/******************************Module*Header*******************************\
* Module Name: mcdclip.c
*
* Contains the line and polygon clipping routines for an MCD driver.
*
* Copyright (c) 1996 Microsoft Corporation
\**************************************************************************/
#include "precomp.h"
#include "mcdhw.h"
#include "mcdutil.h"
#include "mcdmath.h"
MCDCOORD __MCD_frustumClipPlanes[6] = {
{(MCDFLOAT) 1.0, (MCDFLOAT) 0.0, (MCDFLOAT) 0.0, (MCDFLOAT) 1.0 }, // left
{(MCDFLOAT)-1.0, (MCDFLOAT) 0.0, (MCDFLOAT) 0.0, (MCDFLOAT) 1.0 }, // right
{(MCDFLOAT) 0.0, (MCDFLOAT) 1.0, (MCDFLOAT) 0.0, (MCDFLOAT) 1.0 }, // bottom
{(MCDFLOAT) 0.0, (MCDFLOAT)-1.0, (MCDFLOAT) 0.0, (MCDFLOAT) 1.0 }, // top
{(MCDFLOAT) 0.0, (MCDFLOAT) 0.0, (MCDFLOAT) 1.0, (MCDFLOAT) 1.0 }, // zNear
{(MCDFLOAT) 0.0, (MCDFLOAT) 0.0, (MCDFLOAT)-1.0, (MCDFLOAT) 1.0 }, // zFar
};
////////////////////////////////////////////////////////////////////////
// Clipping macros used to build clip functions below.
////////////////////////////////////////////////////////////////////////
#define __MCD_CLIP_POS(v, a, b, t) \
v->clipCoord.x = t*(a->clipCoord.x - b->clipCoord.x) + b->clipCoord.x; \
v->clipCoord.y = t*(a->clipCoord.y - b->clipCoord.y) + b->clipCoord.y; \
v->clipCoord.z = t*(a->clipCoord.z - b->clipCoord.z) + b->clipCoord.z; \
v->clipCoord.w = t*(a->clipCoord.w - b->clipCoord.w) + b->clipCoord.w
// Note that we compute the values needed for both "cheap" fog only...
#define __MCD_CLIP_FOG(v, a, b, t) \
v->fog = t * (a->fog - b->fog) + b->fog;
#define __MCD_CLIP_COLOR(v, a, b, t) \
v->colors[__MCD_FRONTFACE].r = t*(a->colors[__MCD_FRONTFACE].r \
- b->colors[__MCD_FRONTFACE].r) + b->colors[__MCD_FRONTFACE].r; \
v->colors[__MCD_FRONTFACE].g = t*(a->colors[__MCD_FRONTFACE].g \
- b->colors[__MCD_FRONTFACE].g) + b->colors[__MCD_FRONTFACE].g; \
v->colors[__MCD_FRONTFACE].b = t*(a->colors[__MCD_FRONTFACE].b \
- b->colors[__MCD_FRONTFACE].b) + b->colors[__MCD_FRONTFACE].b; \
v->colors[__MCD_FRONTFACE].a = t*(a->colors[__MCD_FRONTFACE].a \
- b->colors[__MCD_FRONTFACE].a) + b->colors[__MCD_FRONTFACE].a
#define __MCD_CLIP_BACKCOLOR(v, a, b, t) \
v->colors[__MCD_BACKFACE].r = t*(a->colors[__MCD_BACKFACE].r \
- b->colors[__MCD_BACKFACE].r) + b->colors[__MCD_BACKFACE].r; \
v->colors[__MCD_BACKFACE].g = t*(a->colors[__MCD_BACKFACE].g \
- b->colors[__MCD_BACKFACE].g) + b->colors[__MCD_BACKFACE].g; \
v->colors[__MCD_BACKFACE].b = t*(a->colors[__MCD_BACKFACE].b \
- b->colors[__MCD_BACKFACE].b) + b->colors[__MCD_BACKFACE].b; \
v->colors[__MCD_BACKFACE].a = t*(a->colors[__MCD_BACKFACE].a \
- b->colors[__MCD_BACKFACE].a) + b->colors[__MCD_BACKFACE].a
#define __MCD_CLIP_INDEX(v, a, b, t) \
v->colors[__MCD_FRONTFACE].r = t*(a->colors[__MCD_FRONTFACE].r \
- b->colors[__MCD_FRONTFACE].r) + b->colors[__MCD_FRONTFACE].r
#define __MCD_CLIP_BACKINDEX(v, a, b, t) \
v->colors[__MCD_BACKFACE].r = t*(a->colors[__MCD_BACKFACE].r \
- b->colors[__MCD_BACKFACE].r) + b->colors[__MCD_BACKFACE].r
#define __MCD_CLIP_TEXTURE(v, a, b, t) \
v->texCoord.x = t*(a->texCoord.x - b->texCoord.x) + b->texCoord.x; \
v->texCoord.y = t*(a->texCoord.y - b->texCoord.y) + b->texCoord.y;
#ifdef CLIP_TEXTURE_XFORM
v->texCoord.z = t*(a->texCoord.z - b->texCoord.z) + b->texCoord.z; \
v->texCoord.w = t*(a->texCoord.w - b->texCoord.w) + b->texCoord.w
