r_rast.c

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/*
Copyright (C) 1997-2001 Id Software, Inc.
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program 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 General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
*/
// r_rast.c
 
#include <assert.h>
 
#include "r_local.h"
 
#define MAXLEFTCLIPEDGES        100
 
// !!! if these are changed, they must be changed in asm_draw.h too !!!
#define FULLY_CLIPPED_CACHED    0x80000000
#define FRAMECOUNT_MASK         0x7FFFFFFF
 
unsigned int    cacheoffset;
 
int         c_faceclip;                 // number of faces clipped
 
 
clipplane_t *entity_clipplanes;
clipplane_t view_clipplanes[4];
clipplane_t world_clipplanes[16];
 
medge_t         *r_pedge;
 
qboolean        r_leftclipped, r_rightclipped;
static qboolean makeleftedge, makerightedge;
qboolean        r_nearzionly;
 
int     sintable[1280];
int     intsintable[1280];
int     blanktable[1280];       // PGM
 
mvertex_t   r_leftenter, r_leftexit;
mvertex_t   r_rightenter, r_rightexit;
 
typedef struct
{
    float   u,v;
    int     ceilv;
} evert_t;
 
int             r_emitted;
float           r_nearzi;
float           r_u1, r_v1, r_lzi1;
int             r_ceilv1;
 
qboolean        r_lastvertvalid;
int             r_skyframe;
 
msurface_t      *r_skyfaces;
mplane_t        r_skyplanes[6];
mtexinfo_t      r_skytexinfo[6];
mvertex_t       *r_skyverts;
medge_t         *r_skyedges;
int             *r_skysurfedges;
 
// I just copied this data from a box map...
int skybox_planes[12] = {2,-128, 0,-128, 2,128, 1,128, 0,128, 1,-128};
 
int box_surfedges[24] = { 1,2,3,4,  -1,5,6,7,  8,9,-6,10,  -2,-7,-9,11,
  12,-3,-11,-8,  -12,-10,-5,-4};
int box_edges[24] = { 1,2, 2,3, 3,4, 4,1, 1,5, 5,6, 6,2, 7,8, 8,6, 5,7, 8,3, 7,4};
 
int box_faces[6] = {0,0,2,2,2,0};
 
vec3_t  box_vecs[6][2] = {
    {   {0,-1,0}, {-1,0,0} },
    { {0,1,0}, {0,0,-1} },
    {   {0,-1,0}, {1,0,0} },
    { {1,0,0}, {0,0,-1} },
    { {0,-1,0}, {0,0,-1} },
    { {-1,0,0}, {0,0,-1} }
};
 
float   box_verts[8][3] = {
    {-1,-1,-1},
    {-1,1,-1},
    {1,1,-1},
    {1,-1,-1},
    {-1,-1,1},
    {-1,1,1},
    {1,-1,1},
    {1,1,1}
};
 
// down, west, up, north, east, south
// {"rt", "bk", "lf", "ft", "up", "dn"};
 
/*
================
R_InitSkyBox
 
================
*/
void R_InitSkyBox (void)
{
    int     i;
    extern model_t *loadmodel;
 
    r_skyfaces = loadmodel->surfaces + loadmodel->numsurfaces;
    loadmodel->numsurfaces += 6;
    r_skyverts = loadmodel->vertexes + loadmodel->numvertexes;
    loadmodel->numvertexes += 8;
    r_skyedges = loadmodel->edges + loadmodel->numedges;
    loadmodel->numedges += 12;
    r_skysurfedges = loadmodel->surfedges + loadmodel->numsurfedges;
    loadmodel->numsurfedges += 24;
    if (loadmodel->numsurfaces > MAX_MAP_FACES
        || loadmodel->numvertexes > MAX_MAP_VERTS
        || loadmodel->numedges > MAX_MAP_EDGES)
        ri.Sys_Error (ERR_DROP, "InitSkyBox: map overflow");
 
    memset (r_skyfaces, 0, 6*sizeof(*r_skyfaces));
    for (i=0 ; i<6 ; i++)
    {
        r_skyplanes[i].normal[skybox_planes[i*2]] = 1;
        r_skyplanes[i].dist = skybox_planes[i*2+1];
 
