gvld.c

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/*!
   \file lib/ogsf/gvld.c

   \brief OGSF library - loading and manipulating volumes (lower level functions)

   GRASS OpenGL gsurf OGSF Library 

   (C) 1999-2008 by the GRASS Development Team

   This program is free software under the 
   GNU General Public License (>=v2). 
   Read the file COPYING that comes with GRASS
   for details.

   \author Tomas Paudits (February 2004)
   \author Doxygenized by Martin Landa <landa.martin gmail.com> (May 2008)
 */

#include <math.h>

#include <grass/gis.h>
#include <grass/ogsf.h>

#include "mc33_table.h"

/* useful macros */
#define READ() gvl_read_char(pos[i]++, gvl->isosurf[i]->data)

/*!
   \brief Draw volume set (slices and isosurfaces)

   \param gvl pointer to geovol struct

   \return -1 on failure
   \return 1 on success
 */
int gvld_vol(geovol *gvl)
{
    G_debug(5, "gvld_vol(): id=%d", gvl->gvol_id);

    /* SLICES */
    /* calculate slices data, if slices changed */
    if (0 > gvl_slices_calc(gvl))
        return (-1);
    /* draw slices */
    if (0 > gvld_slices(gvl))
        return (-1);

    /* ISOSURFACES */
    /* calculate isosurfaces data, if isosurfaces changed */
    if (0 > gvl_isosurf_calc(gvl))
        return (-1);
    /* draw isosurfaces */
    if (0 > gvld_isosurf(gvl))
        return (-1);

    return (1);
}

/*!
   \brief Draw volume in wire mode (bounding box)

   \param gvl pointer to geovol struct

   \return -1 on failure
   \return 1 on success
 */
int gvld_wire_vol(geovol * gvl)
{
    G_debug(5, "gvld_wire_vol(): id=%d", gvl->gvol_id);

    gvld_wind3_box(gvl);

    if (0 > gvld_wire_slices(gvl))
        return (-1);

    if (0 > gvld_wire_isosurf(gvl))
        return (-1);

    return (1);
}

/*!
   \brief Draw volume isosurfaces

   \param gvl pointer to geovol struct

   \return -1 on failure
   \return 1 on success
 */
int gvld_isosurf(geovol * gvl)
{
    float tx, ty, tz;
    int cols, rows, depths;
    int x, y, z, i, iv;
    float xc, yc, zc;
    float xres, yres, zres;
    unsigned r, g, b;

    int j, p, num, c_ndx, crnt_ev;
    float n[3], pt[4];

    int n_i = gvl->n_isosurfs;

    int *check_color, *check_transp, *check_material, *check_emis,
        *check_shin;
    float *kem, *ksh, pkem, pksh;
    unsigned int *ktrans, *curcolor;
    int pktransp = 0;

    int *pos, *nz, *e_dl, tmp_pos, edge_pos[13];

    GLdouble modelMatrix[16], projMatrix[16];
    GLint viewport[4];
    GLint window[4];

    geovol_isosurf *isosurf;

    /* Allocate memory for arrays */

    check_color = G_malloc(n_i * sizeof(int));
    check_transp = G_malloc(n_i * sizeof(int));
    check_material = G_malloc(n_i * sizeof(int));
    check_emis = G_malloc(n_i * sizeof(int));
    check_shin = G_malloc(n_i * sizeof(int));

    kem = G_malloc(n_i * sizeof(float));
    ksh = G_malloc(n_i * sizeof(float));

    ktrans = G_malloc(n_i * sizeof(unsigned int));
    curcolor = G_malloc(n_i * sizeof(unsigned int));

    pos = G_malloc(n_i * sizeof(int));
    nz = G_malloc(n_i * sizeof(int));
    e_dl = G_malloc(n_i * sizeof(int));

    G_debug(5, "gvld_isosurf():");
    for (i = 0; i < gvl->n_isosurfs; i++) {
        G_debug(5, "  start : gvl: %s isosurf : %d\n",
                gvl_file_get_name(gvl->hfile), i);
    }

