svbsp.c

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// Shadow Volume BSP code written by Ashley Rose Hale (LadyHavoc) on 2003-11-06 and placed into public domain.
// Modified by LadyHavoc (to make it work and other nice things like that) on 2007-01-24 and 2007-01-25
// Optimized by LadyHavoc on 2009-12-24 and 2009-12-25
 
#include <math.h>
#include <string.h>
#include "svbsp.h"
#include "polygon.h"
 
#define MAX_SVBSP_POLYGONPOINTS 64
#define SVBSP_CLIP_EPSILON (1.0f / 1024.0f)
 
#define SVBSP_DotProduct(a,b) ((a)[0]*(b)[0]+(a)[1]*(b)[1]+(a)[2]*(b)[2])
 
typedef struct svbsp_polygon_s
{
    float points[MAX_SVBSP_POLYGONPOINTS][3];
    //unsigned char splitflags[MAX_SVBSP_POLYGONPOINTS];
    int facesplitflag;
    int numpoints;
}
typedef struct svbsp_polygon_s {…};
svbsp_polygon_t;
 
static void SVBSP_PlaneFromPoints(float *plane4f, const float *p1, const float *p2, const float *p3)
{
    float ilength;
    // calculate unnormalized plane
    plane4f[0] = (p1[1] - p2[1]) * (p3[2] - p2[2]) - (p1[2] - p2[2]) * (p3[1] - p2[1]);
    plane4f[1] = (p1[2] - p2[2]) * (p3[0] - p2[0]) - (p1[0] - p2[0]) * (p3[2] - p2[2]);
    plane4f[2] = (p1[0] - p2[0]) * (p3[1] - p2[1]) - (p1[1] - p2[1]) * (p3[0] - p2[0]);
    plane4f[3] = SVBSP_DotProduct(plane4f, p1);
    // normalize the plane normal and adjust distance accordingly
    ilength = (float)sqrt(SVBSP_DotProduct(plane4f, plane4f));
    if (ilength)
        ilength = 1.0f / ilength;
    plane4f[0] *= ilength;
    plane4f[1] *= ilength;
    plane4f[2] *= ilength;
    plane4f[3] *= ilength;
}
static void SVBSP_PlaneFromPoints(float *plane4f, const float *p1, const float *p2, const float *p3) {…}
 
static void SVBSP_DividePolygon(const svbsp_polygon_t *poly, const float *plane, svbsp_polygon_t *front, svbsp_polygon_t *back, const float *dists, const int *sides)
{
    int i, j, count = poly->numpoints, frontcount = 0, backcount = 0;
    float frac, ifrac, c[3], pdist, ndist;
    const float *nextpoint;
    const float *points = poly->points[0];
    float *outfront = front->points[0];
    float *outback = back->points[0];
    for(i = 0;i < count;i++, points += 3)
    {
        j = i + 1;
        if (j >= count)
            j = 0;
        if (!(sides[i] & 2))
        {
            outfront[frontcount*3+0] = points[0];
            outfront[frontcount*3+1] = points[1];
            outfront[frontcount*3+2] = points[2];
            frontcount++;
        }
        if (!(sides[i] & 1))
        {
            outback[backcount*3+0] = points[0];
            outback[backcount*3+1] = points[1];
            outback[backcount*3+2] = points[2];
            backcount++;
        }
        if ((sides[i] | sides[j]) == 3)
        {
            // don't allow splits if remaining points would overflow point buffer
            if (frontcount + (count - i) > MAX_SVBSP_POLYGONPOINTS - 1)
                continue;
            if (backcount + (count - i) > MAX_SVBSP_POLYGONPOINTS - 1)
                continue;
            nextpoint = poly->points[j];
            pdist = dists[i];
            ndist = dists[j];
            frac = pdist / (pdist - ndist);
            ifrac = 1.0f - frac;
            c[0] = points[0] * ifrac + frac * nextpoint[0];
            c[1] = points[1] * ifrac + frac * nextpoint[1];
            c[2] = points[2] * ifrac + frac * nextpoint[2];
            outfront[frontcount*3+0] = c[0];
            outfront[frontcount*3+1] = c[1];
            outfront[frontcount*3+2] = c[2];
            frontcount++;
            outback[backcount*3+0] = c[0];
            outback[backcount*3+1] = c[1];
            outback[backcount*3+2] = c[2];
            backcount++;
        }
    }
    front->numpoints = frontcount;
    back->numpoints = backcount;
}
static void SVBSP_DividePolygon(const svbsp_polygon_t *poly, const float *plane, svbsp_polygon_t *front, svbsp_polygon_t *back, const float *dists, const int *sides) {…}
 