        VectorCopy (box_vecs[i][0], r_skytexinfo[i].vecs[0]);
        VectorCopy (box_vecs[i][1], r_skytexinfo[i].vecs[1]);
 
        r_skyfaces[i].plane = &r_skyplanes[i];
        r_skyfaces[i].numedges = 4;
        r_skyfaces[i].flags = box_faces[i] | SURF_DRAWSKYBOX;
        r_skyfaces[i].firstedge = loadmodel->numsurfedges-24+i*4;
        r_skyfaces[i].texinfo = &r_skytexinfo[i];
        r_skyfaces[i].texturemins[0] = -128;
        r_skyfaces[i].texturemins[1] = -128;
        r_skyfaces[i].extents[0] = 256;
        r_skyfaces[i].extents[1] = 256;
    }
 
    for (i=0 ; i<24 ; i++)
        if (box_surfedges[i] > 0)
            r_skysurfedges[i] = loadmodel->numedges-13 + box_surfedges[i];
        else
            r_skysurfedges[i] = - (loadmodel->numedges-13 + -box_surfedges[i]);
 
    for(i=0 ; i<12 ; i++)
    {
        r_skyedges[i].v[0] = loadmodel->numvertexes-9+box_edges[i*2+0];
        r_skyedges[i].v[1] = loadmodel->numvertexes-9+box_edges[i*2+1];
        r_skyedges[i].cachededgeoffset = 0;
    }
}
 
/*
================
R_EmitSkyBox
================
*/
void R_EmitSkyBox (void)
{
    int     i, j;
    int     oldkey;
 
    if (insubmodel)
        return;     // submodels should never have skies
    if (r_skyframe == r_framecount)
        return;     // already set this frame
 
    r_skyframe = r_framecount;
 
    // set the eight fake vertexes
    for (i=0 ; i<8 ; i++)
        for (j=0 ; j<3 ; j++)
            r_skyverts[i].position[j] = r_origin[j] + box_verts[i][j]*128;
 
    // set the six fake planes
    for (i=0 ; i<6 ; i++)
        if (skybox_planes[i*2+1] > 0)
            r_skyplanes[i].dist = r_origin[skybox_planes[i*2]]+128;
        else
            r_skyplanes[i].dist = r_origin[skybox_planes[i*2]]-128;
 
    // fix texture offseets
    for (i=0 ; i<6 ; i++)
    {
        r_skytexinfo[i].vecs[0][3] = -DotProduct (r_origin, r_skytexinfo[i].vecs[0]);
        r_skytexinfo[i].vecs[1][3] = -DotProduct (r_origin, r_skytexinfo[i].vecs[1]);
    }
 
    // emit the six faces
    oldkey = r_currentkey;
    r_currentkey = 0x7ffffff0;
    for (i=0 ; i<6 ; i++)
    {
        R_RenderFace (r_skyfaces + i, 15);
    }
    r_currentkey = oldkey;      // bsp sorting order
}
 
 
#if !id386
 
/*
================
R_EmitEdge
================
*/
void R_EmitEdge (mvertex_t *pv0, mvertex_t *pv1)
{
    edge_t  *edge, *pcheck;
    int     u_check;
    float   u, u_step;
    vec3_t  local, transformed;
    float   *world;
    int     v, v2, ceilv0;
    float   scale, lzi0, u0, v0;
    int     side;
 
    if (r_lastvertvalid)
    {
        u0 = r_u1;
        v0 = r_v1;
        lzi0 = r_lzi1;
        ceilv0 = r_ceilv1;
    }
    else
    {
        world = &pv0->position[0];
    
    // transform and project
        VectorSubtract (world, modelorg, local);
        TransformVector (local, transformed);
    
        if (transformed[2] < NEAR_CLIP)
            transformed[2] = NEAR_CLIP;
    
        lzi0 = 1.0 / transformed[2];
    
    // FIXME: build x/yscale into transform?
        scale = xscale * lzi0;
        u0 = (xcenter + scale*transformed[0]);
        if (u0 < r_refdef.fvrectx_adj)
            u0 = r_refdef.fvrectx_adj;
        if (u0 > r_refdef.fvrectright_adj)
            u0 = r_refdef.fvrectright_adj;
    
        scale = yscale * lzi0;
        v0 = (ycenter - scale*transformed[1]);
        if (v0 < r_refdef.fvrecty_adj)
            v0 = r_refdef.fvrecty_adj;
        if (v0 > r_refdef.fvrectbottom_adj)
            v0 = r_refdef.fvrectbottom_adj;
    
        ceilv0 = (int) ceil(v0);
    }
 
    world = &pv1->position[0];
 
