C++ Bresenham 3d Line Drawing Algorithm

bresenham3d

// Bresenham3D
//
// A slightly modified version of the source found at
// http://www.ict.griffith.edu.au/anthony/info/graphics/bresenham.procs
// Provided by Anthony Thyssen, though he does not take credit for the original implementation
//
// It is highly likely that the original Author was Bob Pendelton, as referenced here
//
// ftp://ftp.isc.org/pub/usenet/comp.sources.unix/volume26/line3d
//
// line3d was dervied from DigitalLine.c published as "Digital Line Drawing"
// by Paul Heckbert from "Graphics Gems", Academic Press, 1990
//
// 3D modifications by Bob Pendleton. The original source code was in the public
// domain, the author of the 3D version places his modifications in the
// public domain as well.
//
// line3d uses Bresenham's algorithm to generate the 3 dimensional points on a
// line from (x1, y1, z1) to (x2, y2, z2)
//


void Bresenham3D(int x1, int y1, int z1, const int x2, const int y2, const int z2, WorldMap *output, int symbol){
    
    int i, dx, dy, dz, l, m, n, x_inc, y_inc, z_inc, err_1, err_2, dx2, dy2, dz2;
    int point[3];
    
    point[0] = x1;
    point[1] = y1;
    point[2] = z1;
    dx = x2 - x1;
    dy = y2 - y1;
    dz = z2 - z1;
    x_inc = (dx < 0) ? -1 : 1;
    l = abs(dx);
    y_inc = (dy < 0) ? -1 : 1;
    m = abs(dy);
    z_inc = (dz < 0) ? -1 : 1;
    n = abs(dz);
    dx2 = l << 1;
    dy2 = m << 1;
    dz2 = n << 1;
    
    if ((l >= m) && (l >= n)) {
        err_1 = dy2 - l;
        err_2 = dz2 - l;
        for (i = 0; i < l; i++) {
            output->getTileAt(point[0], point[1], point[2])->setSymbol(symbol);
            if (err_1 > 0) {
                point[1] += y_inc;
                err_1 -= dx2;
            }
            if (err_2 > 0) {
                point[2] += z_inc;
                err_2 -= dx2;
            }
            err_1 += dy2;
            err_2 += dz2;
            point[0] += x_inc;
        }
    } else if ((m >= l) && (m >= n)) {
        err_1 = dx2 - m;
        err_2 = dz2 - m;
        for (i = 0; i < m; i++) {
            output->getTileAt(point[0], point[1], point[2])->setSymbol(symbol);
            if (err_1 > 0) {
                point[0] += x_inc;
                err_1 -= dy2;
            }
            if (err_2 > 0) {
                point[2] += z_inc;
                err_2 -= dy2;
            }
            err_1 += dx2;
            err_2 += dz2;
            point[1] += y_inc;
        }
    } else {
        err_1 = dy2 - n;
        err_2 = dx2 - n;
        for (i = 0; i < n; i++) {
            output->getTileAt(point[0], point[1], point[2])->setSymbol(symbol);
            if (err_1 > 0) {
                point[1] += y_inc;
                err_1 -= dz2;
            }
            if (err_2 > 0) {
                point[0] += x_inc;
                err_2 -= dz2;
            }
            err_1 += dy2;
            err_2 += dx2;
            point[2] += z_inc;
        }
    }
    output->getTileAt(point[0], point[1], point[2])->setSymbol(symbol);
}

Hi,What if my coordinates x1.y1,z1 are of type ;double',then I am getting this : error C2296: '<<' : illegal, left operand has type 'double'
Can you please explain the way to rectify this error.

Also,if I want to use for a size of some 0.3 or 0.5,I want to fix one paramter 'resolution',Which can have any value like 0.3 or 0.5 or 1.
I think,your code only works for a grid size of 1,right?

@sriharsha48 That's what the Bresenham's line algorithm is all about; drawing a line on a grid. From Wikipedia:

Bresenham's line algorithm is an algorithm that determines the points of an n-dimensional raster that should be selected in order to form a close approximation to a straight line between two points.

It it supposed to only work with integer values... now, let's give it a try. :)

Seems to be working great! Many thanks @yamamushi!

If anyone's interested, the screenshot is from a level editor I'm working on called Edddy.

@Modanung glad you found it useful! Your level editor looks awesome by the way :)