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/* $Id: clip.c,v 1.7 1996/10/29 02:55:02 brianp Exp $ */ /* * Mesa 3-D graphics library * Version: 2.0 * Copyright (C) 1995-1996 Brian Paul * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this library; if not, write to the Free * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* * $Log: clip.c,v $ * Revision 1.7 1996/10/29 02:55:02 brianp * fixed duplicate vertex bug in gl_viewclip_polygon() * * Revision 1.6 1996/10/07 23:48:33 brianp * changed temporaries to GLdouble in gl_viewclip_polygon() * * Revision 1.5 1996/10/03 01:43:45 brianp * changed INSIDE() macro in gl_viewclip_polygon() to work like other macros * * Revision 1.4 1996/10/03 01:36:33 brianp * changed COMPUTE_INTERSECTION macros in gl_viewclip_polygon to avoid * potential roundoff errors * * Revision 1.3 1996/09/27 01:24:23 brianp * removed unused variables * * Revision 1.2 1996/09/15 01:48:58 brianp * removed #define NULL 0 * * Revision 1.1 1996/09/13 01:38:16 brianp * Initial revision * */ #include <string.h> #include "clip.h" #include "context.h" #include "dlist.h" #include "macros.h" #include "matrix.h" #include "types.h" #include "vb.h" #include "xform.h" /* Linear interpolation between A and B: */ #define LINTERP( T, A, B ) ( (A) + (T) * ( (B) - (A) ) ) #define EYE_SPACE 1 #define CLIP_SPACE 2 static GLuint Space; /* * This function is used to interpolate colors, indexes, and texture * coordinates when clipping has to be done. In general, we compute * aux[dst] = aux[in] + t * (aux[out] - aux[in]) * where aux is the quantity to be interpolated. * Input: dst - index of array position to store interpolated value * t - a value in [0,1] * in - index of array position corresponding to 'inside' vertex * out - index of array position corresponding to 'outside' vertex */ static void interpolate_aux( GLcontext* ctx, GLuint dst, GLfloat t, GLuint in, GLuint out ) { struct vertex_buffer* VB = ctx->VB; if (ctx->ClipMask & CLIP_FCOLOR_BIT) { VB->Fcolor[dst][0] = LINTERP( t, VB->Fcolor[in][0], VB->Fcolor[out][0] ); VB->Fcolor[dst][1] = LINTERP( t, VB->Fcolor[in][1], VB->Fcolor[out][1] ); VB->Fcolor[dst][2] = LINTERP( t, VB->Fcolor[in][2], VB->Fcolor[out][2] ); VB->Fcolor[dst][3] = LINTERP( t, VB->Fcolor[in][3], VB->Fcolor[out][3] ); } else if (ctx->ClipMask & CLIP_FINDEX_BIT) { VB->Findex[dst] = (GLuint) (GLint) LINTERP( t, (GLfloat) VB->Findex[in], (GLfloat) VB->Findex[out] ); } if (ctx->ClipMask & CLIP_BCOLOR_BIT) { VB->Bcolor[dst][0] = LINTERP( t, VB->Bcolor[in][0], VB->Bcolor[out][0] ); VB->Bcolor[dst][1] = LINTERP( t, VB->Bcolor[in][1], VB->Bcolor[out][1] ); VB->Bcolor[dst][2] = LINTERP( t, VB->Bcolor[in][2], VB->Bcolor[out][2] ); VB->Bcolor[dst][3] = LINTERP( t, VB->Bcolor[in][3], VB->Bcolor[out][3] ); } else if (ctx->ClipMask & CLIP_BINDEX_BIT) { VB->Bindex[dst] = (GLuint) (GLint) LINTERP( t, (GLfloat) VB->Bindex[in], (GLfloat) VB->Bindex[out] ); } if (ctx->ClipMask & CLIP_TEXTURE_BIT) { /* TODO: is more sophisticated texture coord interpolation needed?? */ if (Space==CLIP_SPACE) { /* also interpolate eye Z component */ VB->Eye[dst][2] = LINTERP( t, VB->Eye[in][2], VB->Eye[out][2] ); } VB->TexCoord[dst][0] = LINTERP(t,VB->TexCoord[in][0],VB->TexCoord[out][0]); VB->TexCoord[dst][1] = LINTERP(t,VB->TexCoord[in][1],VB->TexCoord[out][1]); VB->TexCoord[dst][2] = LINTERP(t,VB->TexCoord[in][2],VB->TexCoord[out][2]); VB->TexCoord[dst][3] = LINTERP(t,VB->TexCoord[in][3],VB->TexCoord[out][3]); } } void gl_ClipPlane( GLcontext* ctx, GLenum plane, const GLfloat *equation ) { GLint p; p = (GLint) (plane - GL_CLIP_PLANE0); if (p<0 || p>=MAX_CLIP_PLANES) { gl_error( ctx, GL_INVALID_ENUM, "glClipPlane" ); return; } /* * The Equation is transformed by the transpose of the inverse of the * current modelview matrix and stored in the resulting eye coordinates. */ if (!ctx->ModelViewInvValid) { gl_compute_modelview_inverse(ctx); } gl_transform_vector( ctx->Transform.ClipEquation[p], equation, ctx->ModelViewInv ); } void gl_GetClipPlane( GLcontext* ctx, GLenum plane, GLdouble *equation ) { GLint p; if (INSIDE_BEGIN_END(ctx)) { gl_error( ctx, GL_INVALID_OPERATION, "glGetClipPlane" ); return; } p = (GLint) (plane - GL_CLIP_PLANE0); if (p<0 || p>=MAX_CLIP_PLANES) { gl_error( ctx, GL_INVALID_ENUM, "glGetClipPlane" ); return; } equation[0] = (GLdouble) ctx->Transform.ClipEquation[p][0]; equation[1] = (GLdouble) ctx->Transform.ClipEquation[p][1]; equation[2] = (GLdouble) ctx->Transform.ClipEquation[p][2]; equation[3] = (GLdouble) ctx->Transform.ClipEquation[p][3]; } /**********************************************************************/ /* View volume clipping. */ /**********************************************************************/ /* * Clip a point against the view volume. * Input: v - vertex-vector describing the point to clip * Return: 0 = outside view volume * 1 = inside view volume */ GLuint gl_viewclip_point( const GLfloat v[] ) { if ( v[0] > v[3] || v[0] < -v[3] || v[1] > v[3] || v[1] < -v[3] || v[2] > v[3] || v[2] < -v[3] ) { return 0; } else { return 1; } } /* * Clip a line segment against the view volume defined by -w<=x,y,z<=w. * Input: i, j - indexes into VB->V* of endpoints of the line * Return: 0 = line completely outside of view * 1 = line is inside view. */ GLuint gl_viewclip_line( GLcontext* ctx, GLuint *i, GLuint *j ) { struct vertex_buffer* VB = ctx->VB; GLfloat t, dx, dy, dz, dw; register GLuint ii, jj; Space = CLIP_SPACE; ii = *i; jj = *j; /* * We use 6 instances of this code to clip agains the 6 planes. * For each plane, we define the OUTSIDE and COMPUTE_INTERSECTION * macros apprpriately. */ #define GENERAL_CLIP \ if (OUTSIDE(ii)) { \ if (OUTSIDE(jj)) { \ /* both verts are outside ==> return 0 */ \ return 0; \ } \ else { \ /* ii is outside, jj is inside ==> clip */ \ /* new vertex put in position VB->Free */ \ COMPUTE_INTERSECTION( VB->Free, jj, ii ) \ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, t, jj, ii );\ ii = VB->Free; \ VB->Free++; \ if (VB->Free==VB_SIZE) VB->Free = 1; \ } \ } \ else { \ if (OUTSIDE(jj)) { \ /* ii is inside, jj is outside ==> clip */ \ /* new vertex put in position VB->Free */ \ COMPUTE_INTERSECTION( VB->Free, ii, jj ); \ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, t, ii, jj );\ jj = VB->Free; \ VB->Free++; \ if (VB->Free==VB_SIZE) VB->Free = 1; \ } \ /* else both verts are inside ==> do nothing */ \ } #define