// transform and project
    VectorSubtract (world, modelorg, local);
    TransformVector (local, transformed);
 
    if (transformed[2] < NEAR_CLIP)
        transformed[2] = NEAR_CLIP;
 
    r_lzi1 = 1.0 / transformed[2];
 
    scale = xscale * r_lzi1;
    r_u1 = (xcenter + scale*transformed[0]);
    if (r_u1 < r_refdef.fvrectx_adj)
        r_u1 = r_refdef.fvrectx_adj;
    if (r_u1 > r_refdef.fvrectright_adj)
        r_u1 = r_refdef.fvrectright_adj;
 
    scale = yscale * r_lzi1;
    r_v1 = (ycenter - scale*transformed[1]);
    if (r_v1 < r_refdef.fvrecty_adj)
        r_v1 = r_refdef.fvrecty_adj;
    if (r_v1 > r_refdef.fvrectbottom_adj)
        r_v1 = r_refdef.fvrectbottom_adj;
 
    if (r_lzi1 > lzi0)
        lzi0 = r_lzi1;
 
    if (lzi0 > r_nearzi)    // for mipmap finding
        r_nearzi = lzi0;
 
// for right edges, all we want is the effect on 1/z
    if (r_nearzionly)
        return;
 
    r_emitted = 1;
 
    r_ceilv1 = (int) ceil(r_v1);
 
 
// create the edge
    if (ceilv0 == r_ceilv1)
    {
    // we cache unclipped horizontal edges as fully clipped
        if (cacheoffset != 0x7FFFFFFF)
        {
            cacheoffset = FULLY_CLIPPED_CACHED |
                    (r_framecount & FRAMECOUNT_MASK);
        }
 
        return;     // horizontal edge
    }
 
    side = ceilv0 > r_ceilv1;
 
    edge = edge_p++;
 
    edge->owner = r_pedge;
 
    edge->nearzi = lzi0;
 
    if (side == 0)
    {
    // trailing edge (go from p1 to p2)
        v = ceilv0;
        v2 = r_ceilv1 - 1;
 
        edge->surfs[0] = surface_p - surfaces;
        edge->surfs[1] = 0;
 
        u_step = ((r_u1 - u0) / (r_v1 - v0));
        u = u0 + ((float)v - v0) * u_step;
    }
    else
    {
    // leading edge (go from p2 to p1)
        v2 = ceilv0 - 1;
        v = r_ceilv1;
 
        edge->surfs[0] = 0;
        edge->surfs[1] = surface_p - surfaces;
 
        u_step = ((u0 - r_u1) / (v0 - r_v1));
        u = r_u1 + ((float)v - r_v1) * u_step;
    }
 
    edge->u_step = u_step*0x100000;
    edge->u = u*0x100000 + 0xFFFFF;
 
// we need to do this to avoid stepping off the edges if a very nearly
// horizontal edge is less than epsilon above a scan, and numeric error causes
// it to incorrectly extend to the scan, and the extension of the line goes off
// the edge of the screen
// FIXME: is this actually needed?
    if (edge->u < r_refdef.vrect_x_adj_shift20)
        edge->u = r_refdef.vrect_x_adj_shift20;
    if (edge->u > r_refdef.vrectright_adj_shift20)
        edge->u = r_refdef.vrectright_adj_shift20;
 
//
// sort the edge in normally
//
    u_check = edge->u;
    if (edge->surfs[0])
        u_check++;  // sort trailers after leaders
 
    if (!newedges[v] || newedges[v]->u >= u_check)
    {
        edge->next = newedges[v];
        newedges[v] = edge;
    }
    else
    {
        pcheck = newedges[v];
        while (pcheck->next && pcheck->next->u < u_check)
            pcheck = pcheck->next;
        edge->next = pcheck->next;
        pcheck->next = edge;
    }
 
    edge->nextremove = removeedges[v2];
    removeedges[v2] = edge;
}
 
 
/*
================
R_ClipEdge
================
*/
void R_ClipEdge (mvertex_t *pv0, mvertex_t *pv1, clipplane_t *clip)
{
    float       d0, d1, f;
    mvertex_t   clipvert;
 
    if (clip)
    {
        do
        {
            d0 = DotProduct (pv0->position, clip->normal) - clip->dist;
            d1 = DotProduct (pv1->position, clip->normal) - clip->dist;
 
            if (d0 >= 0)
            {
            // point 0 is unclipped
                if (d1 >= 0)
                {
                // both points are unclipped
                    continue;
                }
 