#endif
////////////////////////////////////////////////////////////////////////
// Clipping functions to clip vertices:
////////////////////////////////////////////////////////////////////////
static VOID FASTCALL Clip(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
}
static VOID FASTCALL ClipC(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
}
static VOID FASTCALL ClipI(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
}
static VOID FASTCALL ClipBC(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_BACKCOLOR(dst,a,b,t);
}
static VOID FASTCALL ClipBI(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_BACKINDEX(dst,a,b,t);
}
static VOID FASTCALL ClipT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipIT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipBIT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_BACKINDEX(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipCT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipBCT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_BACKCOLOR(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipF(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
}
static VOID FASTCALL ClipIF(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
}
static VOID FASTCALL ClipCF(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
}
static VOID FASTCALL ClipBCF(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_BACKCOLOR(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
}
static VOID FASTCALL ClipBIF(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_BACKINDEX(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
}
static VOID FASTCALL ClipFT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipIFT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipBIFT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_INDEX(dst,a,b,t);
__MCD_CLIP_BACKINDEX(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipCFT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID FASTCALL ClipBCFT(MCDVERTEX *dst, const MCDVERTEX *a,
const MCDVERTEX *b, MCDFLOAT t)
{
__MCD_CLIP_POS(dst,a,b,t);
__MCD_CLIP_COLOR(dst,a,b,t);
__MCD_CLIP_BACKCOLOR(dst,a,b,t);
__MCD_CLIP_FOG(dst,a,b,t);
__MCD_CLIP_TEXTURE(dst,a,b,t);
}
static VOID (FASTCALL *clipProcs[20])(MCDVERTEX*, const MCDVERTEX*,
const MCDVERTEX*, MCDFLOAT) =
{
Clip, ClipI, ClipC, ClipBI, ClipBC,
ClipF, ClipIF, ClipCF, ClipBIF, ClipBCF,
ClipT, ClipIT, ClipCT, ClipBIT, ClipBCT,
ClipFT, ClipIFT, ClipCFT, ClipBIFT, ClipBCFT,
};
VOID FASTCALL __MCDPickClipFuncs(DEVRC *pRc)
{
LONG line = 0, poly = 0;
BOOL twoSided = (pRc->MCDState.enables & MCD_LIGHTING_ENABLE) &&
(pRc->MCDState.twoSided);
if (pRc->bRGBMode) {
if (pRc->MCDState.shadeModel != GL_FLAT) {
line = 2;
poly = (twoSided ? 4 : 2);
}
} else {
if (pRc->MCDState.shadeModel != GL_FLAT) {
line = 1;
poly = (twoSided ? 3 : 1);
}
}
if ((pRc->bCheapFog) && !(pRc->MCDState.shadeModel == GL_SMOOTH)) {
{
line += 5;
poly += 5;
}
}
if (pRc->MCDState.textureEnabled) {
line += 10;
poly += 10;
}
pRc->lineClipParam = clipProcs[line];
pRc->polyClipParam = clipProcs[poly];
}
////////////////////////////////////////////////////////////////////////
// The real primitive clippers:
////////////////////////////////////////////////////////////////////////
/*
