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more efficient atlas packing algorithm

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This commit is contained in:
Vasiliy Makarov 2017-08-24 13:17:27 +03:00
parent fb90ac8e48
commit bbf66945e7
1 changed files with 53 additions and 37 deletions
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90
editor/io_plugins/editor_atlas.cpp
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@ -47,21 +47,15 @@ struct _EditorAtlasWorkRectResult {
void EditorAtlas::fit(const Vector<Size2i> &p_rects, Vector<Point2i> &r_result, Size2i &r_size) {
//super simple, almost brute force scanline stacking fitter
//it's pretty basic for now, but it tries to make sure that the aspect ratio of the
//resulting atlas is somehow square. This is necesary because video cards have limits
//on texture size (usually 2048 or 4096), so the more square a texture, the more chances
//it will work in every hardware.
// for example, it will prioritize a 1024x1024 atlas (works everywhere) instead of a
// 256x8192 atlas (won't work anywhere).
ERR_FAIL_COND(p_rects.size() == 0);
Vector<_EditorAtlasWorkRect> wrects;
wrects.resize(p_rects.size());
long total_area = 0;
for (int i = 0; i < p_rects.size(); i++) {
wrects[i].s = p_rects[i];
wrects[i].idx = i;
total_area += p_rects[i].width * p_rects[i].height;
}
wrects.sort();
int widest = wrects[0].s.width;
@ -76,37 +70,59 @@ void EditorAtlas::fit(const Vector<Size2i> &p_rects, Vector<Point2i> &r_result,
if (w < widest)
continue;
Vector<int> hmax;
hmax.resize(w);
for (int j = 0; j < w; j++)
hmax[j] = 0;
//place them
int ofs = 0;
Vector<int> wmax;
wmax.resize(total_area / w);
for (int j = 0; j < wmax.size(); j++)
wmax[j] = 0;
for (int j = 0; j < wrects.size(); j++) {
if (ofs + wrects[j].s.width > w) {
int new_x = 0;
int new_y = 0;
ofs = 0;
}
int piece_w = wrects[j].s.width;
int piece_h = wrects[j].s.height;
int from_y = 0;
for (int k = 0; k < wrects[j].s.width; k++) {
bool found_place;
if (hmax[ofs + k] > from_y)
from_y = hmax[ofs + k];
}
do {
found_place = true;
new_x = 0;
if (wmax.size() <= new_y + piece_h) {
int prevS = wmax.size();
wmax.resize(new_y + piece_h + 128);
for (int k = prevS; k < wmax.size(); k++)
wmax[k] = 0;
}
for (int k = 0; k < piece_h; k++) {
if (new_x < wmax[new_y + k]) new_x = wmax[new_y + k];
if (new_x + piece_w > w) {
new_y += k + 1;
found_place = false;
break;
}
}
if (found_place) {
// one more check is calculating lost space of atlas
long lost_area = 0;
for (int k = 0; k < piece_h; k++) {
lost_area += new_x - wmax[new_y + k];
}
if (lost_area >= piece_w * piece_h / 2) {
found_place = false;
new_y++;
}
}
} while (!found_place);
wrects[j].p.x = ofs;
wrects[j].p.y = from_y;
wrects[j].p.x = new_x;
wrects[j].p.y = new_y;
int end_h = from_y + wrects[j].s.height;
int end_w = ofs + wrects[j].s.width;
int end_h = new_y + piece_h;
int end_w = new_x + piece_w;
for (int k = 0; k < wrects[j].s.width; k++) {
hmax[ofs + k] = end_h;
for (int k = 0; k < piece_h; k++) {
wmax[new_y + k] = end_w;
}
if (end_h > max_h)
@ -114,8 +130,6 @@ void EditorAtlas::fit(const Vector<Size2i> &p_rects, Vector<Point2i> &r_result,
if (end_w > max_w)
max_w = end_w;
ofs += wrects[j].s.width;
}
_EditorAtlasWorkRectResult result;
@ -123,21 +137,23 @@ void EditorAtlas::fit(const Vector<Size2i> &p_rects, Vector<Point2i> &r_result,
result.max_h = max_h;
result.max_w = max_w;
results.push_back(result);
float efficiency = float(max_w * max_h) / float(next_power_of_2(max_w) * next_power_of_2(max_h));
print_line("Processing atlas: width " + itos(w) + " ,height " + itos(max_h) + " ,efficiency " + rtos(efficiency));
}
//find the result with the best aspect ratio
//find the result with the most efficiency
int best = -1;
float best_aspect = 1e20;
float max_eff = 0;
for (int i = 0; i < results.size(); i++) {
float h = results[i].max_h;
float w = results[i].max_w;
float aspect = h > w ? h / w : w / h;
if (aspect < best_aspect) {
float efficiency = float(w * h) / float(next_power_of_2(w) * next_power_of_2(h));
if (efficiency > max_eff) {
best = i;
best_aspect = aspect;
max_eff = efficiency;
}
}