[Bf-blender-cvs] [c6aacd718a5] master: Cleanup: Improve precision during UV packing.
Chris Blackbourn
noreply at git.blender.org
Tue Nov 8 20:51:59 CET 2022
Commit: c6aacd718a51dea2f0736280a6bd605898a320f2
Author: Chris Blackbourn
Date: Wed Nov 9 08:37:14 2022 +1300
Branches: master
https://developer.blender.org/rBc6aacd718a51dea2f0736280a6bd605898a320f2
Cleanup: Improve precision during UV packing.
Simplify API and improve accuracy of uv packing placement
by using pre-translation and double precision internally.
Will protect against future precision problems with UDIM.
No user visible changes expected.
Maniphest Tasks: T68889
Differential Revision: https://developer.blender.org/D16362
===================================================================
M source/blender/bmesh/intern/bmesh_query_uv.cc
M source/blender/bmesh/intern/bmesh_query_uv.h
M source/blender/editors/uvedit/uvedit_islands.cc
===================================================================
diff --git a/source/blender/bmesh/intern/bmesh_query_uv.cc b/source/blender/bmesh/intern/bmesh_query_uv.cc
index 33b2ca7a828..0e2385ff4e2 100644
--- a/source/blender/bmesh/intern/bmesh_query_uv.cc
+++ b/source/blender/bmesh/intern/bmesh_query_uv.cc
@@ -113,17 +113,6 @@ void BM_face_uv_minmax(const BMFace *f, float min[2], float max[2], const int cd
} while ((l_iter = l_iter->next) != l_first);
}
-void BM_face_uv_transform(BMFace *f, const float matrix[2][2], const int cd_loop_uv_offset)
-{
- BMLoop *l_iter;
- BMLoop *l_first;
- l_iter = l_first = BM_FACE_FIRST_LOOP(f);
- do {
- MLoopUV *luv = (MLoopUV *)BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset);
- mul_m2_v2(matrix, luv->uv);
- } while ((l_iter = l_iter->next) != l_first);
-}
-
bool BM_loop_uv_share_edge_check(BMLoop *l_a, BMLoop *l_b, const int cd_loop_uv_offset)
{
BLI_assert(l_a->e == l_b->e);
diff --git a/source/blender/bmesh/intern/bmesh_query_uv.h b/source/blender/bmesh/intern/bmesh_query_uv.h
index 2b0833f9185..6aa82653535 100644
--- a/source/blender/bmesh/intern/bmesh_query_uv.h
+++ b/source/blender/bmesh/intern/bmesh_query_uv.h
@@ -34,7 +34,6 @@ float BM_face_uv_calc_cross(const BMFace *f, int cd_loop_uv_offset) ATTR_WARN_UN
ATTR_NONNULL();
void BM_face_uv_minmax(const BMFace *f, float min[2], float max[2], int cd_loop_uv_offset);
-void BM_face_uv_transform(BMFace *f, const float matrix[2][2], int cd_loop_uv_offset);
bool BM_loop_uv_share_edge_check_with_limit(BMLoop *l_a,
BMLoop *l_b,
diff --git a/source/blender/editors/uvedit/uvedit_islands.cc b/source/blender/editors/uvedit/uvedit_islands.cc
index 92745667505..d8e10435146 100644
--- a/source/blender/editors/uvedit/uvedit_islands.cc
+++ b/source/blender/editors/uvedit/uvedit_islands.cc
@@ -36,29 +36,48 @@
#include "bmesh.h"
-/* -------------------------------------------------------------------- */
-/** \name UV Face Utilities
- * \{ */
+static void mul_v2_m2_add_v2v2(float r[2],
+ const float mat[2][2],
+ const float a[2],
+ const float b[2])
+{
+ /* Compute `r = mat * (a + b)` with high precision. */
+ const double x = static_cast<double>(a[0]) + static_cast<double>(b[0]);
+ const double y = static_cast<double>(a[1]) + static_cast<double>(b[1]);
+
+ r[0] = static_cast<float>(mat[0][0] * x + mat[1][0] * y);
+ r[1] = static_cast<float>(mat[0][1] * x + mat[1][1] * y);
+}
-static void bm_face_uv_translate_and_scale_around_pivot(BMFace *f,
- const float offset[2],
- const float scale[2],
- const float pivot[2],
- const int cd_loop_uv_offset)
+static void island_uv_transform(FaceIsland *island,
+ const float matrix[2][2], /* Scale and rotation. */
+ const float pre_translate[2] /* (pre) Translation. */
+)
{
- BMLoop *l_iter;
- BMLoop *l_first;
- l_iter = l_first = BM_FACE_FIRST_LOOP(f);
- do {
- MLoopUV *luv = static_cast<MLoopUV *>(BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset));
- for (int i = 0; i < 2; i++) {
- luv->uv[i] = offset[i] + (((luv->uv[i] - pivot[i]) * scale[i]) + pivot[i]);
+ /* Use a pre-transform to compute `A * (x+b)`
+ *
+ * \note Ordinarily, we'd use a post_transform like `A * x + b`
+ * In general, post-transforms are easier to work with when using homogenous co-ordinates.