            // only point 1 is clipped
 
            // we don't cache clipped edges
                cacheoffset = 0x7FFFFFFF;
 
                f = d0 / (d0 - d1);
                clipvert.position[0] = pv0->position[0] +
                        f * (pv1->position[0] - pv0->position[0]);
                clipvert.position[1] = pv0->position[1] +
                        f * (pv1->position[1] - pv0->position[1]);
                clipvert.position[2] = pv0->position[2] +
                        f * (pv1->position[2] - pv0->position[2]);
 
                if (clip->leftedge)
                {
                    r_leftclipped = true;
                    r_leftexit = clipvert;
                }
                else if (clip->rightedge)
                {
                    r_rightclipped = true;
                    r_rightexit = clipvert;
                }
 
                R_ClipEdge (pv0, &clipvert, clip->next);
                return;
            }
            else
            {
            // point 0 is clipped
                if (d1 < 0)
                {
                // both points are clipped
                // we do cache fully clipped edges
                    if (!r_leftclipped)
                        cacheoffset = FULLY_CLIPPED_CACHED |
                                (r_framecount & FRAMECOUNT_MASK);
                    return;
                }
 
            // only point 0 is clipped
                r_lastvertvalid = false;
 
            // we don't cache partially clipped edges
                cacheoffset = 0x7FFFFFFF;
 
                f = d0 / (d0 - d1);
                clipvert.position[0] = pv0->position[0] +
                        f * (pv1->position[0] - pv0->position[0]);
                clipvert.position[1] = pv0->position[1] +
                        f * (pv1->position[1] - pv0->position[1]);
                clipvert.position[2] = pv0->position[2] +
                        f * (pv1->position[2] - pv0->position[2]);
 
                if (clip->leftedge)
                {
                    r_leftclipped = true;
                    r_leftenter = clipvert;
                }
                else if (clip->rightedge)
                {
                    r_rightclipped = true;
                    r_rightenter = clipvert;
                }
 
                R_ClipEdge (&clipvert, pv1, clip->next);
                return;
            }
        } while ((clip = clip->next) != NULL);
    }
 
// add the edge
    R_EmitEdge (pv0, pv1);
}
 
#endif  // !id386
 
 
/*
================
R_EmitCachedEdge
================
*/
void R_EmitCachedEdge (void)
{
    edge_t      *pedge_t;
 
    pedge_t = (edge_t *)((unsigned long)r_edges + r_pedge->cachededgeoffset);
 
    if (!pedge_t->surfs[0])
        pedge_t->surfs[0] = surface_p - surfaces;
    else
        pedge_t->surfs[1] = surface_p - surfaces;
 
    if (pedge_t->nearzi > r_nearzi) // for mipmap finding
        r_nearzi = pedge_t->nearzi;
 
    r_emitted = 1;
}
 
 
/*
================
R_RenderFace
================
*/
void R_RenderFace (msurface_t *fa, int clipflags)
{
    int         i, lindex;
    unsigned    mask;
    mplane_t    *pplane;
    float       distinv;
    vec3_t      p_normal;
    medge_t     *pedges, tedge;
    clipplane_t *pclip;
 
    // translucent surfaces are not drawn by the edge renderer
    if (fa->texinfo->flags & (SURF_TRANS33|SURF_TRANS66))
    {
        fa->nextalphasurface = r_alpha_surfaces;
        r_alpha_surfaces = fa;
        return;
    }
 
    // sky surfaces encountered in the world will cause the
    // environment box surfaces to be emited
    if ( fa->texinfo->flags & SURF_SKY )
    {
        R_EmitSkyBox ();    
        return;
    }
 
// skip out if no more surfs
    if ((surface_p) >= surf_max)
    {
        r_outofsurfaces++;
        return;
    }
 
// ditto if not enough edges left, or switch to auxedges if possible
    if ((edge_p + fa->numedges + 4) >= edge_max)
    {
        r_outofedges += fa->numedges;
        return;
    }
 
    c_faceclip++;
 
