source: vbox/trunk/src/VBox/HostServices/SharedOpenGL/crserverlib/server_clip.cpp@ 78375

/* Copyright (c) 2001, Stanford University
 * All rights reserved
 *
 * See the file LICENSE.txt for information on redistributing this software.
 */

/*
 * This code contributed by Karl Rasche <[email protected]>
 */


#include <math.h>

#include "cr_server.h"
#include "cr_mem.h"
#include "server.h"


static void
__find_intersection(double *s, double *e, double *clp, double *clp_next,
                                                                                double *intr)
{
        double v1[2], v2[2];
        double A, B, T;

        v1[0] = e[0] - s[0];
        v1[1] = e[1] - s[1];
        v2[0] = clp_next[0] - clp[0];
        v2[1] = clp_next[1] - clp[1];
        
        if ((v1[1]) && (v2[0]))
        {
                A =  (clp[1]-s[1])/v1[1] + (v2[1]/v1[1])*(s[0]-clp[0])/v2[0];
                B = 1.-(v2[1]/v1[1])*(v1[0]/v2[0]);
                if (B)
                        T = A/B;
                else
                {
                        T = 0;
                }

                intr[0] = s[0]+T*v1[0];
                intr[1] = s[1]+T*v1[1];
        }
        else
        if (v1[1])
        {
                /* clp -> clp_next is vertical */
                T = (clp[0]-s[0])/v1[0];

                intr[0] = s[0]+T*v1[0];
                intr[1] = s[1]+T*v1[1];
        }
        else
        {
                /* s -> e is horizontal */
                T = (s[1]-clp[1])/v2[1];

                intr[0] = clp[0]+T*v2[0];
                intr[1] = clp[1]+T*v2[1];
        }

}

static void
 __clip_one_side(double *poly, int npnts, double *clp, double *clp_next,
                                                                 double *norm, 
                                                                 double **new_poly_in, int *new_npnts_in,
                                                                 double **new_poly_out, int *new_npnts_out)
{
        int a, sin, ein;
        double *s, *e, intr[2]; 
        
        *new_poly_in  = (double *)crAlloc(2*npnts*2*sizeof(double));
        *new_npnts_in = 0;

        *new_poly_out  = (double *)crAlloc(2*npnts*2*sizeof(double));
        *new_npnts_out = 0;

        s = poly;

        for (a=0; a<npnts; a++)
        {
                e = poly+2*((a+1)%npnts);

                if (((e[0]-clp[0])*norm[0]) + ((e[1]-clp[1])*norm[1]) >= 0)
                        ein = 0;
                else
                        ein = 1;

                if (((s[0]-clp[0])*norm[0]) + ((s[1]-clp[1])*norm[1]) >= 0)
                        sin = 0;
                else
                        sin = 1;
        
                if (sin && ein)
                {
                        /* case 1: */
                        crMemcpy(*new_poly_in+2*(*new_npnts_in), e, 2*sizeof(double));
                        (*new_npnts_in)++;
                }
                else
                if (sin && (!ein))
                {
                        /* case 2: */

                        __find_intersection(s, e, clp, clp_next, intr);

                        crMemcpy(*new_poly_in+2*(*new_npnts_in), intr, 2*sizeof(double));
                        (*new_npnts_in)++;

                        crMemcpy(*new_poly_out+2*(*new_npnts_out), intr, 2*sizeof(double));
                        (*new_npnts_out)++;
                        crMemcpy(*new_poly_out+2*(*new_npnts_out), e, 2*sizeof(double));
                        (*new_npnts_out)++;
                }
                else
                if ((!sin) && ein)
                {
                        /* case 4: */
                        __find_intersection(s, e, clp, clp_next, intr);

                        crMemcpy((*new_poly_in)+2*(*new_npnts_in), intr, 2*sizeof(double));
                        (*new_npnts_in)++;
                        crMemcpy((*new_poly_in)+2*(*new_npnts_in), e, 2*sizeof(double));
                        (*new_npnts_in)++;