void SVBSP_Init(svbsp_t *b, const float *origin, int maxnodes, svbsp_node_t *nodes)
{
    memset(b, 0, sizeof(*b));
    b->origin[0] = origin[0];
    b->origin[1] = origin[1];
    b->origin[2] = origin[2];
    b->numnodes = 3;
    b->maxnodes = maxnodes;
    b->nodes = nodes;
    b->ranoutofnodes = 0;
    b->stat_occluders_rejected = 0;
    b->stat_occluders_accepted = 0;
    b->stat_occluders_fragments_accepted = 0;
    b->stat_occluders_fragments_rejected = 0;
    b->stat_queries_rejected = 0;
    b->stat_queries_accepted = 0;
    b->stat_queries_fragments_accepted = 0;
    b->stat_queries_fragments_rejected = 0;
 
    // the bsp tree must be initialized to have two perpendicular splits axes
    // through origin, otherwise the polygon insertions would affect the
    // opposite side of the tree, which would be disasterous.
    //
    // so this code has to make 3 nodes and 4 leafs, and since the leafs are
    // represented by empty/solid state numbers in this system rather than
    // actual structs, we only need to make the 3 nodes.
 
    // root node
    // this one splits the world into +X and -X sides
    b->nodes[0].plane[0] = 1;
    b->nodes[0].plane[1] = 0;
    b->nodes[0].plane[2] = 0;
    b->nodes[0].plane[3] = origin[0];
    b->nodes[0].parent = -1;
    b->nodes[0].children[0] = 1;
    b->nodes[0].children[1] = 2;
 
    // +X side node
    // this one splits the +X half of the world into +Y and -Y
    b->nodes[1].plane[0] = 0;
    b->nodes[1].plane[1] = 1;
    b->nodes[1].plane[2] = 0;
    b->nodes[1].plane[3] = origin[1];
    b->nodes[1].parent = 0;
    b->nodes[1].children[0] = -1;
    b->nodes[1].children[1] = -1;
 
    // -X side node
    // this one splits the -X half of the world into +Y and -Y
    b->nodes[2].plane[0] = 0;
    b->nodes[2].plane[1] = 1;
    b->nodes[2].plane[2] = 0;
    b->nodes[2].plane[3] = origin[1];
    b->nodes[2].parent = 0;
    b->nodes[2].children[0] = -1;
    b->nodes[2].children[1] = -1;
}
void SVBSP_Init(svbsp_t *b, const float *origin, int maxnodes, svbsp_node_t *nodes) {…}
 
static void SVBSP_InsertOccluderPolygonNodes(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, const svbsp_polygon_t *poly, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
{
    // now we need to create up to numpoints + 1 new nodes, forming a BSP tree
    // describing the occluder polygon's shadow volume
    int i, j, p;
    svbsp_node_t *node;
 
    // points and lines are valid testers but not occluders
    if (poly->numpoints < 3)
        return;
 
    // if there aren't enough nodes remaining, skip it
    if (b->numnodes + poly->numpoints + 1 >= b->maxnodes)
    {
        b->ranoutofnodes = 1;
        return;
    }
 