** 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)
*/
static LONG clipToPlane(DEVRC *pRc, MCDVERTEX **iv, LONG niv,
MCDVERTEX **ov, MCDCOORD *plane)
{
LONG i, nout, generated;
MCDVERTEX *s, *p, *newVertex, *temp;
MCDFLOAT pDist, sDist, t;
MCDFLOAT zero = ZERO;
VOID (FASTCALL *clip)(MCDVERTEX*, const MCDVERTEX*, const MCDVERTEX*, MCDFLOAT);
nout = 0;
generated = 0;
temp = pRc->pNextClipTemp;
clip = pRc->polyClipParam;
s = iv[niv-1];
sDist = (s->clipCoord.x * plane->x) + (s->clipCoord.y * plane->y) +
(s->clipCoord.z * plane->z) + (s->clipCoord.w * plane->w);
for (i = 0; i < niv; i++) {
p = iv[i];
pDist = (p->clipCoord.x * plane->x) + (p->clipCoord.y * plane->y) +
(p->clipCoord.z * plane->z) + (p->clipCoord.w * plane->w);
if (pDist >= zero) {
/* p is inside the clipping plane half space */
if (sDist >= zero) {
/* s is inside the clipping plane half space */
*ov++ = p;
nout++;
} else {
/* s is outside the clipping plane half space */
t = pDist / (pDist - sDist);
newVertex = temp++;
(*clip)(newVertex, s, p, t);
newVertex->flags = s->flags;
newVertex->clipCode = s->clipCode;
*ov++ = newVertex;
*ov++ = p;
nout += 2;
if (++generated >= 3) {
/* Toss the non-convex polygon */
return 0;
}
}
} else {
/* p is outside the clipping plane half space */
if (sDist >= zero) {
/*
** s is inside the clipping plane half space
**
** 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 (p is in and s is out). In this code p
** is out and s is in, so we reverse the t computation
** and the argument order to __MCDDoClip.
*/
t = sDist / (sDist - pDist);
newVertex = temp++;
(*clip)(newVertex, p, s, t);
newVertex->flags = s->flags | MCDVERTEX_EDGEFLAG;
newVertex->clipCode = p->clipCode;
*ov++ = newVertex;
nout++;
if (++generated >= 3) {
/* Toss the non-convex polygon */
return 0;
}
} else {
/* both points are outside */
}
}
s = p;
sDist = pDist;
}
pRc->pNextClipTemp = temp;
return nout;
}
/*
** Identical to clipToPlane(), except that the clipping is done in eye
** space.
*/
static LONG clipToPlaneEye(DEVRC *pRc, MCDVERTEX **iv, LONG niv,
MCDVERTEX **ov, MCDCOORD *plane)
{
LONG i, nout, generated;
MCDVERTEX *s, *p, *newVertex, *temp;
MCDFLOAT pDist, sDist, t;
MCDFLOAT zero = __MCDZERO;
VOID (FASTCALL *clip)(MCDVERTEX*, const MCDVERTEX*, const MCDVERTEX*, MCDFLOAT);
nout = 0;
generated = 0;
temp = pRc->pNextClipTemp;
clip = pRc->polyClipParam;
s = iv[niv-1];
sDist = (s->eyeCoord.x * plane->x) +
(s->eyeCoord.y * plane->y) +
(s->eyeCoord.z * plane->z) +
(s->eyeCoord.w * plane->w);
for (i = 0; i < niv; i++) {
p = iv[i];
pDist = (p->eyeCoord.x * plane->x) +
(p->eyeCoord.y * plane->y) +
(p->eyeCoord.z * plane->z) +
(p->eyeCoord.w * plane->w);
if (pDist >= zero) {
/* p is inside the clipping plane half space */
if (sDist >= zero) {
/* s is inside the clipping plane half space */
*ov++ = p;
nout++;
} else {
/* s is outside the clipping plane half space */
t = pDist / (pDist - sDist);
newVertex = temp++;
(*clip)(newVertex, s, p, t);
newVertex->eyeCoord.x = t*(s->eyeCoord.x - p->eyeCoord.x) + p->eyeCoord.x;
newVertex->eyeCoord.y = t*(s->eyeCoord.y - p->eyeCoord.y) + p->eyeCoord.y;
newVertex->eyeCoord.z = t*(s->eyeCoord.z - p->eyeCoord.z) + p->eyeCoord.z;
newVertex->eyeCoord.w = t*(s->eyeCoord.w - p->eyeCoord.w) + p->eyeCoord.w;
newVertex->flags = s->flags;
newVertex->clipCode = s->clipCode; //!!!!
