *vp;
|
||
|
|
__GLfloat x, y, z, wInv;
|
||
|
|
GLint i;
|
||
|
|
|
||
|
|
// We have to turn rounding on. Otherwise, the fast FP-comparison
|
||
|
|
// routines below can fail:
|
||
|
|
FPU_SAVE_MODE();
|
||
|
|
FPU_ROUND_ON_PREC_HI();
|
||
|
|
|
||
|
|
/* Check for trivial pass of the line */
|
||
|
|
allClipCodes = a->clipCode | b->clipCode;
|
||
|
|
|
||
|
|
/*
|
||
|
|
** For each clippling plane that something is out on, clip
|
||
|
|
** check the verticies. Note that no bits will be set in
|
||
|
|
** allClipCodes for clip planes that are not enabled.
|
||
|
|
*/
|
||
|
|
zero = __glZero;
|
||
|
|
clip = gc->procs.lineClipParam;
|
||
|
|
|
||
|
|
/*
|
||
|
|
** Do user clip planes first, because we will maintain eye coordinates
|
||
|
|
** only while doing user clip planes. They are ignored for the
|
||
|
|
** frustum clipping planes.
|
||
|
|
*/
|
||
|
|
clipCodes = allClipCodes >> 6;
|
||
|
|
if (clipCodes) {
|
||
|
|
plane = &gc->state.transform.eyeClipPlanes[0];
|
||
|
|
do {
|
||
|
|
/*
|
||
|
|
** See if this clip plane has anything out of it. If not,
|
||
|
|
** press onward to check the next plane. Note that we
|
||
|
|
** shift this mask to the right at the bottom of the loop.
|
||
|
|
*/
|
||
|
|
if (clipCodes & 1) {
|
||
|
|
__GLfloat t, d1, d2;
|
||
|
|
|
||
|
|
d1 = (plane->x * ((POLYDATA *)a)->eye.x) +
|
||
|
|
(plane->y * ((POLYDATA *)a)->eye.y) +
|
||
|
|
(plane->z * ((POLYDATA *)a)->eye.z) +
|
||
|
|
(plane->w * ((POLYDATA *)a)->eye.w);
|
||
|
|
d2 = (plane->x * ((POLYDATA *)b)->eye.x) +
|
||
|
|
(plane->y * ((POLYDATA *)b)->eye.y) +
|
||
|
|
(plane->z * ((POLYDATA *)b)->eye.z) +
|
||
|
|
(plane->w * ((POLYDATA *)b)->eye.w);
|
||
|
|
if (__GL_FLOAT_LTZ(d1)) {
|
||
|
|
/* a is out */
|
||
|
|
if (__GL_FLOAT_LTZ(d2)) {
|
||
|
|
/* a & b are out */
|
||
|
|
FPU_RESTORE_MODE();
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
** A is out and B is in. Compute new A coordinate
|
||
|
|
** clipped to the plane.
|
||
|
|
*/
|
||
|
|
t = d2 / (d2 - d1);
|
||
|
|
(*clip)(&np1, a, b, t);
|
||
|
|
((POLYDATA *)&np1)->eye.x =
|
||
|
|
t*(((POLYDATA *)a)->eye.x - ((POLYDATA *)b)->eye.x) +
|
||
|
|
((POLYDATA *)b)->eye.x;
|
||
|
|
((POLYDATA *)&np1)->eye.y =
|
||
|
|
t*(((POLYDATA *)a)->eye.y - ((POLYDATA *)b)->eye.y) +
|
||
|
|
((POLYDATA *)b)->eye.y;
|
||
|
|
((POLYDATA *)&np1)->eye.z =
|
||
|
|
t*(((POLYDATA *)a)->eye.z - ((POLYDATA *)b)->eye.z) +
|
||
|
|
((POLYDATA *)b)->eye.z;
|
||
|
|
((POLYDATA *)&np1)->eye.w =
|
||
|
|
t*(((POLYDATA *)a)->eye.w - ((POLYDATA *)b)->eye.w) +
|
||
|
|
((POLYDATA *)b)->eye.w;
|
||
|
|
a = &np1;
|
||
|
|
a->has = b->has;
|
||
|
|
ASSERTOPENGL(!(a->has & __GL_HAS_FIXEDPT), "clear __GL_HAS_FIXEDPT flag!\n");