// set up clip planes
    pclip = NULL;
 
    for (i=3, mask = 0x08 ; i>=0 ; i--, mask >>= 1)
    {
        if (clipflags & mask)
        {
            view_clipplanes[i].next = pclip;
            pclip = &view_clipplanes[i];
        }
    }
 
// push the edges through
    r_emitted = 0;
    r_nearzi = 0;
    r_nearzionly = false;
    makeleftedge = makerightedge = false;
    pedges = currentmodel->edges;
    r_lastvertvalid = false;
 
    for (i=0 ; i<fa->numedges ; i++)
    {
        lindex = currentmodel->surfedges[fa->firstedge + i];
 
        if (lindex > 0)
        {
            r_pedge = &pedges[lindex];
 
        // if the edge is cached, we can just reuse the edge
            if (!insubmodel)
            {
                if (r_pedge->cachededgeoffset & FULLY_CLIPPED_CACHED)
                {
                    if ((r_pedge->cachededgeoffset & FRAMECOUNT_MASK) ==
                        r_framecount)
                    {
                        r_lastvertvalid = false;
                        continue;
                    }
                }
                else
                {
                    if ((((unsigned long)edge_p - (unsigned long)r_edges) >
                         r_pedge->cachededgeoffset) &&
                        (((edge_t *)((unsigned long)r_edges +
                         r_pedge->cachededgeoffset))->owner == r_pedge))
                    {
                        R_EmitCachedEdge ();
                        r_lastvertvalid = false;
                        continue;
                    }
                }
            }
 
        // assume it's cacheable
            cacheoffset = (byte *)edge_p - (byte *)r_edges;
            r_leftclipped = r_rightclipped = false;
            R_ClipEdge (&r_pcurrentvertbase[r_pedge->v[0]],
                        &r_pcurrentvertbase[r_pedge->v[1]],
                        pclip);
            r_pedge->cachededgeoffset = cacheoffset;
 
            if (r_leftclipped)
                makeleftedge = true;
            if (r_rightclipped)
                makerightedge = true;
            r_lastvertvalid = true;
        }
        else
        {
            lindex = -lindex;
            r_pedge = &pedges[lindex];
        // if the edge is cached, we can just reuse the edge
            if (!insubmodel)
            {
                if (r_pedge->cachededgeoffset & FULLY_CLIPPED_CACHED)
                {
                    if ((r_pedge->cachededgeoffset & FRAMECOUNT_MASK) ==
                        r_framecount)
                    {
                        r_lastvertvalid = false;
                        continue;
                    }
                }
                else
                {
                // it's cached if the cached edge is valid and is owned
                // by this medge_t
                    if ((((unsigned long)edge_p - (unsigned long)r_edges) >
                         r_pedge->cachededgeoffset) &&
                        (((edge_t *)((unsigned long)r_edges +
                         r_pedge->cachededgeoffset))->owner == r_pedge))
                    {
                        R_EmitCachedEdge ();
                        r_lastvertvalid = false;
                        continue;
                    }
                }
            }
 
        // assume it's cacheable
            cacheoffset = (byte *)edge_p - (byte *)r_edges;
            r_leftclipped = r_rightclipped = false;
            R_ClipEdge (&r_pcurrentvertbase[r_pedge->v[1]],
                        &r_pcurrentvertbase[r_pedge->v[0]],
                        pclip);
            r_pedge->cachededgeoffset = cacheoffset;
 
            if (r_leftclipped)
                makeleftedge = true;
            if (r_rightclipped)
                makerightedge = true;
            r_lastvertvalid = true;
        }
    }
 
// if there was a clip off the left edge, add that edge too
// FIXME: faster to do in screen space?
// FIXME: share clipped edges?
    if (makeleftedge)
    {
        r_pedge = &tedge;
        r_lastvertvalid = false;
        R_ClipEdge (&r_leftexit, &r_leftenter, pclip->next);
    }
 
// if there was a clip off the right edge, get the right r_nearzi
    if (makerightedge)
    {
        r_pedge = &tedge;
        r_lastvertvalid = false;
        r_nearzionly = true;
        R_ClipEdge (&r_rightexit, &r_rightenter, view_clipplanes[1].next);
    }
 