    /* shade */
    gsd_shademodel(gvl->isosurf_draw_mode & DM_GOURAUD);

    /* scaling */
    GS_get_scale(&tx, &ty, &tz, 1);

    /* set number of cols, rows, dephs */
    cols = gvl->cols / gvl->isosurf_x_mod;
    rows = gvl->rows / gvl->isosurf_y_mod;
    depths = gvl->depths / gvl->isosurf_z_mod;

    /* set x,y,z resolution */
    xres =
        /*((float) gvl->cols) / ((float) cols) */ gvl->isosurf_x_mod *
        gvl->xres;
    yres =
        /*((float) gvl->rows) / ((float) rows) */ gvl->isosurf_y_mod *
        gvl->yres;
    zres =
        /*((float) gvl->depths) / ((float) depths) */ gvl->isosurf_z_mod *
        gvl->zres;

    /* get viewport */
    gsd_getwindow(window, viewport, modelMatrix, projMatrix);

    /* adjust window */
    window[0] += (int)(yres * 2);
    window[1] -= (int)(yres * 2);
    window[2] -= (int)(xres * 2);
    window[3] += (int)(xres * 2);

    gsd_colormode(CM_DIFFUSE);
    gsd_pushmatrix();
    gsd_do_scale(1);
    gsd_translate(gvl->x_trans, gvl->y_trans, gvl->z_trans);

    pkem = 1.0;
    pksh = 1.0;

    /* set default attribute values for isosurfaces */
    for (i = 0; i < gvl->n_isosurfs; i++) {
        isosurf = gvl->isosurf[i];

        /* init isosurf one cube edge datalength */
        e_dl[i] = 4;

        /* transparency */
        check_transp[i] = 0;
        ktrans[i] = (255 << 24);
        if (CONST_ATT == isosurf->att[ATT_TRANSP].att_src &&
            isosurf->att[ATT_TRANSP].constant != 0.0) {
            ktrans[i] = (255 - (int)isosurf->att[ATT_TRANSP].constant) << 24;
        }
        else if (MAP_ATT == isosurf->att[ATT_TRANSP].att_src) {
            check_transp[i] = 1;
            e_dl[i]++;
        }

        /* emis */
        check_emis[i] = 0;
        kem[i] = 0.0;
        if (CONST_ATT == isosurf->att[ATT_EMIT].att_src) {
            kem[i] = isosurf->att[ATT_EMIT].constant / 255.;
        }
        else if (MAP_ATT == isosurf->att[ATT_EMIT].att_src) {
            check_emis[i] = 1;
            e_dl[i]++;
        }

        /* shin */
        check_shin[i] = 0;
        ksh[i] = 0.0;
        if (CONST_ATT == isosurf->att[ATT_SHINE].att_src) {
            ksh[i] = isosurf->att[ATT_SHINE].constant / 255.;
        }
        else if (MAP_ATT == isosurf->att[ATT_SHINE].att_src) {
            check_shin[i] = 1;
            e_dl[i]++;
        }

        /* color */
        check_color[i] = 0;
        curcolor[i] = 0.0;
        if (CONST_ATT == isosurf->att[ATT_COLOR].att_src) {
            curcolor[i] = (int)isosurf->att[ATT_COLOR].constant;
        }
        else if (MAP_ATT == isosurf->att[ATT_COLOR].att_src) {
            check_color[i] = 1;
            e_dl[i] += 3;
        }

        /* check material */
        check_material[i] = (check_shin[i] || check_emis[i] ||
                             (kem[i] && check_color[i]));

