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Fix #122896: Knife snap to edge fails when a vertex is behind the viewer

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Although c9fa73a379 made the problem worse. The incorrect to snap to
edges when one of their vertices is behind the viewer is much older.

The problem occurred because, in perspective mode, when we project a
vertex with negative "zfac", its projected value is undefined as it
depends on the position of the other vertex.

Thus, both the distance test and the lambda in these cases were wrong.

The solution was to calculate the snap point directly in 3D, using
`closest_ray_to_segment_v3` and avoiding projecting the edge.
This commit is contained in:
Germano Cavalcante
2024-06-08 12:08:52 -03:00
parent 85f026f478
commit efd3c4b3c9
1 changed files with 31 additions and 47 deletions
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78
source/blender/editors/mesh/editmesh_knife.cc
View File

@@ -115,8 +115,9 @@ struct KnifeVert {
* -1 represents the absence of an object. */
int ob_index;
float co[3], cageco[3];
bool is_cut; /* Along a cut created by user input (will draw too). */
float co[3]; /* Vertex position in the original mesh. Equivalent to #BMVert::co[3]. */
float cageco[3]; /* Vertex position in the Cage mesh and in World Space. */
bool is_cut; /* Along a cut created by user input (will draw too). */
bool is_invalid;
bool is_splitting; /* Created when an edge was split. */
};
@@ -3095,19 +3096,18 @@ static void knife_pos_data_clear(KnifePosData *kpd)
/** \name Snapping (#knife_snap_update_from_mval)
* \{ */
static bool knife_find_closest_face(KnifeTool_OpData *kcd, const float2 &mval, KnifePosData *r_kpd)
static bool knife_find_closest_face(KnifeTool_OpData *kcd,
const float3 ray_origin,
const float3 ray_normal,
const float2 &mval,
KnifePosData *r_kpd)
{
float3 cage;
int ob_index;
BMFace *f;
float dist = KMAXDIST;
float3 origin;
float3 ray_normal;
ED_view3d_win_to_ray_clipped(
kcd->vc.depsgraph, kcd->region, kcd->vc.v3d, mval, origin, ray_normal, false);
f = knife_bvh_raycast(kcd, origin, ray_normal, 0.0f, nullptr, cage, &ob_index);
f = knife_bvh_raycast(kcd, ray_origin, ray_normal, 0.0f, nullptr, cage, &ob_index);
if (f && kcd->only_select && BM_elem_flag_test(f, BM_ELEM_SELECT) == 0) {
f = nullptr;
@@ -3132,7 +3132,7 @@ static bool knife_find_closest_face(KnifeTool_OpData *kcd, const float2 &mval, K
/* Cheat for now; just put in the origin instead
* of a true coordinate on the face.
* This just puts a point 1.0f in front of the view. */
cage = origin + ray_normal;
cage = ray_origin + ray_normal;
ob_index = 0;
BLI_assert(ob_index == kcd->objects.first_index_of_try(vc.obact));
@@ -3230,7 +3230,6 @@ static bool knife_snap_edge_constrained(KnifeTool_OpData *kcd,
const float kfv1_sco[2],
const float kfv2_sco[2],
float *r_dist_sq,
float *r_lambda,
float2 &r_sco)
{
/* If snapping, check we're in bounds. */
@@ -3245,33 +3244,19 @@ static bool knife_snap_edge_constrained(KnifeTool_OpData *kcd,
float dis_sq = len_squared_v2v2(sco, r_sco);