|
||
|
|
} else {
|
||
|
|
/* a is in */
|
||
|
|
if (__GL_FLOAT_LTZ(d2)) {
|
||
|
|
/*
|
||
|
|
** A is in and B is out. Compute new B
|
||
|
|
** coordinate clipped to the plane.
|
||
|
|
**
|
||
|
|
** NOTE: To avoid cracking in polygons with
|
||
|
|
** shared clipped edges we always compute "t"
|
||
|
|
** from the out vertex to the in vertex. The
|
||
|
|
** above clipping code gets this for free (b is
|
||
|
|
** in and a is out). In this code b is out and a
|
||
|
|
** is in, so we reverse the t computation and the
|
||
|
|
** argument order to (*clip).
|
||
|
|
*/
|
||
|
|
t = d1 / (d1 - d2);
|
||
|
|
(*clip)(&np2, b, a, t);
|
||
|
|
((POLYDATA *)&np2)->eye.x =
|
||
|
|
t*(((POLYDATA *)b)->eye.x - ((POLYDATA *)a)->eye.x)+
|
||
|
|
((POLYDATA *)a)->eye.x;
|
||
|
|
((POLYDATA *)&np2)->eye.y =
|
||
|
|
t*(((POLYDATA *)b)->eye.y - ((POLYDATA *)a)->eye.y)+
|
||
|
|
((POLYDATA *)a)->eye.y;
|
||
|
|
((POLYDATA *)&np2)->eye.z =
|
||
|
|
t*(((POLYDATA *)b)->eye.z - ((POLYDATA *)a)->eye.z)+
|
||
|
|
((POLYDATA *)a)->eye.z;
|
||
|
|
((POLYDATA *)&np2)->eye.w =
|
||
|
|
t*(((POLYDATA *)b)->eye.w - ((POLYDATA *)a)->eye.w)+
|
||
|
|
((POLYDATA *)a)->eye.w;
|
||
|
|
b = &np2;
|
||
|
|
b->has = a->has;
|
||
|
|
ASSERTOPENGL(!(b->has & __GL_HAS_FIXEDPT), "clear __GL_HAS_FIXEDPT flag!\n");
|
||
|
|
} else {
|
||
|
|
/* A and B are in */
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
plane++;
|
||
|
|
clipCodes >>= 1;
|
||
|
|
} while (clipCodes);
|
||
|
|
}
|
||
|
|
|
||
|
|
allClipCodes &= __GL_FRUSTUM_CLIP_MASK;
|
||
|
|
if (allClipCodes) {
|
||
|
|
i = 0;
|
||
|
|
do {
|
||
|
|
/*
|
||
|
|
** See if this clip plane has anything out of it. If not,
|
||
|
|
** press onward to check the next plane. Note that we
|
||
|
|
** shift this mask to the right at the bottom of the loop.
|
||
|
|
*/
|
||
|
|
if (allClipCodes & 1) {
|
||
|
|
__GLfloat t, d1, d2;
|
||
|
|
|
||
|
|
if (i & 1)
|
||
|
|
{
|
||
|
|
d1 = a->clip.w -
|
||
|
|
*(__GLfloat *)((GLubyte *)a + __glFrustumOffsets[i]);
|
||
|
|
d2 = b->clip.w -
|
||
|
|
*(__GLfloat *)((GLubyte *)b + __glFrustumOffsets[i]);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
d1 = *(__GLfloat *)((GLubyte *)a + __glFrustumOffsets[i]) +
|
||
|
|
a->clip.w;
|
||
|
|
d2 = *(__GLfloat *)((GLubyte *)b + __glFrustumOffsets[i]) +
|
||
|
|
b->clip.w;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (__GL_FLOAT_LTZ(d1)) {
|
||
|
|
/* a is out */
|
||
|
|
if (__GL_FLOAT_LTZ(d2)) {
|
||
|
|
/* a & b are out */
|
||
|
|
FPU_RESTORE_MODE();