// if no edges made it out, return without posting the surface
    if (!r_emitted)
        return;
 
    r_polycount++;
 
    surface_p->msurf = fa;
    surface_p->nearzi = r_nearzi;
    surface_p->flags = fa->flags;
    surface_p->insubmodel = insubmodel;
    surface_p->spanstate = 0;
    surface_p->entity = currententity;
    surface_p->key = r_currentkey++;
    surface_p->spans = NULL;
 
    pplane = fa->plane;
// FIXME: cache this?
    TransformVector (pplane->normal, p_normal);
// FIXME: cache this?
    distinv = 1.0 / (pplane->dist - DotProduct (modelorg, pplane->normal));
 
    surface_p->d_zistepu = p_normal[0] * xscaleinv * distinv;
    surface_p->d_zistepv = -p_normal[1] * yscaleinv * distinv;
    surface_p->d_ziorigin = p_normal[2] * distinv -
            xcenter * surface_p->d_zistepu -
            ycenter * surface_p->d_zistepv;
 
    surface_p++;
}
 
 
/*
================
R_RenderBmodelFace
================
*/
void R_RenderBmodelFace (bedge_t *pedges, msurface_t *psurf)
{
    int         i;
    unsigned    mask;
    mplane_t    *pplane;
    float       distinv;
    vec3_t      p_normal;
    medge_t     tedge;
    clipplane_t *pclip;
 
    if (psurf->texinfo->flags & (SURF_TRANS33|SURF_TRANS66))
    {
        psurf->nextalphasurface = r_alpha_surfaces;
        r_alpha_surfaces = psurf;
        return;
    }
 
// skip out if no more surfs
    if (surface_p >= surf_max)
    {
        r_outofsurfaces++;
        return;
    }
 
// ditto if not enough edges left, or switch to auxedges if possible
    if ((edge_p + psurf->numedges + 4) >= edge_max)
    {
        r_outofedges += psurf->numedges;
        return;
    }
 
    c_faceclip++;
 
// this is a dummy to give the caching mechanism someplace to write to
    r_pedge = &tedge;
 
// set up clip planes
    pclip = NULL;
 
    for (i=3, mask = 0x08 ; i>=0 ; i--, mask >>= 1)
    {
        if (r_clipflags & mask)
        {
            view_clipplanes[i].next = pclip;
            pclip = &view_clipplanes[i];
        }
    }
 
// push the edges through
    r_emitted = 0;
    r_nearzi = 0;
    r_nearzionly = false;
    makeleftedge = makerightedge = false;
// FIXME: keep clipped bmodel edges in clockwise order so last vertex caching
// can be used?
    r_lastvertvalid = false;
 
    for ( ; pedges ; pedges = pedges->pnext)
    {
        r_leftclipped = r_rightclipped = false;
        R_ClipEdge (pedges->v[0], pedges->v[1], pclip);
 
        if (r_leftclipped)
            makeleftedge = true;
        if (r_rightclipped)
            makerightedge = true;
    }
 
// if there was a clip off the left edge, add that edge too
// FIXME: faster to do in screen space?
// FIXME: share clipped edges?
    if (makeleftedge)
    {
        r_pedge = &tedge;
        R_ClipEdge (&r_leftexit, &r_leftenter, pclip->next);
    }
 
// if there was a clip off the right edge, get the right r_nearzi
    if (makerightedge)
    {
        r_pedge = &tedge;
        r_nearzionly = true;
        R_ClipEdge (&r_rightexit, &r_rightenter, view_clipplanes[1].next);
    }
 
// if no edges made it out, return without posting the surface
    if (!r_emitted)
        return;
 
    r_polycount++;
 
    surface_p->msurf = psurf;
    surface_p->nearzi = r_nearzi;
    surface_p->flags = psurf->flags;
    surface_p->insubmodel = true;
    surface_p->spanstate = 0;
    surface_p->entity = currententity;
    surface_p->key = r_currentbkey;
    surface_p->spans = NULL;
 
    pplane = psurf->plane;
// FIXME: cache this?
    TransformVector (pplane->normal, p_normal);
// FIXME: cache this?
    distinv = 1.0 / (pplane->dist - DotProduct (modelorg, pplane->normal));
 
    surface_p->d_zistepu = p_normal[0] * xscaleinv * distinv;
    surface_p->d_zistepv = -p_normal[1] * yscaleinv * distinv;
    surface_p->d_ziorigin = p_normal[2] * distinv -
            xcenter * surface_p->d_zistepu -
            ycenter * surface_p->d_zistepv;
 
    surface_p++;
}