        /* set position in data */
        pos[i] = 0;
        nz[i] = 0;
    }

    G_debug(5, "  initialize OK");

    for (z = 0; z < depths - 1; z++) {
        zc = z * zres;

        if (GS_check_cancel()) {
            for (i = 0; i < gvl->n_isosurfs; i++) {
                G_debug(5, "  break : isosurf : %d datalength : %d B\n",
                        i, pos[i]);
            }

            gsd_set_material(1, 1, 0., 0., 0x0);
            gsd_popmatrix();
            gsd_blend(0);
            gsd_zwritemask(0xffffffff);

            return (-1);
        }

        for (y = 0; y < rows - 1; y++) {
            yc = ((rows - 1) * yres) - (y * yres);

            for (x = 0; x < cols - 1; x++) {
                xc = x * xres;

                for (i = 0; i < gvl->n_isosurfs; i++) {

                    /* read cube index */
                    if (nz[i] != 0) {
                        nz[i]--;
                        continue;
                    }
                    else {
                        c_ndx = READ();
                        if (c_ndx == 0) {
                            nz[i] = READ() - 1;
                            continue;
                        }
                        else {
                            c_ndx = (c_ndx - 1) * 256 + READ();
                        }
                    }

                    /* save position */
                    tmp_pos = pos[i];

                    /* set position for each cube edge data */
                    iv = 0;
                    for (j = 0; j < cell_table[c_ndx].nedges; j++) {
                        if (cell_table[c_ndx].edges[j] == 12)
                            iv = 1;

                        edge_pos[cell_table[c_ndx].edges[j]] =
                            pos[i] + j * e_dl[i];
                    }

                    /* enable/disable blending and depth buffer writing */
                    if (check_transp[i] || (ktrans[i] >> 24) < 255) {
                        if (!pktransp) {
                            gsd_blend(1);
                            gsd_zwritemask(0);
                        }
                    }
                    else if (pktransp) {
                        gsd_blend(0);
                        gsd_zwritemask(0xffffffff);
                        pktransp = 0;
                    }

                    /* draw cube polygons */
                    for (p = 0, num = 0; num < cell_table[c_ndx].npolys;
                         num++) {
                        gsd_bgnpolygon();

                        for (j = 0; j < 3; j++) {
                            crnt_ev = cell_table[c_ndx].polys[p];
                            /* set position in data to current edge data */
                            pos[i] = edge_pos[crnt_ev];

                            /* triagle vertex */
                            if (crnt_ev == 12) {
                                pt[X] = xc + (READ() / 255. * xres);
                                pt[Y] = yc + (-(READ() / 255. * yres));
                                pt[Z] = zc + (READ() / 255. * zres);
                            }
                            else {
                                pt[edge_vert_pos[crnt_ev][0]] = READ() / 255.;
                                pt[edge_vert_pos[crnt_ev][1]] =
                                    edge_vert_pos[crnt_ev][2];
                                pt[edge_vert_pos[crnt_ev][3]] =
                                    edge_vert_pos[crnt_ev][4];

                                pt[X] = xc + (pt[X] * xres);
                                pt[Y] = yc + (-(pt[Y] * yres));
                                pt[Z] = zc + (pt[Z] * zres);
                            }

                            n[X] = (READ() / 127. - 1.) / xres;
                            n[Y] = (-(READ() / 127. - 1.)) / yres;
                            n[Z] = (READ() / 127. - 1.) / zres;

                            if (gvl->isosurf[i]->inout_mode) {
                                n[X] *= -1;
                                n[Y] *= -1;
                                n[Z] *= -1;
                            }

                            if (check_color[i]) {
                                r = READ();
                                g = READ();
                                b = READ();
                                curcolor[i] =
                                    (r & 0xff) | ((g & 0xff) << 8) |
                                    ((b & 0xff) << 16);
                            }

                            if (check_transp[i])
                                ktrans[i] = READ() << 24;;

                            if (check_shin[i])
                                ksh[i] = ((float)READ()) / 255.;

                            if (check_emis[i])
                                kem[i] = ((float)READ()) / 255.;

                            if (pksh != ksh[i] || pkem != kem[i] ||
                                (kem[i] && check_color[i])) {
                                pksh = ksh[i];
                                pkem = kem[i];
                                gsd_set_material(1, 1, ksh[i], kem[i],
                                                 curcolor[i]);
                            }