    // add one node per side, then the actual occluding face node
 
    // thread safety notes:
    // DO NOT multithread insertion, it could be made 'safe' but the results
    // would be inconsistent.
    //
    // it is completely safe to multithread queries in all cases.
    //
    // if an insertion is occurring the query will give intermediate results,
    // being blocked by some volumes but not others, which is perfectly okay
    // for visibility culling intended only to reduce rendering work
 
    // note down the first available nodenum for the *parentnodenumpointer
    // line which is done last to allow multithreaded queries during an
    // insertion
    for (i = 0, p = poly->numpoints - 1;i < poly->numpoints;p = i, i++)
    {
#if 1
        // see if a parent plane describes this side
        for (j = parentnodenum;j >= 0;j = b->nodes[j].parent)
        {
            float *parentnodeplane = b->nodes[j].plane;
            if (fabs(SVBSP_DotProduct(poly->points[p], parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
             && fabs(SVBSP_DotProduct(poly->points[i], parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
             && fabs(SVBSP_DotProduct(b->origin      , parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON)
                break;
        }
        if (j >= 0)
            continue; // already have a matching parent plane
#endif
#if 0
        // skip any sides that were classified as belonging to a parent plane
        if (poly->splitflags[i])
            continue;
#endif
        // create a side plane
        // anything infront of this is not inside the shadow volume
        node = b->nodes + b->numnodes++;
        SVBSP_PlaneFromPoints(node->plane, b->origin, poly->points[p], poly->points[i]);
        // we need to flip the plane if it puts any part of the polygon on the
        // wrong side
        // (in this way this code treats all polygons as float sided)
        //
        // because speed is important this stops as soon as it finds proof
        // that the orientation is right or wrong
        // (we know that the plane is on one edge of the polygon, so there is
        // never a case where points lie on both sides, so the first hint is
        // sufficient)
        for (j = 0;j < poly->numpoints;j++)
        {
            float d = SVBSP_DotProduct(poly->points[j], node->plane) - node->plane[3];
            if (d < -SVBSP_CLIP_EPSILON)
                break;
            if (d > SVBSP_CLIP_EPSILON)
            {
                node->plane[0] *= -1;
                node->plane[1] *= -1;
                node->plane[2] *= -1;
                node->plane[3] *= -1;
                break;
            }
        }
        node->parent = parentnodenum;
        node->children[0] = -1; // empty
        node->children[1] = -1; // empty
        // link this child into the tree
        *parentnodenumpointer = parentnodenum = (int)(node - b->nodes);
        // now point to the child pointer for the next node to update later
        parentnodenumpointer = &node->children[1];
    }
 
#if 1
    // skip the face plane if it lies on a parent plane
    if (!poly->facesplitflag)
#endif
    {
        // add the face-plane node
        // infront is empty, behind is shadow
        node = b->nodes + b->numnodes++;
        SVBSP_PlaneFromPoints(node->plane, poly->points[0], poly->points[1], poly->points[2]);
        // this is a flip check similar to the one above
        // this one checks if the plane faces the origin, if not, flip it
        if (SVBSP_DotProduct(b->origin, node->plane) - node->plane[3] < -SVBSP_CLIP_EPSILON)
        {
            node->plane[0] *= -1;
            node->plane[1] *= -1;
            node->plane[2] *= -1;
            node->plane[3] *= -1;
        }
        node->parent = parentnodenum;
        node->children[0] = -1; // empty
        node->children[1] = -2; // shadow
        // link this child into the tree
        // (with the addition of this node, queries will now be culled by it)
        *parentnodenumpointer = (int)(node - b->nodes);
    }
}
static void SVBSP_InsertOccluderPolygonNodes(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, const svbsp_polygon_t *poly, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1) {…}
 