X(I) VB->Clip[I][0] #define Y(I) VB->Clip[I][1] #define Z(I) VB->Clip[I][2] #define W(I) VB->Clip[I][3] /* * Begin clipping */ /*** Clip against +X side ***/ #define OUTSIDE(K) (X(K) > W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dx = X(out) - X(in); \ dw = W(out) - W(in); \ t = (X(in) - W(in)) / (dw-dx); \ X(new) = X(in) + t * dx; \ Y(new) = Y(in) + t * (Y(out) - Y(in)); \ Z(new) = Z(in) + t * (Z(out) - Z(in)); \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION /*** Clip against -X side ***/ #define OUTSIDE(K) (X(K) < -W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dx = X(out) - X(in); \ dw = W(out) - W(in); \ t = -(X(in) + W(in)) / (dw+dx); \ X(new) = X(in) + t * dx; \ Y(new) = Y(in) + t * (Y(out) - Y(in)); \ Z(new) = Z(in) + t * (Z(out) - Z(in)); \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION /*** Clip against +Y side ***/ #define OUTSIDE(K) (Y(K) > W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dy = Y(out) - Y(in); \ dw = W(out) - W(in); \ t = (Y(in) - W(in)) / (dw-dy); \ X(new) = X(in) + t * (X(out) - X(in)); \ Y(new) = Y(in) + t * dy; \ Z(new) = Z(in) + t * (Z(out) - Z(in)); \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION /*** Clip against -Y side ***/ #define OUTSIDE(K) (Y(K) < -W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dy = Y(out) - Y(in); \ dw = W(out) - W(in); \ t = -(Y(in) + W(in)) / (dw+dy); \ X(new) = X(in) + t * (X(out) - X(in)); \ Y(new) = Y(in) + t * dy; \ Z(new) = Z(in) + t * (Z(out) - Z(in)); \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION /*** Clip against +Z side ***/ #define OUTSIDE(K) (Z(K) > W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dz = Z(out) - Z(in); \ dw = W(out) - W(in); \ t = (Z(in) - W(in)) / (dw-dz); \ X(new) = X(in) + t * (X(out) - X(in)); \ Y(new) = Y(in) + t * (Y(out) - Y(in)); \ Z(new) = Z(in) + t * dz; \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION /*** Clip against -Z side ***/ #define OUTSIDE(K) (Z(K) < -W(K)) #define COMPUTE_INTERSECTION( new, in, out ) \ dz = Z(out) - Z(in); \ dw = W(out) - W(in); \ t = -(Z(in) + W(in)) / (dw+dz); \ X(new) = X(in) + t * (X(out) - X(in)); \ Y(new) = Y(in) + t * (Y(out) - Y(in)); \ Z(new) = Z(in) + t * dz; \ W(new) = W(in) + t * dw; GENERAL_CLIP #undef OUTSIDE #undef COMPUTE_INTERSECTION #undef GENERAL_CLIP *i = ii; *j = jj; return 1; } /* * Clip a polygon against the view volume defined by -w<=x,y,z<=w. * Input: n - number of vertices in input polygon. * vlist - list of indexes into VB->V* of polygon to clip. * Output: vlist - modified list of vertex indexes * Return: number of vertices in resulting polygon */ GLuint gl_viewclip_polygon( GLcontext* ctx, GLuint n, GLuint vlist[] ) { struct vertex_buffer* VB = ctx->VB; GLuint previ, prevj; GLuint curri, currj; GLuint vlist2[VB_MAX]; GLuint n2; GLdouble dx, dy, dz, dw, t, neww; Space = CLIP_SPACE; /* * We use 6 instances of this code to implement clipping against the * 6 sides of the view volume. Prior to each we define the macros: * INLIST = array which lists input vertices * OUTLIST = array which lists output vertices * INCOUNT = variable which is the number of vertices in INLIST[] * OUTCOUNT = variable which is the number of