                            gsd_litvert_func(n, ktrans[i] | curcolor[i], pt);
                            p++;
                        }

                        gsd_endpolygon();
                    }

                    /* set position to next cube */
                    pos[i] =
                        tmp_pos + cell_table[c_ndx].nedges * e_dl[i] +
                        (iv ? 2 : 0);
                }

            }

        }

    }

    for (i = 0; i < gvl->n_isosurfs; i++) {
        G_debug(5, "  end : isosurf : %d datalength : %d B\n", i, pos[i]);
    }

    gsd_set_material(1, 1, 0., 0., 0x0);
    gsd_popmatrix();
    gsd_blend(0);
    gsd_zwritemask(0xffffffff);

    return (0);
}

/*!
   \brief Draw volume isosurface in draw mode

   \param gvl pointer to geovol struct

   \return 0
 */
int gvld_wire_isosurf(geovol * gvl)
{
    return (0);
}

/************************************************************************/
/* SLICES */

/************************************************************************/

#define DISTANCE_2(x1, y1, x2, y2)      sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))

/*!
   \brief Draw slices

   \param gvl pointer to geovol struct

   \return 0
 */
int gvld_slices(geovol * gvl)
{
    float tx, ty, tz;
    int i;

    GLdouble modelMatrix[16], projMatrix[16];
    GLint viewport[4];
    GLint window[4];

    G_debug(5, "gvld_slices");

    /* shade */
    gsd_shademodel(gvl->slice_draw_mode & DM_GOURAUD);

    /* scaling */
    GS_get_scale(&tx, &ty, &tz, 1);

    /* get viewport */
    gsd_getwindow(window, viewport, modelMatrix, projMatrix);

    gsd_colormode(CM_COLOR);
    gsd_pushmatrix();
    gsd_do_scale(1);
    gsd_translate(gvl->x_trans, gvl->y_trans, gvl->z_trans);

    for (i = 0; i < gvl->n_slices; i++) {
        gsd_blend(0);
        gsd_zwritemask(0xffffffff);

        if (gvl->slice[i]->transp == 0)
            gvld_slice(gvl, i);
    }

    for (i = 0; i < gvl->n_slices; i++) {
        gsd_blend(1);
        gsd_zwritemask(0x0);

        if (gvl->slice[i]->transp > 0)
            gvld_slice(gvl, i);
    }

    gsd_set_material(1, 1, 0., 0., 0x0);
    gsd_popmatrix();
    gsd_blend(0);
    gsd_zwritemask(0xffffffff);

    return (0);
}

/*!
   \brief Draw slice

   \param gvl pointer to geovol struct
   \param ndx

   \return 1
 */
int gvld_slice(geovol * gvl, int ndx)
{
    geovol_slice *slice;

    int color, offset, transp;
    float n[3], pt[4];
    float x, nextx, y, nexty, z, stepx, stepy, stepz;
    int cols, rows, c, r;
    float f_cols, f_rows, distxy, distz, modx, mody, modz, modxy;
    int ptX, ptY, ptZ;
    double resx, resy, resz;

    /* current slice */
    slice = gvl->slice[ndx];

    /* distance between slice def. pts */
    distxy = DISTANCE_2(slice->x2, slice->y2, slice->x1, slice->y1);
    distz = fabsf(slice->z2 - slice->z1);

    /* distance between slice def pts is zero - zero slice */
    if (distxy == 0. || distz == 0.) {
        return (1);
    }

    /* set slice mod, resolution and set correct coords */
    if (slice->dir == X) {
        modx = gvl->slice_y_mod;
        mody = gvl->slice_z_mod;
        modz = gvl->slice_x_mod;
        resx = gvl->yres;
        resy = gvl->zres;
        resz = gvl->xres;
        ptX = Y;
        ptY = Z;
        ptZ = X;
    }
    else if (slice->dir == Y) {
        modx = gvl->slice_x_mod;
        mody = gvl->slice_z_mod;
        modz = gvl->slice_y_mod;
        resx = gvl->xres;
        resy = gvl->zres;
        resz = gvl->yres;
        ptX = X;
        ptY = Z;
        ptZ = Y;
    }
    else {
        modx = gvl->slice_x_mod;
        mody = gvl->slice_y_mod;
        modz = gvl->slice_z_mod;
        resx = gvl->xres;
        resy = gvl->yres;
        resz = gvl->zres;
        ptX = X;
        ptY = Y;
        ptZ = Z;
    }