static int SVBSP_AddPolygonNode(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, const svbsp_polygon_t *poly, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
{
    int i;
    int s;
    int facesplitflag = poly->facesplitflag;
    int bothsides;
    float plane[4];
    float d;
    svbsp_polygon_t front;
    svbsp_polygon_t back;
    svbsp_node_t *node;
    int sides[MAX_SVBSP_POLYGONPOINTS];
    float dists[MAX_SVBSP_POLYGONPOINTS];
    if (poly->numpoints < 1)
        return 0;
    // recurse through plane nodes
    while (*parentnodenumpointer >= 0)
    {
        // get node info
        parentnodenum = *parentnodenumpointer;
        node = b->nodes + parentnodenum;
        plane[0] = node->plane[0];
        plane[1] = node->plane[1];
        plane[2] = node->plane[2];
        plane[3] = node->plane[3];
        // calculate point dists for clipping
        bothsides = 0;
        for (i = 0;i < poly->numpoints;i++)
        {
            d = SVBSP_DotProduct(poly->points[i], plane) - plane[3];
            s = 0;
            if (d > SVBSP_CLIP_EPSILON)
                s = 1;
            if (d < -SVBSP_CLIP_EPSILON)
                s = 2;
            bothsides |= s;
            dists[i] = d;
            sides[i] = s;
        }
        // see which side the polygon is on
        switch(bothsides)
        {
        default:
        case 0:
            // no need to split, this polygon is on the plane
            // this case only occurs for polygons on the face plane, usually
            // the same polygon (inserted twice - once as occluder, once as
            // tester)
            // if this is an occluder, it is redundant
            if (insertoccluder)
                return 1; // occluded
            // if this is a tester, test the front side, because it is
            // probably the same polygon that created this node...
            facesplitflag = 1;
            parentnodenumpointer = &node->children[0];
            continue;
        case 1:
            // no need to split, just go to one side
            parentnodenumpointer = &node->children[0];
            continue;
        case 2:
            // no need to split, just go to one side
            parentnodenumpointer = &node->children[1];
            continue;
        case 3:
            // lies on both sides of the plane, we need to split it
#if 1
            SVBSP_DividePolygon(poly, plane, &front, &back, dists, sides);
#else
            PolygonF_Divide(poly->numpoints, poly->points[0], plane[0], plane[1], plane[2], plane[3], SVBSP_CLIP_EPSILON, MAX_SVBSP_POLYGONPOINTS, front.points[0], &front.numpoints, MAX_SVBSP_POLYGONPOINTS, back.points[0], &back.numpoints, NULL);
            if (front.numpoints > MAX_SVBSP_POLYGONPOINTS)
                front.numpoints = MAX_SVBSP_POLYGONPOINTS;
            if (back.numpoints > MAX_SVBSP_POLYGONPOINTS)
                back.numpoints = MAX_SVBSP_POLYGONPOINTS;
#endif
            front.facesplitflag = facesplitflag;
            back.facesplitflag = facesplitflag;
            // recurse the sides and return the resulting occlusion flags
            i  = SVBSP_AddPolygonNode(b, &node->children[0], *parentnodenumpointer, &front, insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
            i |= SVBSP_AddPolygonNode(b, &node->children[1], *parentnodenumpointer, &back , insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
            return i;
        }
    }
    // leaf node
    if (*parentnodenumpointer == -1)
    {
        // empty leaf node; and some geometry survived
        // if inserting an occluder, replace this empty leaf with a shadow volume
#if 0
        for (i = 0;i < poly->numpoints-2;i++)
        {
            Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
            Debug_PolygonVertex(poly->points[  0][0], poly->points[  0][1], poly->points[  0][2], 0.0f, 0.0f, 0.25f, 0.0f, 0.0f, 1.0f);
            Debug_PolygonVertex(poly->points[i+1][0], poly->points[i+1][1], poly->points[i+1][2], 0.0f, 0.0f, 0.25f, 0.0f, 0.0f, 1.0f);
            Debug_PolygonVertex(poly->points[i+2][0], poly->points[i+2][1], poly->points[i+2][2], 0.0f, 0.0f, 0.25f, 0.0f, 0.0f, 1.0f);
            Debug_PolygonEnd();
        }
#endif
        if (insertoccluder)
        {
            b->stat_occluders_fragments_accepted++;
            SVBSP_InsertOccluderPolygonNodes(b, parentnodenumpointer, parentnodenum, poly, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
        }
        else
            b->stat_queries_fragments_accepted++;
        if (fragmentcallback)
            fragmentcallback(fragmentcallback_pointer1, fragmentcallback_number1, b, poly->numpoints, poly->points[0]);
        return 2;
    }
    else
    {
        // otherwise it's a solid leaf which destroys all polygons inside it
        if (insertoccluder)
            b->stat_occluders_fragments_rejected++;
        else
            b->stat_queries_fragments_rejected++;
#if 0
        for (i = 0;i < poly->numpoints-2;i++)
        {
            Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
            Debug_PolygonVertex(poly->points[  0][0], poly->points[  0][1], poly->points[  0][2], 0.0f, 0.0f, 0.0f, 0.0f, 0.25f, 1.0f);
            Debug_PolygonVertex(poly->points[i+1][0], poly->points[i+1][1], poly->points[i+1][2], 0.0f, 0.0f, 0.0f, 0.0f, 0.25f, 1.0f);
            Debug_PolygonVertex(poly->points[i+2][0], poly->points[i+2][1], poly->points[i+2][2], 0.0f, 0.0f, 0.0f, 0.0f, 0.25f, 1.0f);
            Debug_PolygonEnd();
        }
#endif
    }
    return 1;
}
static int SVBSP_AddPolygonNode(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, const svbsp_polygon_t *poly, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1) {…}
 