*ov++ = newVertex;
*ov++ = p;
nout += 2;
if (++generated >= 3) {
/* Toss the non-convex polygon */
return 0;
}
}
} else {
/* p is outside the clipping plane half space */
if (sDist >= zero) {
/*
** s is inside the clipping plane half space
**
** 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 (p is in and s is out). In this code p
** is out and s is in, so we reverse the t computation
** and the argument order to __MCDDoClip.
*/
t = sDist / (sDist - pDist);
newVertex = temp++;
(*clip)(newVertex, p, s, t);
newVertex->eyeCoord.x = t*(p->eyeCoord.x - s->eyeCoord.x) + s->eyeCoord.x;
newVertex->eyeCoord.y = t*(p->eyeCoord.y - s->eyeCoord.y) + s->eyeCoord.y;
newVertex->eyeCoord.z = t*(p->eyeCoord.z - s->eyeCoord.z) + s->eyeCoord.z;
newVertex->eyeCoord.w = t*(p->eyeCoord.w - s->eyeCoord.w) + s->eyeCoord.w;
newVertex->flags = s->flags | MCDVERTEX_EDGEFLAG;
newVertex->clipCode = p->clipCode;
*ov++ = newVertex;
nout++;
if (++generated >= 3) {
/* Toss the non-convex polygon */
return 0;
}
} else {
/* both points are outside */
}
}
s = p;
sDist = pDist;
}
pRc->pNextClipTemp = temp;
return nout;
}
/*
** Each clipping plane can add at most one vertex to a convex polygon (it may
** remove up to all of the vertices). The clipping will leave a polygon
** convex. Because of this the maximum number of verticies output from
** the clipToPlane procedure will be total number of clip planes (assuming
** each plane adds one new vertex) plus the original number of verticies
** (3 since this if for triangles).
*/
#define __MCD_TOTAL_CLIP_PLANES 6 + MCD_MAX_USER_CLIP_PLANES
#define __MCD_MAX_POLYGON_CLIP_SIZE 256
#define __MCD_MAX_CLIP_VERTEX (__MCD_TOTAL_CLIP_PLANES + __MCD_MAX_POLYGON_CLIP_SIZE)
void FASTCALL __MCDDoClippedPolygon(DEVRC *pRc, MCDVERTEX **iv, ULONG nout,
ULONG allClipCodes)
{
MCDVERTEX *ov[__MCD_TOTAL_CLIP_PLANES][__MCD_MAX_CLIP_VERTEX];
MCDVERTEX **ivp;
MCDVERTEX **ovp;
MCDVERTEX *p0, *p1, *p2;
MCDCOORD *plane;
LONG i;
MCDFLOAT one;
VOID (FASTCALL *rt)(DEVRC*, MCDVERTEX*, MCDVERTEX*, MCDVERTEX*);
MCDFLOAT llx, lly, urx, ury;
MCDFLOAT winx, winy;
ULONG clipCodes;
/*
** Reset nextClipTemp pointer for any new verticies that are generated
** during the clipping.
*/
pRc->pNextClipTemp = &pRc->clipTemp[0];
ivp = &iv[0];