if (dis_sq < *r_dist_sq) {
*r_dist_sq = dis_sq;
*r_lambda = lambda;
return true;
}
return false;
}
/* Use when lambda is in screen-space. */
static void knife_interp_v3_v3v3(const KnifeTool_OpData *kcd,
float r_co[3],
const float v1[3],
const float v2[3],
const float lambda_ss)
{
float lambda = lambda_ss;
if (!kcd->is_ortho) {
/* Adjust the lambda according to the perspective. */
float w1 = mul_project_m4_v3_zfac(kcd->vc.rv3d->persmat, v1);
float w2 = mul_project_m4_v3_zfac(kcd->vc.rv3d->persmat, v2);
lambda = (lambda_ss * w1) / (w2 + (lambda_ss * (w1 - w2)));
}
interp_v3_v3v3(r_co, v1, v2, lambda);
}
/* p is closest point on edge to the mouse cursor. */
static bool knife_find_closest_edge_of_face(
KnifeTool_OpData *kcd, int ob_index, BMFace *f, const float2 &cage_ss, KnifePosData *r_kpd)
static bool knife_find_closest_edge_of_face(KnifeTool_OpData *kcd,
int ob_index,
BMFace *f,
const float3 ray_origin,
const float3 ray_normal,
const float2 &mval,
KnifePosData *r_kpd)
{
float maxdist;
@@ -3295,7 +3280,6 @@ static bool knife_find_closest_edge_of_face(
LISTBASE_FOREACH (LinkData *, ref, list) {
KnifeEdge *kfe = static_cast<KnifeEdge *>(ref->data);
float kfv1_sco[2], kfv2_sco[2], test_cagep[3];
float lambda;
if (kfe->is_invalid) {
continue;
@@ -3313,26 +3297,21 @@ static bool knife_find_closest_edge_of_face(
(kcd->mode == MODE_DRAGGING))
{
dis_sq = cur_dist_sq;
if (!knife_snap_edge_constrained(
kcd, cage_ss, kfv1_sco, kfv2_sco, &dis_sq, &lambda, closest_ss))
{
if (!knife_snap_edge_constrained(kcd, mval, kfv1_sco, kfv2_sco, &dis_sq, closest_ss)) {
continue;
}
}
else {
closest_to_line_segment_v2(closest_ss, cage_ss, kfv1_sco, kfv2_sco);
dis_sq = len_squared_v2v2(closest_ss, cage_ss);
if (dis_sq < cur_dist_sq) {
lambda = line_point_factor_v2(cage_ss, kfv1_sco, kfv2_sco);
}
else {
closest_ray_to_segment_v3(
ray_origin, ray_normal, kfe->v1->cageco, kfe->v2->cageco, test_cagep);
knife_project_v2(kcd, test_cagep, closest_ss);
dis_sq = len_squared_v2v2(closest_ss, mval);
if (dis_sq >= cur_dist_sq) {
continue;
}
}
/* Now we have 'lambda' calculated (in screen-space). */
knife_interp_v3_v3v3(kcd, test_cagep, kfe->v1->cageco, kfe->v2->cageco, lambda);
if (RV3D_CLIPPING_ENABLED(kcd->vc.v3d, kcd->vc.rv3d)) {
/* Check we're in the view */
if (ED_view3d_clipping_test(kcd->vc.rv3d, test_cagep, false)) {
@@ -3744,11 +3723,16 @@ static void knife_snap_curr(KnifeTool_OpData *kcd, const float2 &mval)
{
knife_pos_data_clear(&kcd->curr);
if (knife_find_closest_face(kcd, mval, &kcd->curr)) {
float3 ray_origin;
float3 ray_normal;
ED_view3d_win_to_ray_clipped(
kcd->vc.depsgraph, kcd->region, kcd->vc.v3d, mval, ray_origin, ray_normal, false);
if (knife_find_closest_face(kcd, ray_origin, ray_normal, mval, &kcd->curr)) {
if (!kcd->ignore_edge_snapping || !kcd->ignore_vert_snapping) {
KnifePosData kpos_tmp = kcd->curr;
if (knife_find_closest_edge_of_face(
kcd, kpos_tmp.ob_index, kpos_tmp.bmface, kpos_tmp.mval, &kpos_tmp))
kcd, kpos_tmp.ob_index, kpos_tmp.bmface, ray_origin, ray_normal, mval, &kpos_tmp))
{
if (!kcd->ignore_edge_snapping) {
kcd->curr = kpos_tmp;