vertices in OUTLIST[] * INSIDE(v) = test if vertex v[] is inside the view volume * COMPUTE_INTERSECTION(inv,outv,newv) = compute intersection of line * from inv[] to outv[] with the clipping plane and store * the result in newv[] */ #define GENERAL_CLIP \ if (INCOUNT<3) return 0; \ previ = INCOUNT-1; /* let previous = last vertex */ \ prevj = INLIST[previ]; \ OUTCOUNT = 0; \ for (curri=0;curri<INCOUNT;curri++) { \ currj = INLIST[curri]; \ if (INSIDE(VB->Clip[currj])) { \ if (INSIDE(VB->Clip[prevj])) { \ /* both verts are inside ==> copy current to outlist */ \ OUTLIST[OUTCOUNT] = currj; \ OUTCOUNT++; \ } \ else { \ /* current is inside and previous is outside ==> clip */ \ COMPUTE_INTERSECTION( VB->Clip[currj], VB->Clip[prevj], \ VB->Clip[VB->Free] ) \ /* if new point not coincident with previous point... */ \ if (t>0.0) { \ /* interpolate aux info using the value of t */ \ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, \ t, currj, prevj ); \ VB->Edgeflag[VB->Free] = VB->Edgeflag[prevj]; \ /* output new point */ \ OUTLIST[OUTCOUNT] = VB->Free; \ VB->Free++; \ if (VB->Free==VB_SIZE) VB->Free = 1; \ OUTCOUNT++; \ } \ /* Output current */ \ OUTLIST[OUTCOUNT] = currj; \ OUTCOUNT++; \ } \ } \ else { \ if (INSIDE(VB->Clip[prevj])) { \ /* current is outside and previous is inside ==> clip */ \ COMPUTE_INTERSECTION( VB->Clip[prevj], VB->Clip[currj], \ VB->Clip[VB->Free] ) \ /* if new point not coincident with previous point... */ \ if (t>0.0) { \ /* interpolate aux info using the value of t */ \ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, \ t, prevj, currj ); \ VB->Edgeflag[VB->Free] = VB->Edgeflag[prevj]; \ /* output new point */ \ OUTLIST[OUTCOUNT] = VB->Free; \ VB->Free++; \ if (VB->Free==VB_SIZE) VB->Free = 1; \ OUTCOUNT++; \ } \ } \ /* else both verts are outside ==> do nothing */ \ } \ /* let previous = current */ \ previ = curri; \ prevj = currj; \ } /* * Clip against +X */ #define INCOUNT n #define OUTCOUNT n2 #define INLIST vlist #define OUTLIST vlist2 #define INSIDE(v) ( v[0] <= v[3] ) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dx = outv[0] - inv[0]; \ dw = outv[3] - inv[3]; \ t = (inv[0]-inv[3]) / (dw-dx); \ neww = inv[3] + t * dw; \ newv[0] = neww; \ newv[1] = inv[1] + t * (outv[1]-inv[1]); \ newv[2] = inv[2] + t * (outv[2]-inv[2]); \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef OUTCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* * Clip against -X */ #define INCOUNT n2 #define OUTCOUNT n #define INLIST vlist2 #define OUTLIST vlist #define INSIDE(v) (v[0] >= -v[3]) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dx = outv[0]-inv[0]; \ dw = outv[3]-inv[3]; \ t = -(inv[0]+inv[3]) / (dw+dx); \ neww = inv[3] + t * dw; \ newv[0] = -neww; \ newv[1] = inv[1] + t * (outv[1]-inv[1]); \ newv[2] = inv[2] + t * (outv[2]-inv[2]); \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef OUTCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* * Clip against +Y */ #define INCOUNT n #define OUTCOUNT n2 #define INLIST vlist #define OUTLIST vlist2 #define INSIDE(v) (v[1] <= v[3]) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dy = outv[1]-inv[1]; \ dw = outv[3]-inv[3]; \ t = (inv[1]-inv[3]) / (dw-dy); \ neww = inv[3] + t * dw; \ newv[0] = inv[0] + t * (outv[0]-inv[0]); \ newv[1] = neww; \ newv[2] = inv[2] + t * (outv[2]-inv[2]); \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef OUTCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* * Clip against -Y */ #define INCOUNT n2 #define OUTCOUNT n #define INLIST vlist2 #define OUTLIST vlist #define INSIDE(v) (v[1] >= -v[3]) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dy = outv[1]-inv[1]; \ dw = outv[3]-inv[3]; \ t = -(inv[1]+inv[3]) / (dw+dy); \ neww = inv[3] + t * dw; \ newv[0] = inv[0] + t * (outv[0]-inv[0]); \ newv[1] = -neww; \ newv[2] = inv[2] + t * (outv[2]-inv[2]); \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef OUTCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* * Clip against +Z */ #define INCOUNT n #define OUTCOUNT n2 #define INLIST vlist #define OUTLIST vlist2 #define INSIDE(v) (v[2] <= v[3]) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dz = outv[2]-inv[2]; \ dw = outv[3]-inv[3]; \ t = (inv[2]-inv[3]) / (dw-dz); \ neww = inv[3] + t * dw; \ newv[0] = inv[0] + t * (outv[0]-inv[0]); \ newv[1] = inv[1] + t * (outv[1]-inv[1]); \ newv[2] = neww; \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef OUTCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* * Clip against -Z */ #define INCOUNT n2 #define OUTCOUNT n #define INLIST vlist2 #define OUTLIST vlist #define INSIDE(v) (v[2] >= -v[3]) #define COMPUTE_INTERSECTION( inv, outv, newv ) \ dz = outv[2]-inv[2]; \ dw = outv[3]-inv[3]; \ t = -(inv[2]+inv[3]) / (dw+dz); \ neww = inv[3] + t * dw; \ newv[0] = inv[0] + t * (outv[0]-inv[0]); \ newv[1] = inv[1] + t * (outv[1]-inv[1]); \ newv[2] = -neww; \ newv[3] = neww; GENERAL_CLIP #undef INCOUNT #undef INLIST #undef OUTLIST #undef INSIDE #undef COMPUTE_INTERSECTION /* 'OUTCOUNT' clipped vertices are now back in v[] */ return OUTCOUNT; #undef GENERAL_CLIP #undef OUTCOUNT } /**********************************************************************/ /* Clipping against user-defined clipping planes. */ /**********************************************************************/ /* * If the dot product of the eye coordinates of a vertex with the * stored plane equation components is positive or zero, the vertex * is in with respect to that clipping plane, otherwise it is out. */ /* * Clip a point against the user clipping planes. * Input: v - vertex-vector describing the point to clip. * Return: 0 = point was clipped * 1 = point not clipped */ GLuint gl_userclip_point( GLcontext* ctx, const GLfloat v[] ) { GLuint p; for (p=0;p<MAX_CLIP_PLANES;p++) { if (ctx->Transform.ClipEnabled[p]) { GLfloat dot = v[0] * ctx->Transform.ClipEquation[p][0] + v[1] * ctx->Transform.ClipEquation[p][1] + v[2] * ctx->Transform.ClipEquation[p][2] + v[3] * ctx->Transform.ClipEquation[p][3]; if (dot < 0.0F) { return 0; } } } return 1; } #define MAGIC_NUMBER -0.8e-03F /* Test if VB->Eye[J] is inside the clipping plane defined by A,B,C,D */ #define INSIDE( J, A, B, C, D ) \ ( (VB->Eye[J][0] * A + VB->Eye[J][1] * B \ + VB->Eye[J][2] * C + VB->Eye[J][3] * D) >= MAGIC_NUMBER ) /* Test if VB->Eye[J] is outside the clipping plane defined by A,B,C,D */ #define OUTSIDE( J, A, B, C, D ) \ ( (VB->Eye[J][0] * A + VB->Eye[J][1] * B \ + VB->Eye[J][2] * C + VB->Eye[J][3] * D) < MAGIC_NUMBER ) /* * Clip a line against the user clipping planes. * Input: i, j - indexes into VB->V*[] of endpoints * Output: i, j - indexes into VB->V*[] of (possibly clipped) endpoints * Return: 0 = line completely clipped * 1 = line is visible */ GLuint gl_userclip_line( GLcontext* ctx, GLuint *i, GLuint *j ) { struct vertex_buffer* VB = ctx->VB; GLuint p, ii, jj; Space = EYE_SPACE; ii = *i; jj = *j; for (p=0;p<MAX_CLIP_PLANES;p++) { if (ctx->Transform.ClipEnabled[p]) { register GLfloat a, b, c, d; a = ctx->Transform.ClipEquation[p][0]; b = ctx->Transform.ClipEquation[p][1]; c = ctx->Transform.ClipEquation[p][2]; d = ctx->Transform.ClipEquation[p][3]; if (OUTSIDE( ii, a,b,c,d )) { if (OUTSIDE( jj, a,b,c,d )) { /* ii and jj outside ==> quit */ return 0; } else { /* ii is outside, jj is inside ==> clip */ GLfloat dx, dy, dz, dw, t, denom; dx = VB->Eye[ii][0] - VB->Eye[jj][0]; dy = VB->Eye[ii][1] - VB->Eye[jj][1]; dz = VB->Eye[ii][2] - VB->Eye[jj][2]; dw = VB->Eye[ii][3] - VB->Eye[jj][3]; denom = dx*a + dy*b + dz*c + dw*d; if (denom==0.0) { t = 0.0; } else { t = -(VB->Eye[jj][0]*a+VB->Eye[jj][1]*b +VB->Eye[jj][2]*c+VB->Eye[jj][3]*d) / denom; if (t>1.0F) t = 1.0F; } VB->Eye[VB->Free][0] = VB->Eye[jj][0] + t * dx; VB->Eye[VB->Free][1] = VB->Eye[jj][1] + t * dy; VB->Eye[VB->Free][2] = VB->Eye[jj][2] + t * dz; VB->Eye[VB->Free][3] = VB->Eye[jj][3] + t * dw; /* Interpolate colors, indexes, and/or texture coords */ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, t, jj, ii ); ii = VB->Free; VB->Free++; if (VB->Free==VB_SIZE) VB->Free = 1; } } else { if (OUTSIDE( jj, a,b,c,d )) { /* ii is inside, jj is outside ==> clip */ GLfloat dx, dy, dz, dw, t, denom; dx = VB->Eye[jj][0] - VB->Eye[ii][0]; dy = VB->Eye[jj][1] - VB->Eye[ii][1]; dz = VB->Eye[jj][2] - VB->Eye[ii][2]; dw = VB->Eye[jj][3] - VB->Eye[ii][3]; denom = dx*a + dy*b + dz*c + dw*d; if (denom==0.0) { t = 0.0; } else { t = -(VB->Eye[ii][0]*a+VB->Eye[ii][1]*b +VB->Eye[ii][2]*c+VB->Eye[ii][3]*d) / denom; if (t>1.0F) t = 1.0F; } VB->Eye[VB->Free][0] = VB->Eye[ii][0] + t * dx; VB->Eye[VB->Free][1] = VB->Eye[ii][1] + t * dy; VB->Eye[VB->Free][2] = VB->Eye[ii][2] + t * dz; VB->Eye[VB->Free][3] = VB->Eye[ii][3] + t * dw; /* Interpolate colors, indexes, and/or texture coords */ if (ctx->ClipMask) interpolate_aux( ctx, VB->Free, t, ii, jj ); jj = VB->Free; VB->Free++; if (VB->Free==VB_SIZE) VB->Free = 1; } else { /* ii and jj inside ==> do nothing */ } } } } *i = ii; *j = jj; return 1; } /* * Clip a polygon against the user clipping planes defined in eye coordinates. * Input: n - number of vertices. * vlist - list of vertices in input polygon. * Output: vlist - list of vertices in output polygon. * Return: number of vertices after clipping. */ GLuint gl_userclip_polygon( GLcontext* ctx, GLuint n, GLuint vlist[] ) { struct vertex_buffer* VB = ctx->VB; GLuint vlist2[VB_MAX]; GLuint *inlist, *outlist; GLuint incount, outcount; GLuint curri, currj; GLuint previ, prevj; GLuint p; Space = EYE_SPACE; /* initialize input vertex list */ incount = n; inlist = vlist; outlist = vlist2; for (p=0;p<MAX_CLIP_PLANES;p++) { if (ctx->Transform.ClipEnabled[p]) { register float a = ctx->Transform.ClipEquation[p][0]; register float b = ctx->Transform.ClipEquation[p][1]; register float c = ctx->Transform.ClipEquation[p][2]; register float d = ctx->Transform.ClipEquation[p][3]; if (incount<3) return 0; /* initialize prev to be last in the input list */ previ = incount - 1; prevj = inlist[previ]; outcount = 0; for (curri=0;curri<incount;curri++) { currj = inlist[curri]; if (INSIDE(currj, a,b,c,d)) { if (INSIDE(prevj, a,b,c,d)) { /* both verts are inside ==> copy current to outlist */ outlist[outcount++] = currj; } else { /* current is inside and previous is outside ==> clip */ GLfloat dx, dy, dz, dw, t, denom; /* compute t */ dx = VB->Eye[prevj][0] - VB->Eye[currj][0]; dy = VB->Eye[prevj][1] - VB->Eye[currj][1]; dz = VB->Eye[prevj][2] - VB->Eye[currj][2]; dw = VB->Eye[prevj][3] - VB->Eye[currj][3]; denom = dx*a + dy*b + dz*c + dw*d; if (denom==0.0) { t = 0.0; } else { t = -(VB->Eye[currj][0]*a+VB->Eye[currj][1]*b +VB->Eye[currj][2]*c+VB->Eye[currj][3]*d) / denom; if (t>1.0F) { t = 1.0F; } } /* interpolate new vertex position */ VB->Eye[VB->Free][0] = VB->Eye[currj][0] + t*dx; VB->Eye[VB->Free][1] = VB->Eye[currj][1] + t*dy; VB->Eye[VB->Free][2] = VB->Eye[currj][2] + t*dz; VB->Eye[VB->Free][3] = VB->Eye[currj][3] + t*dw; /* interpolate color, index, and/or texture coord */ if (ctx->ClipMask) { interpolate_aux( ctx, VB->Free, t, currj, prevj); } VB->Edgeflag[VB->Free] = VB->Edgeflag[prevj]; /* output new vertex */ outlist[outcount++] = VB->Free; VB->Free++; if (VB->Free==VB_SIZE) VB->Free = 1; /* output current vertex */ outlist[outcount++] = currj; } } else { if (INSIDE(prevj, a,b,c,d)) { /* current is outside and previous is inside ==> clip */ GLfloat dx, dy, dz, dw, t, denom; /* compute t */ dx = VB->Eye[currj][0]-VB->Eye[prevj][0]; dy = VB->Eye[currj][1]-VB->Eye[prevj][1]; dz = VB->Eye[currj][2]-VB->Eye[prevj][2]; dw = VB->Eye[currj][3]-VB->Eye[prevj][3]; denom = dx*a + dy*b + dz*c + dw*d; if (denom==0.0) { t = 0.0; } else { t = -(VB->Eye[prevj][0]*a+VB->Eye[prevj][1]*b +VB->Eye[prevj][2]*c+VB->Eye[prevj][3]*d) / denom; if (t>1.0F) { t = 1.0F; } } /* interpolate new vertex position */ VB->Eye[VB->Free][0] = VB->Eye[prevj][0] + t*dx; VB->Eye[VB->Free][1] = VB->Eye[prevj][1] + t*dy; VB->Eye[VB->Free][2] = VB->Eye[prevj][2] + t*dz; VB->Eye[VB->Free][3] = VB->Eye[prevj][3] + t*dw; /* interpolate color, index, and/or texture coord */ if (ctx->ClipMask) { interpolate_aux( ctx, VB->Free, t, prevj, currj); } VB->Edgeflag[VB->Free] = VB->Edgeflag[prevj]; /* output new vertex */ outlist[outcount++] = VB->Free; VB->Free++; if (VB->Free==VB_SIZE) VB->Free = 1; } /* else both verts are outside ==> do nothing */ } previ = curri; prevj = currj; } /* for i */ /* swap inv and outv pointers */ { GLuint *tmp; tmp = inlist; inlist = outlist; outlist = tmp; incount = outcount; } } /* if */ } /* for p */ /* outlist points to the list of vertices resulting from the last */ /* clipping. If outlist == vlist2 then we have to copy the vertices */ /* back to vlist */ if (outlist!=vlist2) { MEMCPY( vlist, vlist2, outcount * sizeof(GLuint) ); } return outcount; }
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.