+ *
+ * When UV mapping into the unit square, post-transforms can lose precision on small islands.
+ * Instead we're using a pre-transform to maintain precision.
+ *
+ * To convert post-transform to pre-transform, use `A * x + b == A * (x + c), c = A^-1 * b`
+ */
+
+ const int cd_loop_uv_offset = island->cd_loop_uv_offset;
+ const int faces_len = island->faces_len;
+ for (int i = 0; i < faces_len; i++) {
+ BMFace *f = island->faces[i];
+ BMLoop *l;
+ BMIter iter;
+ BM_ITER_ELEM (l, &iter, f, BM_LOOPS_OF_FACE) {
+ MLoopUV *luv = (MLoopUV *)BM_ELEM_CD_GET_VOID_P(l, cd_loop_uv_offset);
+ mul_v2_m2_add_v2v2(luv->uv, matrix, luv->uv, pre_translate);
}
- } while ((l_iter = l_iter->next) != l_first);
+ }
}
-/** \} */
-
/* -------------------------------------------------------------------- */
/** \name UV Face Array Utilities
* \{ */
@@ -198,13 +217,12 @@ static void face_island_uv_rotate_fit_aabb(FaceIsland *island)
/* Apply rotation back to BMesh. */
if (angle != 0.0f) {
float matrix[2][2];
+ float pre_translate[2] = {0, 0};
angle_to_mat2(matrix, angle);
matrix[1][0] *= 1.0f / aspect_y;
/* matrix[1][1] *= aspect_y / aspect_y; */
matrix[0][1] *= aspect_y;
- for (int i = 0; i < faces_len; i++) {
- BM_face_uv_transform(faces[i], matrix, cd_loop_uv_offset);
- }
+ island_uv_transform(island, matrix, pre_translate);
}
}
@@ -769,21 +787,24 @@ void ED_uvedit_pack_islands_multi(const Scene *scene,
}
}
+ float matrix[2][2];
+ float matrix_inverse[2][2];
+ float pre_translate[2];
for (int i = 0; i < island_vector.size(); i++) {
FaceIsland *island = island_vector[box_array[i].index];
- const float pivot[2] = {
- island->bounds_rect.xmin,
- island->bounds_rect.ymin,
- };
- const float offset[2] = {
- ((box_array[i].x * scale[0]) - island->bounds_rect.xmin) + base_offset[0],
- ((box_array[i].y * scale[1]) - island->bounds_rect.ymin) + base_offset[1],
- };
- for (int j = 0; j < island->faces_len; j++) {
- BMFace *efa = island->faces[j];
- bm_face_uv_translate_and_scale_around_pivot(
- efa, offset, scale, pivot, island->cd_loop_uv_offset);
- }
+ matrix[0][0] = scale[0];
+ matrix[0][1] = 0.0f;
+ matrix[1][0] = 0.0f;
+ matrix[1][1] = scale[1];
+ invert_m2_m2(matrix_inverse, matrix);
+
+ /* Add base_offset, post transform. */
+ mul_v2_m2v2(pre_translate, matrix_inverse, base_offset);
+
+ /* Translate to box_array from bounds_rect. */
+ pre_translate[0] += box_array[i].x - island->bounds_rect.xmin;
+ pre_translate[1] += box_array[i].y - island->bounds_rect.ymin;
+ island_uv_transform(island, matrix, pre_translate);
}
for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
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