109 lines
2.3 KiB
C++
109 lines
2.3 KiB
C++
#ifndef STAR_BLOCKS_ALONG_LINE_HPP
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#define STAR_BLOCKS_ALONG_LINE_HPP
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#include "StarVector.hpp"
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namespace Star {
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// Iterate over integral cells based on Bresenham's line drawing algorithm.
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// Returns false immediately when the callback returns false for any cell,
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// returns true after iterating through every cell otherwise.
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template <typename Scalar>
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bool forBlocksAlongLine(Vector<Scalar, 2> origin, Vector<Scalar, 2> const& dxdy, function<bool(int, int)> callback) {
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Vector<Scalar, 2> remote = origin + dxdy;
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double dx = dxdy[0];
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if (dx < 0)
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dx *= -1;
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double dy = dxdy[1];
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if (dy < 0)
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dy *= -1;
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double oxfloor = floor(origin[0]);
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double oyfloor = floor(origin[1]);
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double rxfloor = floor(remote[0]);
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double ryfloor = floor(remote[1]);
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if (dx == 0) {
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if (oyfloor < ryfloor) {
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for (int i = oyfloor; i <= ryfloor; ++i) {
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if (!callback(oxfloor, i))
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return false;
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}
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} else {
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for (int i = oyfloor; i >= ryfloor; --i) {
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if (!callback(oxfloor, i))
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return false;
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}
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}
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return true;
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} else if (dy == 0) {
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if (oxfloor < rxfloor) {
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for (int i = oxfloor; i <= rxfloor; ++i) {
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if (!callback(i, oyfloor))
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return false;
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}
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} else {
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for (int i = oxfloor; i >= rxfloor; --i) {
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if (!callback(i, oyfloor))
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return false;
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}
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}
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return true;
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} else {
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int x = oxfloor;
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int y = oyfloor;
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int n = 1;
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int x_inc, y_inc;
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double error;
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if (dxdy[0] > 0) {
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x_inc = 1;
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n += int(rxfloor) - x;
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error = (oxfloor + 1 - origin[0]) * dy;
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} else {
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x_inc = -1;
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n += x - int(rxfloor);
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error = (origin[0] - oxfloor) * dy;
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}
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if (dxdy[1] > 0) {
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y_inc = 1;
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n += int(ryfloor) - y;
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error -= (oyfloor + 1 - origin[1]) * dx;
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} else {
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y_inc = -1;
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n += y - int(ryfloor);
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error -= (origin[1] - oyfloor) * dx;
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}
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for (; n > 0; --n) {
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if (!callback(x, y))
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return false;
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if (error > 0) {
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y += y_inc;
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error -= dx;
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} else if (error < 0) {
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x += x_inc;
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error += dy;
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} else {
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--n;
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y += y_inc;
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x += x_inc;
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error += dy;
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error -= dx;
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}
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}
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return true;
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}
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}
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}
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#endif
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