/*
** Check each of the clipping planes by examining the allClipCodes
** mask. Note that no bits will be set in allClipCodes for clip
** planes that are not enabled.
*/
if (allClipCodes) {
/* Now clip against the clipping planes */
ovp = &ov[0][0];
/*
** 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) & __MCD_USER_CLIP_MASK;
if (clipCodes) {
plane = &pRc->MCDState.userClipPlanes[0];
do {
if (clipCodes & 1) {
nout = clipToPlaneEye(pRc, ivp, nout, ovp, plane);
if (nout < 3) {
return;
}
ivp = ovp;
ovp += __MCD_MAX_CLIP_VERTEX;
}
clipCodes >>= 1;
plane++;
} while (clipCodes);
}
allClipCodes &= MCD_CLIP_MASK;
if (allClipCodes) {
plane = &__MCD_frustumClipPlanes[0];
do {
if (allClipCodes & 1) {
nout = clipToPlane(pRc, ivp, nout, ovp, plane);
if (nout < 3) {
return;
}
ivp = ovp;
ovp += __MCD_MAX_CLIP_VERTEX;
}
allClipCodes >>= 1;
plane++;
} while (allClipCodes);
}
/*
** Calculate final screen coordinates. Next phase of polygon
** processing assumes that window coordinates are already computed.
*/
ovp = ivp;
one = __MCDONE;
llx = pRc->MCDViewport.xCenter - pRc->MCDViewport.xScale;
urx = pRc->MCDViewport.xCenter + pRc->MCDViewport.xScale;
if (pRc->MCDViewport.yScale > 0) {
lly = pRc->MCDViewport.yCenter - pRc->MCDViewport.yScale;
ury = pRc->MCDViewport.yCenter + pRc->MCDViewport.yScale;
} else {
lly = pRc->MCDViewport.yCenter + pRc->MCDViewport.yScale;
ury = pRc->MCDViewport.yCenter - pRc->MCDViewport.yScale;
}
for (i = nout; --i >= 0; ) {
MCDFLOAT wInv;
p0 = *ovp++;
if (p0->clipCoord.w == (MCDFLOAT) 0.0)
wInv = (MCDFLOAT) 0.0;
else
wInv = one / p0->clipCoord.w;
winx = p0->clipCoord.x * pRc->MCDViewport.xScale * wInv +
pRc->MCDViewport.xCenter;
winy = p0->clipCoord.y * pRc->MCDViewport.yScale * wInv +
pRc->MCDViewport.yCenter;
/*
** Check if these window coordinates are legal. At this
** point, it is quite possible that they are not. Trivially
** pull them into the legal viewport region if necessary.
*/
if (winx < llx) winx = llx;
else if (winx > urx) winx = urx;
if (winy < lly) winy = lly;
else if (winy > ury) winy = ury;
p0->windowCoord.x = winx;
p0->windowCoord.y = winy;
p0->windowCoord.z = p0->clipCoord.z * pRc->MCDViewport.zScale * wInv +
pRc->MCDViewport.zCenter;
p0->windowCoord.w = wInv;