int SVBSP_AddPolygon(svbsp_t *b, int numpoints, const float *points, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
{
    int i;
    int nodenum;
    svbsp_polygon_t poly;
    // don't even consider an empty polygon
    // note we still allow points and lines to be tested...
    if (numpoints < 1)
        return 0;
    // if the polygon has too many points, we would crash
    if (numpoints > MAX_SVBSP_POLYGONPOINTS)
        return 0;
    poly.numpoints = numpoints;
    for (i = 0;i < numpoints;i++)
    {
        poly.points[i][0] = points[i*3+0];
        poly.points[i][1] = points[i*3+1];
        poly.points[i][2] = points[i*3+2];
        //poly.splitflags[i] = 0; // this edge is a valid BSP splitter - clipped edges are not (because they lie on a bsp plane)
        poly.facesplitflag = 0; // this face is a valid BSP Splitter - if it lies on a bsp plane it is not
    }
#if 0
//if (insertoccluder)
    for (i = 0;i < poly.numpoints-2;i++)
    {
        Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
        Debug_PolygonVertex(poly.points[  0][0], poly.points[  0][1], poly.points[  0][2], 0.0f, 0.0f, 0.0f, 0.25f, 0.0f, 1.0f);
        Debug_PolygonVertex(poly.points[i+1][0], poly.points[i+1][1], poly.points[i+1][2], 0.0f, 0.0f, 0.0f, 0.25f, 0.0f, 1.0f);
        Debug_PolygonVertex(poly.points[i+2][0], poly.points[i+2][1], poly.points[i+2][2], 0.0f, 0.0f, 0.0f, 0.25f, 0.0f, 1.0f);
        Debug_PolygonEnd();
    }
#endif
    nodenum = 0;
    i = SVBSP_AddPolygonNode(b, &nodenum, -1, &poly, insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
    if (insertoccluder)
    {
        if (i & 2)
            b->stat_occluders_accepted++;
        else
            b->stat_occluders_rejected++;
    }
    else
    {
        if (i & 2)
            b->stat_queries_accepted++;
        else
            b->stat_queries_rejected++;
    }
    return i;
}
int SVBSP_AddPolygon(svbsp_t *b, int numpoints, const float *points, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const float *points), void *fragmentcallback_pointer1, int fragmentcallback_number1) {…}