    /* x,y mod */
    modxy =
        DISTANCE_2((slice->x2 - slice->x1) / distxy * modx,
                   (slice->y2 - slice->y1) / distxy * mody, 0., 0.);

    /* cols/rows of slice */
    f_cols = distxy / modxy;
    cols = f_cols > (int)f_cols ? (int)f_cols + 1 : (int)f_cols;

    f_rows = distz / modz;
    rows = f_rows > (int)f_rows ? (int)f_rows + 1 : (int)f_rows;

    /* step in x,y for each row of slice */
    stepx = (slice->x2 - slice->x1) / f_cols;
    stepy = (slice->y2 - slice->y1) / f_cols;
    stepz = (slice->z2 - slice->z1) / f_rows;

    /* set x,y initially to first slice pt */
    x = (slice->x1);
    y = (slice->y1);

    /* set next draw pt */
    if (f_cols < 1.) {
        nextx = x + stepx * f_cols;
        nexty = y + stepy * f_cols;
    }
    else {
        nextx = x + stepx;
        nexty = y + stepy;
    }

    /* set transparency */
    if (slice->transp > 0) {
        transp = (255 - slice->transp) << 24;
    }
    else {
        transp = 0x0;
    }

    /* loop in slice cols */
    for (c = 0; c < cols; c++) {

        /* set z to slice z1 pt */
        z = slice->z1;

        /* begin draw one row - triangle strip */
        gsd_bgntmesh();

        /* loop in slice rows */
        for (r = 0; r < rows + 1; r++) {
            /* offset to data - 1. column */
            offset = (c + 1) * (rows + 1) * 3 + r * 3;

            /* get color from slice data */
            color = (slice->data[offset] & 0xff) |
                ((slice->data[offset + 1] & 0xff) << 8) |
                ((slice->data[offset + 2] & 0xff) << 16);

            /* triagle vertices */
            pt[ptX] = nextx * resx;
            pt[ptY] = nexty * resy;
            pt[ptZ] = z * resz;

            pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
            gsd_litvert_func(n, (unsigned int)transp | color, pt);

            /* offset to data - 2. column */
            offset = c * (rows + 1) * 3 + r * 3;

            /* get color from slice data */
            color = (slice->data[offset] & 0xff) |
                ((slice->data[offset + 1] & 0xff) << 8) |
                ((slice->data[offset + 2] & 0xff) << 16);

            /* set triangle vertices */
            pt[ptX] = x * resx;
            pt[ptY] = y * resy;
            pt[ptZ] = z * resz;

            pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
            gsd_litvert_func(n, (unsigned int)transp | color, pt);

            if (r + 1 > f_rows) {
                z += stepz * (f_rows - (float)r);
            }
            else {
                z += stepz;
            }
        }

        gsd_endtmesh();

        /* step */
        if (c + 2 > f_cols) {
            x += stepx;
            nextx += stepx * (f_cols - (float)(c + 1));
            y += stepy;
            nexty += stepy * (f_cols - (float)(c + 1));
        }
        else {
            x += stepx;
            nextx += stepx;
            y += stepy;
            nexty += stepy;
        }
    }

    gsd_blend(0);
    gsd_zwritemask(0xffffffff);

    return (1);
}

/*!
   \brief Draw wire slices 

   \param gvl pointer to geovol struct

   \return 0
 */
int gvld_wire_slices(geovol * gvl)
{
    float pt[3];
    int i;
    int ptX, ptY, ptZ;
    double resx, resy, resz;

    geovol_slice *slice;

    G_debug(5, "gvld_wire_slices");

    gsd_pushmatrix();

