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Fix unreported: Add tie-break conditions for udim search with integers 

When searching for closest UDIM with integer co-ordinates, several UDIMs
can be equidistant. Previously, of all closest UDIMs, the one which was
earliest in the list would be used. Now, "half-open interval" rules are
used to break the tie.

Motivated by 0fcc04e7bf

Differential Revision: https://developer.blender.org/D15590
This commit is contained in:
Chris Blackbourn 2022-08-01 17:00:10 +12:00
parent 43918ec28d
commit 68c1eb86a6
1 changed files with 68 additions and 16 deletions
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84
source/blender/blenkernel/intern/image.cc
View File

@ -863,36 +863,88 @@ void BKE_image_get_tile_uv(const Image *ima, const int tile_number, float r_uv[2
}
}
/* Linear distance between #x and the unit interval. */
static float distance_to_unit_interval(float x)
{
/* The unit interval is between 0 and 1.
Within the interval, return 0.
Outside the interval, return the distance to the nearest boundary.
Intuitively, the function looks like:
\ | | /
__\|___|/__
0 1
*/
if (x <= 0.0f) {
return -x; /* Distance to left border. */
}
if (x <= 1.0f) {
return 0.0f; /* Inside unit interval. */
}
return x - 1.0f; /* Distance to right border. */
}
/* Distance squared between #co and the unit square with lower-left starting at #udim. */
static float distance_squared_to_udim(const float co[2], const float udim[2])
{
float delta[2];
sub_v2_v2v2(delta, co, udim);
delta[0] = distance_to_unit_interval(delta[0]);
delta[1] = distance_to_unit_interval(delta[1]);
return len_squared_v2(delta);
}
static bool nearest_udim_tile_tie_break(const float best_dist_sq,
const float best_uv[2],
const float dist_sq,
const float uv[2])
{
if (best_dist_sq == dist_sq) { /* Exact same distance? Tie-break. */
if (best_uv[0] == uv[0]) { /* Exact same U? Tie-break. */
return (uv[1] > best_uv[1]); /* Higher than previous candidate? */
}
return (uv[0] > best_uv[0]); /* Further right than previous candidate? */
}
return (dist_sq < best_dist_sq); /* Closer than previous candidate? */
}
/* Finds the nearest tile and offset to #co.
* If the co-ordinates are integers, take special care to break ties. */
int BKE_image_find_nearest_tile_with_offset(const Image *image,
const float co[2],
float r_uv_offset[2])
{
/* Distance squared to the closest UDIM tile. */
float dist_best_sq = FLT_MAX;
float uv_offset_best[2] = {0, 0};
zero_v2(r_uv_offset);
int tile_number_best = -1;
const float co_offset[2] = {co[0] - 0.5f, co[1] - 0.5f};
if (!image || image->source != IMA_SRC_TILED) {
return tile_number_best;
}
/* Distance squared to the closest UDIM tile. */
float dist_best_sq = FLT_MAX;
LISTBASE_FOREACH (const ImageTile *, tile, &image->tiles) {
float uv_offset[2];
BKE_image_get_tile_uv(image, tile->tile_number, uv_offset);
/* Distance squared between co[2] and center of UDIM tile. */
const float dist_sq = len_squared_v2v2(uv_offset, co_offset);
/* Distance squared between #co and closest point on UDIM tile. */
const float dist_sq = distance_squared_to_udim(co, uv_offset);
if (dist_sq < dist_best_sq) {
dist_best_sq = dist_sq;
tile_number_best = tile->tile_number;
copy_v2_v2(uv_offset_best, uv_offset);
if (dist_best_sq < 0.5f * 0.5f) {
break; /* No other tile can be closer. */
if (dist_sq == 0) { /* Either inside in the UDIM, or on its boundary. */
if (floorf(co[0]) == uv_offset[0] && floorf(co[1]) == uv_offset[1]) {
/* Within the half-open interval of the UDIM. */
copy_v2_v2(r_uv_offset, uv_offset);
return tile_number_best;
}
}
}
if (tile_number_best != -1) {
copy_v2_v2(r_uv_offset, uv_offset_best);
if (nearest_udim_tile_tie_break(dist_best_sq, r_uv_offset, dist_sq, uv_offset)) {
/* Tile is better than previous best, update. */
dist_best_sq = dist_sq;
copy_v2_v2(r_uv_offset, uv_offset);
tile_number_best = tile->tile_number;
}
}
return tile_number_best;
}