}
}
/*
** Subdivide the clipped polygon into triangles. Only convex polys
** are supported so this is okay to do. Non-convex polys will do
** something odd here, but thats the clients fault.
*/
p0 = *ivp++;
p1 = *ivp++;
p2 = *ivp++;
rt = pRc->renderTri;
if (nout == 3) {
(*rt)(pRc, p0, p1, p2);
} else {
for (i = 0; i < (LONG)nout - 2; i++) {
ULONG t1, t2;
if (i == 0) {
/*
** Third edge of first sub-triangle is always non-boundary
*/
t1 = p2->flags & MCDVERTEX_EDGEFLAG;
p2->flags &= ~MCDVERTEX_EDGEFLAG;
(*rt)(pRc, p0, p1, p2);
p2->flags |= t1;
} else
if (i == (LONG)nout - 3) {
/*
** First edge of last sub-triangle is always non-boundary
*/
t1 = p0->flags & MCDVERTEX_EDGEFLAG;
p0->flags &= ~MCDVERTEX_EDGEFLAG;
(*rt)(pRc, p0, p1, p2);
p0->flags |= t1;
} else {
/*
** Interior sub-triangles have the first and last edge
** marked non-boundary
*/
t1 = p0->flags & MCDVERTEX_EDGEFLAG;
t2 = p2->flags & MCDVERTEX_EDGEFLAG;
p0->flags &= ~MCDVERTEX_EDGEFLAG;
p2->flags &= ~MCDVERTEX_EDGEFLAG;
(*rt)(pRc, p0, p1, p2);
p0->flags |= t1;
p2->flags |= t2;
}
p1 = p2;
p2 = (MCDVERTEX *) *ivp++;
}
}
}
VOID FASTCALL __MCDClipPolygon(DEVRC *pRc, MCDVERTEX *v0, ULONG nv)
{
MCDVERTEX *iv[__MCD_MAX_POLYGON_CLIP_SIZE];
MCDVERTEX **ivp;
LONG i;
ULONG andCodes, orCodes;
pRc->pvProvoking = v0;
/*
** Generate array of addresses of the verticies. And all the
** clip codes together while we are at it.
*/
ivp = &iv[0];
andCodes = 0;
orCodes = 0;
for (i = nv; --i >= 0; ) {
andCodes &= v0->clipCode;
orCodes |= v0->clipCode;
*ivp++ = v0++;
}
if (andCodes != 0) {
/*
** Trivially reject the polygon. If andCodes is non-zero then
** every vertex in the polygon is outside of the same set of
** clipping planes (at least one).
*/
return;
}
__MCDDoClippedPolygon(pRc, &iv[0], nv, orCodes);
}
void FASTCALL __MCDClipTriangle(DEVRC *pRc, MCDVERTEX *a, MCDVERTEX *b,
MCDVERTEX *c, ULONG orCodes)
{
MCDVERTEX *iv[3];
iv[0] = a;
iv[1] = b;
iv[2] = c;
__MCDDoClippedPolygon(pRc, &iv[0], 3, orCodes);
}
////////////////////////////////////////////////////////////////////////
// Line clipping:
////////////////////////////////////////////////////////////////////////
//
// 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.
//
VOID FASTCALL __MCDClipLine(DEVRC *pRc, MCDVERTEX *a, MCDVERTEX *b,
BOOL bResetLine)
{
MCDVERTEX *provokingA = a;
MCDVERTEX *provokingB = b;
MCDVERTEX np1, np2;
MCDCOORD *plane;
ULONG needs, allClipCodes, clipCodes;
VOID (FASTCALL *clip)(MCDVERTEX*, const MCDVERTEX*, const MCDVERTEX*, MCDFLOAT);
MCDFLOAT zero;
MCDFLOAT winx, winy;
MCDFLOAT vpXCenter, vpYCenter, vpZCenter;
MCDFLOAT vpXScale, vpYScale, vpZScale;
MCDVIEWPORT *vp;
MCDFLOAT x, y, z, wInv;
allClipCodes = a->clipCode | b->clipCode;
/*
** For each clipping 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 = __MCDZERO;
clip = pRc->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) & __MCD_USER_CLIP_MASK;
if (clipCodes) {
plane = &pRc->MCDState.userClipPlanes[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) {
MCDFLOAT t, d1, d2;
d1 = (plane->x * a->eyeCoord.x) +
(plane->y * a->eyeCoord.y) +
(plane->z * a->eyeCoord.z) +
(plane->w * a->eyeCoord.w);
d2 = (plane->x * b->eyeCoord.x) +
(plane->y * b->eyeCoord.y) +
(plane->z * b->eyeCoord.z) +
(plane->w * b->eyeCoord.w);