    /* shading */
    gsd_shademodel(DM_FLAT);
    /* set color mode */
    gsd_colormode(CM_COLOR);
    /* do scale and set volume position */
    gsd_do_scale(1);
    gsd_translate(gvl->x_trans, gvl->y_trans, gvl->z_trans);

    /* set color and line width */
    gsd_color_func(0x0);
    gsd_linewidth(1);

    /* loop in slices */
    for (i = 0; i < gvl->n_slices; i++) {
        slice = gvl->slice[i];

        /* initialize correct coords */
        if (slice->dir == X) {
            resx = gvl->yres;
            resy = gvl->zres;
            resz = gvl->xres;
            ptX = Y;
            ptY = Z;
            ptZ = X;
        }
        else if (slice->dir == Y) {
            resx = gvl->xres;
            resy = gvl->zres;
            resz = gvl->yres;
            ptX = X;
            ptY = Z;
            ptZ = Y;
        }
        else {
            resx = gvl->xres;
            resy = gvl->yres;
            resz = gvl->zres;
            ptX = X;
            ptY = Y;
            ptZ = Z;
        }

        gsd_bgnline();

        /* first slice edge */
        pt[ptX] = slice->x1 * resx;
        pt[ptY] = slice->y1 * resy;
        pt[ptZ] = slice->z1 * resz;;
        pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
        gsd_vert_func(pt);

        pt[ptX] = slice->x1 * resx;
        pt[ptY] = slice->y1 * resy;
        pt[ptZ] = slice->z2 * resz;;
        pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
        gsd_vert_func(pt);

        pt[ptX] = slice->x2 * resx;
        pt[ptY] = slice->y2 * resy;
        pt[ptZ] = slice->z2 * resz;;
        pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
        gsd_vert_func(pt);

        pt[ptX] = slice->x2 * resx;
        pt[ptY] = slice->y2 * resy;
        pt[ptZ] = slice->z1 * resz;;
        pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
        gsd_vert_func(pt);

        pt[ptX] = slice->x1 * resx;
        pt[ptY] = slice->y1 * resy;
        pt[ptZ] = slice->z1 * resz;;
        pt[Y] = (gvl->rows - 1) * gvl->yres - pt[Y];
        gsd_vert_func(pt);

        gsd_endline();
    }

    gsd_set_material(1, 1, 0., 0., 0x0);
    gsd_popmatrix();

    return (0);
}

/*!
   \brief Draw volume bounding box

   \param gvl pointer to geovol struct

   \return 0
 */
int gvld_wind3_box(geovol * gvl)
{
    float pt[3];

    G_debug(5, "gvld_wind3_box(): id=%d", gvl->gvol_id);

    gsd_pushmatrix();

    /* shading */
    gsd_shademodel(DM_FLAT);
    /* set color mode */
    gsd_colormode(CM_COLOR);
    /* do scale and set volume position */
    gsd_do_scale(1);
    gsd_translate(gvl->x_trans, gvl->y_trans, gvl->z_trans);

    /* set color and line width */
    gsd_color_func(0x0);
    gsd_linewidth(1);

    /* draw box */

    /* front edges */
    gsd_bgnline();
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = 0;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = 0;
    gsd_vert_func(pt);
    gsd_endline();

    /* back edges */
    gsd_bgnline();
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = 0;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    gsd_endline();

    /* others edges */
    gsd_bgnline();
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = 0;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    gsd_endline();

    gsd_bgnline();
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = 0;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = 0;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    gsd_endline();

    gsd_bgnline();
    pt[X] = 0;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = 0;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    gsd_endline();

    gsd_bgnline();
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = 0;
    gsd_vert_func(pt);
    pt[X] = (gvl->cols - 1) * gvl->xres;
    pt[Y] = (gvl->rows - 1) * gvl->yres;
    pt[Z] = (gvl->depths - 1) * gvl->zres;
    gsd_vert_func(pt);
    gsd_endline();

    gsd_popmatrix();

    return (0);
}