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
** A is out and B is in. Compute new A coordinate
|
||
|
|
** clipped to the plane.
|
||
|
|
*/
|
||
|
|
t = d2 / (d2 - d1);
|
||
|
|
(*clip)(&np1, a, b, t);
|
||
|
|
a = &np1;
|
||
|
|
a->has = b->has;
|
||
|
|
ASSERTOPENGL(!(a->has & __GL_HAS_FIXEDPT), "clear __GL_HAS_FIXEDPT flag!\n");
|
||
|
|
} else {
|
||
|
|
/* a is in */
|
||
|
|
if (__GL_FLOAT_LTZ(d2)) {
|
||
|
|
/*
|
||
|
|
** A is in and B is out. Compute new B
|
||
|
|
** coordinate clipped to the plane.
|
||
|
|
**
|
||
|
|
** NOTE: To avoid cracking in polygons with
|
||
|
|
** shared clipped edges we always compute "t"
|
||
|
|
** from the out vertex to the in vertex. The
|
||
|
|
** above clipping code gets this for free (b is
|
||
|
|
** in and a is out). In this code b is out and a
|
||
|
|
** is in, so we reverse the t computation and the
|
||
|
|
** argument order to (*clip).
|
||
|
|
*/
|
||
|
|
t = d1 / (d1 - d2);
|
||
|
|
(*clip)(&np2, b, a, t);
|
||
|
|
b = &np2;
|
||
|
|
b->has = a->has;
|
||
|
|
ASSERTOPENGL(!(b->has & __GL_HAS_FIXEDPT), "clear __GL_HAS_FIXEDPT flag!\n");
|
||
|
|
} else {
|
||
|
|
/* A and B are in */
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
i++;
|
||
|
|
allClipCodes >>= 1;
|
||
|
|
} while (allClipCodes);
|
||
|
|
}
|
||
|
|
|
||
|
|
vp = &gc->state.viewport;
|
||
|
|
vpXCenter = vp->xCenter;
|
||
|
|
vpYCenter = vp->yCenter;
|
||
|
|
vpZCenter = vp->zCenter;
|
||
|
|
vpXScale = vp->xScale;
|
||
|
|
vpYScale = vp->yScale;
|
||
|
|
vpZScale = vp->zScale;
|
||
|
|
|
||
|
|
/* Compute window coordinates for vertices generated by clipping */
|
||
|
|
if (provokingA->clipCode != 0)
|
||
|
|
{
|
||
|
|
wInv = __glOne / a->clip.w;
|
||
|
|
x = a->clip.x;
|
||
|
|
y = a->clip.y;
|
||
|
|
z = a->clip.z;
|
||
|
|
winx = x * vpXScale * wInv + vpXCenter;
|
||
|
|
winy = y * vpYScale * wInv + vpYCenter;
|
||
|
|
|
||
|
|
if (winx < gc->transform.fminx)
|
||
|
|
winx = gc->transform.fminx;
|
||
|
|
else if (winx >= gc->transform.fmaxx)
|
||
|
|
winx = gc->transform.fmaxx - gc->constants.viewportEpsilon;
|
||
|
|
|
||
|
|
if (winy < gc->transform.fminy)
|
||
|
|
winy = gc->transform.fminy;
|
||
|
|
else if (winy >= gc->transform.fmaxy)
|
||
|
|
winy = gc->transform.fmaxy - gc->constants.viewportEpsilon;
|
||
|
|
|
||
|
|
a->window.z = z * vpZScale * wInv + vpZCenter;
|
||
|
|
a->window.w = wInv;
|
||
|
|
a->window.x = winx;
|
||
|
|
a->window.y = winy;
|
||
|
|
|
||
|
|
// Update color pointer since this vertex is a new one
|
||
|
|
// generated by clipping
|
||
|
|