                        crMemcpy(*new_poly_out+2*(*new_npnts_out), intr, 2*sizeof(double));
                        (*new_npnts_out)++;
                }
                else
                {
                        crMemcpy(*new_poly_out+2*(*new_npnts_out), e, 2*sizeof(double));
                        (*new_npnts_out)++;
                }

                s =  e;
        }
}

/* 
 * Sutherland/Hodgman clipping for interior & exterior regions. 
 * length_of((*new_vert_out)[a]) == nclip_to_vert
 */
static void
__clip(double *poly, int nvert, double *clip_to_poly, int nclip_to_vert,
                         double **new_vert_in, int *nnew_vert_in,
                         double ***new_vert_out, int **nnew_vert_out)
{
        int a, side, *nout;
        double *clip_normals, *s, *e, *n, *new_vert_src; 
        double *norm, *clp, *clp_next;
        double **out;
        
        *new_vert_out = (double **)crAlloc(nclip_to_vert*sizeof(double *));
        *nnew_vert_out = (int *)crAlloc(nclip_to_vert*sizeof(int));

        /* 
         * First, compute normals for the clip poly. This 
         * breaks for multiple (3+) adjacent colinear vertices
         */
        clip_normals = (double *)crAlloc(nclip_to_vert*2*sizeof(double));
        for (a=0; a<nclip_to_vert; a++)
        {
                s = clip_to_poly+2*a;
                e = clip_to_poly+2*((a+1)%nclip_to_vert);
                n = clip_to_poly+2*((a+2)%nclip_to_vert);

                norm = clip_normals+2*a;
                norm[0]   = e[1]-s[1];
                norm[1] = -1*(e[0]-s[0]);
                
                /* 
                 * if dot(norm, n-e) > 0), the normals are backwards,
                 *      assuming the clip region is convex 
                 */ 
                if (norm[0]*(n[0]-e[0]) + norm[1]*(n[1]-e[1]) > 0)
                {
                        norm[0] *= -1;
                        norm[1] *= -1;
                }
        }

        new_vert_src  = (double *)crAlloc(nvert*nclip_to_vert*2*sizeof(double));
        crMemcpy(new_vert_src, poly, 2*nvert*sizeof(double));

        for (side=0; side<nclip_to_vert; side++)
        {
                clp      = clip_to_poly+2*side;
                clp_next = clip_to_poly+2*((side+1)%nclip_to_vert);
                norm = clip_normals+2*side;
                *nnew_vert_in = 0;

                nout = (*nnew_vert_out)+side;
                out  = (*new_vert_out)+side;

                __clip_one_side(new_vert_src, nvert, clp, clp_next, norm,
                                new_vert_in, nnew_vert_in, 
                                out, nout);

                crMemcpy(new_vert_src, (*new_vert_in), 2*(*nnew_vert_in)*sizeof(double));
                if (side != nclip_to_vert-1)
                        crFree(*new_vert_in);
                nvert = *nnew_vert_in;
        }
}

/* 
 * Given a bitmap and a group of 'base' polygons [the quads we are testing],
 * perform the unions and differences specified by the map and return
 * the resulting geometry
 */
static void
__execute_combination(CRPoly **base, int n, int *mask, CRPoly **head)
{
        int a, b, got_intr;
        int nin, *nout, last;
        double *in, **out;
        CRPoly *intr, *diff, *p;

        *head = NULL;

        intr = (CRPoly *)crAlloc(sizeof(CRPoly));
        intr->next = NULL;

        got_intr = 0;

        /* first, intersect the first 2 polys marked */
        for (a=0; a<n; a++)
                if (mask[a]) break;
        for (b=a+1; b<n; b++)
                if (mask[b]) break;

        __clip(base[a]->points, base[a]->npoints, 
                                base[b]->points, base[b]->npoints,
                                &in, &nin, &out, &nout);
        last = b;

        crFree (nout);
        for (a=0; a<base[last]->npoints; a++)
                if (out[a])
                        crFree(out[a]);
        crFree(out);
                                        

        if (nin)
        {
                intr->npoints = nin;
                intr->points = in;
                got_intr = 1;
        }

        while (1)
        {
                for (a=last+1; a<n; a++)
                        if (mask[a]) break;

                if (a == n) break;

                if (got_intr)
                {
                        __clip(base[a]->points, base[a]->npoints, 
                                        intr->points, intr->npoints,
                                        &in, &nin, &out, &nout);