if (d1 < zero) {
/* a is out */
if (d2 < zero) {
/* a & b are out */
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);
(&np1)->eyeCoord.x =
t*(a->eyeCoord.x - b->eyeCoord.x) + b->eyeCoord.x;
(&np1)->eyeCoord.y =
t*(a->eyeCoord.y - b->eyeCoord.y) + b->eyeCoord.y;
(&np1)->eyeCoord.z =
t*(a->eyeCoord.z - b->eyeCoord.z) + b->eyeCoord.z;
(&np1)->eyeCoord.w =
t*(a->eyeCoord.w - b->eyeCoord.w) + b->eyeCoord.w;
a = &np1;
a->flags = b->flags;
if (pRc->MCDState.shadeModel == GL_FLAT)
{
COPY_COLOR(a->colors[0], provokingA->colors[0]);
}
} else {
/* a is in */
if (d2 < zero) {
/*
** 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);
(&np2)->eyeCoord.x =
t*(b->eyeCoord.x - a->eyeCoord.x) + a->eyeCoord.x;
(&np2)->eyeCoord.y =
t*(b->eyeCoord.y - a->eyeCoord.y) + a->eyeCoord.y;
(&np2)->eyeCoord.z =
t*(b->eyeCoord.z - a->eyeCoord.z) + a->eyeCoord.z;
(&np2)->eyeCoord.w =
t*(b->eyeCoord.w - a->eyeCoord.w) + a->eyeCoord.w;
b = &np2;
b->flags = a->flags;
if (pRc->MCDState.shadeModel == GL_FLAT)
{
COPY_COLOR(b->colors[0], provokingB->colors[0]);
}
} else {
/* A and B are in */
}
}
}
plane++;
clipCodes >>= 1;
} while (clipCodes);
}
allClipCodes &= MCD_CLIP_MASK;
if (allClipCodes) {
plane = &__MCD_frustumClipPlanes[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) {
MCDFLOAT t, d1, d2;
d1 = (plane->x * a->clipCoord.x) + (plane->y * a->clipCoord.y) +
(plane->z * a->clipCoord.z) + (plane->w * a->clipCoord.w);
d2 = (plane->x * b->clipCoord.x) + (plane->y * b->clipCoord.y) +
(plane->z * b->clipCoord.z) + (plane->w * b->clipCoord.w);
if (d1 < zero) {
/* a is out */
if (d2 < zero) {
/* a & b are out */
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->flags = b->flags;
if (pRc->MCDState.shadeModel == GL_FLAT)
{
COPY_COLOR(a->colors[0], provokingA->colors[0]);
}
} else {
/* a is in */
if (d2 < zero) {
/*
** 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->flags = a->flags;
if (pRc->MCDState.shadeModel == GL_FLAT)
{
COPY_COLOR(b->colors[0], provokingB->colors[0]);
}
} else {
/* A and B are in */
}
}
}
plane++;
allClipCodes >>= 1;
} while (allClipCodes);
}
vp = &pRc->MCDViewport;
vpXCenter = vp->xCenter;
vpYCenter = vp->yCenter;
vpZCenter = vp->zCenter;
vpXScale = vp->xScale;
vpYScale = vp->yScale;
vpZScale = vp->zScale;
/* Compute window coordinates for both vertices. */
wInv = __MCDONE / a->clipCoord.w;
x = a->clipCoord.x;
y = a->clipCoord.y;
z = a->clipCoord.z;
winx = x * vpXScale * wInv + vpXCenter;
winy = y * vpYScale * wInv + vpYCenter;
a->windowCoord.z = z * vpZScale * wInv + vpZCenter;
a->windowCoord.w = wInv;
a->windowCoord.x = winx;
a->windowCoord.y = winy;
wInv = __MCDONE / b->clipCoord.w;
x = b->clipCoord.x;
y = b->clipCoord.y;
z = b->clipCoord.z;
winx = x * vpXScale * wInv + vpXCenter;
winy = y * vpYScale * wInv + vpYCenter;
b->windowCoord.z = z * vpZScale * wInv + vpZCenter;
b->windowCoord.w = wInv;
b->windowCoord.x = winx;
b->windowCoord.y = winy;
/* Validate line state */
if (pRc->MCDState.shadeModel == 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
bResetLine = TRUE;
}
// 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
(*pRc->renderLine)(pRc, a, b, bResetLine);
} else {
if (provokingA->clipCode != 0)
{
bResetLine = TRUE;
}
(*pRc->renderLine)(pRc, a, b, bResetLine);
}
}