if (gc->state.light.shadingModel == GL_FLAT)
|
||
|
|
{
|
||
|
|
a->color = &provokingA->colors[__GL_FRONTFACE];
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
a->color = &a->colors[__GL_FRONTFACE];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (provokingB->clipCode != 0)
|
||
|
|
{
|
||
|
|
wInv = __glOne / b->clip.w;
|
||
|
|
x = b->clip.x;
|
||
|
|
y = b->clip.y;
|
||
|
|
z = b->clip.z;
|
||
|
|
winx = x * vpXScale * wInv + vpXCenter;
|
||
|
|
winy = y * vpYScale * wInv + vpYCenter;
|
||
|
|
|
||
|
|
if (winx < gc->transform.fminx)
|
||
|
|
winx = gc->transform.fminx;
|
||
|
|
else if (winx >= gc->transform.fmaxx)
|
||
|
|
winx = gc->transform.fmaxx - gc->constants.viewportEpsilon;
|
||
|
|
|
||
|
|
if (winy < gc->transform.fminy)
|
||
|
|
winy = gc->transform.fminy;
|
||
|
|
else if (winy >= gc->transform.fmaxy)
|
||
|
|
winy = gc->transform.fmaxy - gc->constants.viewportEpsilon;
|
||
|
|
|
||
|
|
b->window.z = z * vpZScale * wInv + vpZCenter;
|
||
|
|
b->window.w = wInv;
|
||
|
|
b->window.x = winx;
|
||
|
|
b->window.y = winy;
|
||
|
|
|
||
|
|
if (gc->state.light.shadingModel == GL_FLAT)
|
||
|
|
{
|
||
|
|
b->color = &provokingB->colors[__GL_FRONTFACE];
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b->color = &b->colors[__GL_FRONTFACE];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Restore the floating-point mode for rendering:
|
||
|
|
FPU_RESTORE_MODE();
|
||
|
|
|
||
|
|
/* Validate line state */
|
||
|
|
if (gc->state.light.shadingModel == GL_FLAT) {
|
||
|
|
// Add the vertices then restore the b color pointer
|
||
|
|
//
|
||
|
|
// Note that although b is the only new vertex, up
|
||
|
|
// to two vertices can be added because each new vertex
|
||
|
|
// generated by clipping must be added. For a line where
|
||
|
|
// both endpoints are out of the clipping region, both
|
||
|
|
// an entry and an exit vertex must be added
|
||
|
|
if (provokingA->clipCode != 0)
|
||
|
|
{
|
||
|
|
// a was out so a new vertex was added at the point of
|
||
|
|
// entry
|
||
|
|
flags |= __GL_LVERT_FIRST;
|
||
|
|
}
|
||
|
|
// b is always added since either:
|
||
|
|
// b was in and is new so it needs to be added
|
||
|
|
// b was out so a new vertex was added at the exit point
|
||
|
|
(*gc->procs.renderLine)(gc, a, b, flags);
|
||
|
|
|
||
|
|
#ifndef NT
|
||
|
|
b->color = &b->colors[__GL_FRONTFACE];
|
||
|
|
#endif
|
||
|
|
} else {
|
||
|
|
if (provokingA->clipCode != 0)
|
||
|
|
{
|
||
|
|
flags |= __GL_LVERT_FIRST;
|
||
|
|
}
|
||
|
|
(*gc->procs.renderLine)(gc, a, b, flags);
|
||
|
|
}
|
||
|
|
}
|