                        crFree (nout);
                        for (b=0; b<intr->npoints; b++)
                                if (out[b])
                                        crFree(out[b]);
                        crFree(out);

                        if (nin)
                        {
                                intr->npoints = nin;
                                intr->points = in;
                        }
                        else
                        {
                                got_intr = 0;
                                break;
                        }
                }
                else
                {
                        __clip(base[a]->points, base[a]->npoints, 
                                        base[last]->points, base[last]->npoints,
                                        &in, &nin, &out, &nout);
                        
                        crFree (nout);
                        for (b=0; b<base[last]->npoints; b++)
                        {
                                if (out[b])
                                        crFree(out[b]);
                        }
                        crFree(out);


                        if (nin)
                        {
                                intr->npoints = nin;
                                intr->points = in;
                                got_intr = 1;
                        }
                }

                last = a;
                if (a == n) break;
        }

        /* can't subtract something from nothing! */
        if (got_intr)
                *head = intr;
        else
                return;
        
        /* find the first item to subtract */
        for (a=0; a<n; a++)
                if (!mask[a]) break;

        if (a == n) return;
        last = a;

        /* and subtract it */
        diff = NULL;
        __clip(intr->points, intr->npoints,
                                base[last]->points, base[last]->npoints, 
                                &in, &nin, &out, &nout);

        crFree(in);

        for (a=0; a<base[last]->npoints; a++)   
        {
                if (!nout[a]) continue;

                p = (CRPoly *)crAlloc(sizeof(CRPoly));
                p->npoints = nout[a];
                p->points  = out[a];
                p->next = diff;
                diff = p;
        }
        *head = diff;

        while (1)
        {
                intr = diff;
                diff = NULL;

                for (a=last+1; a<n; a++)
                        if (!mask[a]) break;
                if (a == n) return;

                last = a;

                /* subtract mask[a] from everything in intr and
                 * plop it into diff */
                while (intr)
                {
                        __clip(intr->points, intr->npoints,
                                base[last]->points, base[last]->npoints, 
                                &in, &nin, &out, &nout);

                        crFree(in);

                        for (a=0; a<base[last]->npoints; a++)   
                        {
                                if (!nout[a]) continue;

                                p = (CRPoly *)crAlloc(sizeof(CRPoly));
                                p->npoints = nout[a];
                                p->points  = out[a];
                                p->next = diff;
                                diff = p;
                        }

                        intr = intr->next;
                }

                *head = diff;
        }       

}

/*
 * Here we generate all valid bitmaps to represent union/difference
 * combinations. Each bitmap is N elements long, where N is the 
 * number of polys [quads] that we are testing for overlap
 */
static void
__generate_masks(int n, int ***mask, int *nmasks)
{
        int a, b, c, d, e;
        int i, idx, isec_size, add;

        *mask = (int **)crAlloc((unsigned int)(1 << n)*sizeof(int));
        for (a=0; a<(1 << n); a++)
                (*mask)[a] = (int *)crAlloc(n*sizeof(int));

        /* compute combinations */
        idx = 0;
        for (isec_size=1; isec_size<n; isec_size++)
        {
                for (a=0; a<n; a++)
                {
                        for (b=a+1; b<n; b++)
                        {
                                crMemset((*mask)[idx], 0, n*sizeof(int));
                                (*mask)[idx][a] = 1;

                                add = 1;
                                for (c=0; c<isec_size; c++)
                                {
                                        i = (b+c) % n;
                                        if (i == a) add = 0;
                                                
                                        (*mask)[idx][i] = 1;    
                                }

                                /* dup check */
                                if ((add) && (idx))
                                {
                                        for (d=0; d<idx; d++)
                                        {
                                                add = 0;
                                                for (e=0; e<n; e++)
                                                {
                                                        if ((*mask)[idx][e] != (*mask)[d][e]) 
                                                                add = 1;
                                                }

                                                if (!add)
                                                        break;
                                        }
                                }

                                if (add) 
                                        idx++;
                        }
                }
        }

        *nmasks = idx;
}

/* 
 * To compute the overlap between a series of quads (This should work 
 * for n-gons, but we'll only need quads..), first generate a series of 
 * bitmaps that represent which elements to union together, and which
 * to difference. This goes into 'mask'. We then evaluate each bitmap with
 * Sutherland-Hodgman clipping to find the interior (union) and exterior
 * (difference) regions.
 *
 * In the map, 1 == union, 0 == difference
 *
 * (*res)[a] is the head of a poly list for all the polys that convert 
 * regions of overlap between a+1 polys ((*res)[0] == NULL)
 */ 
void
crComputeOverlapGeom(double *quads, int nquad, CRPoly ***res)
{
        int a, b, idx, isec_size, **mask;
        CRPoly *p, *next, **base;
        
        base = (CRPoly **)crAlloc(nquad*sizeof(CRPoly *));
        for (a=0; a<nquad; a++)
        {
                p = (CRPoly *)crAlloc(sizeof(CRPoly));
                p->npoints = 4;
                p->points  = (double *)crAlloc(8*sizeof(double));
                for (b=0; b<8; b++)
                {
                        p->points[b] = quads[8*a+b];
                }
                p->next = NULL;
                base[a] = p;
        }
        
        *res = (CRPoly **)crAlloc(nquad*sizeof(CRPoly *));
        for (a=0; a<nquad; a++)
                (*res)[a] = NULL;
        
        __generate_masks(nquad, &mask, &idx);

        for (a=0; a<idx; a++)
        {
                isec_size = 0;
                for (b=0; b<nquad; b++)
                        if (mask[a][b]) isec_size++;
                isec_size--;

                __execute_combination(base, nquad, mask[a], &p);
        
                while (p)
                {
                        next = p->next;
                        
                        p->next = (*res)[isec_size];
                        (*res)[isec_size] = p;
                        
                        p = next;
                }
        }

        for (a=0; a<nquad; a++)
        {
                crFree(base[a]->points);
                crFree(base[a]);
        }
        crFree(base);           

}

/*
 * This is similar to ComputeOverlapGeom above, but for "knockout" 
 * edge blending. 
 *
 * my_quad_idx is an index of quads indicating which display tile 
 * we are computing geometry for. From this, we either generate
 * geometry, or not, such that all geometry can be drawn in black 
 * and only one tile will show through the blend as non-black.
 *
 * To add a combination to our set of geom, we must test that:
 *              + mask[a][my_quad_idx] is set
 *              + mask[a][my_quad_idx] is not the first element set in
 *                      mask[a].
 * If these conditions hold, execute mask[a] and draw the resulting
 * geometry in black
 *
 * Unlike ComputeOverlapGeom, res is just a list of polys to draw in black
 */     
void
crComputeKnockoutGeom(double *quads, int nquad, int my_quad_idx, CRPoly **res)
{
        int a, b, idx, first, **mask;
        CRPoly *p, *next, **base;
        
        base = (CRPoly **) crAlloc(nquad*sizeof(CRPoly *));
        for (a=0; a<nquad; a++)
        {
                p = (CRPoly *) crAlloc(sizeof(CRPoly));
                p->npoints = 4;
                p->points  = (double *) crAlloc(8*sizeof(double));
                for (b=0; b<8; b++)
                {
                        p->points[b] = quads[8*a+b];
                }
                p->next = NULL;
                base[a] = p;
        }
        
        (*res) = NULL;
        
        __generate_masks(nquad, &mask, &idx);

        for (a=0; a<idx; a++)
        {
                /* test for above conditions */
                if (!mask[a][my_quad_idx]) continue;    

                first = -1;
                for (b=0; b<nquad; b++)
                        if (mask[a][b]) 
                        {
                                first = b;
                                break;
                        }
                if (first == my_quad_idx) continue;


                __execute_combination(base, nquad, mask[a], &p);
        
                while (p)
                {
                        next = p->next;
                        
                        p->next = *res;
                        *res = p;
                        
                        p = next;
                }
        }

        for (a=0; a<nquad; a++)
        {
                crFree(base[a]->points);
                crFree(base[a]);
        }
        crFree(base);           
}