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copybara-github
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Fix attach for spatial tendon. Fixes #3119.
PiperOrigin-RevId: 874067521 Change-Id: If8d415278dde2bccf269cc90e8c176e3d7edefa6
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-2
lines changed

3 files changed

+138
-2
lines changed

‎doc/changelog.rst‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,11 @@ MJX
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1111
- Add batch rendering support for MJX-Warp. See the :ref:`MJX-Warp batch rendering<MjxWarpBatchRendering>` section for details.
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Bug fixes
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^^^^^^^^^
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- Fixed a bug where :ref:`mjs_attach` silently dropped spatial tendons with wrapping geometries that had no
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``sidesite`` attribute (:issue:`3119`, reported by :github:user:`tomstewart89`).
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Version 3.5.0 (February 12, 2026)
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---------------------------------

‎src/user/user_objects.cc‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6267,12 +6267,16 @@ void mjCTendon::ResolveReferences(const mjCModel* m) {
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try {
62686268
// look for wrapped element with namespace
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path[i]->name = prefix + pname + suffix;
6270-
path[i]->sidesite = prefix + psidesite + suffix;
6270+
if (!psidesite.empty()) {
6271+
path[i]->sidesite = prefix + psidesite + suffix;
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}
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path[i]->ResolveReferences(m);
62726274
} catch(mjCError) {
62736275
// remove namespace from wrap names
62746276
path[i]->name = pname;
6275-
path[i]->sidesite = psidesite;
6277+
if (!psidesite.empty()) {
6278+
path[i]->sidesite = psidesite;
6279+
}
62766280
path[i]->ResolveReferences(m);
62776281
nfailure++;
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}

‎test/user/user_api_test.cc‎

Lines changed: 127 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1079,6 +1079,133 @@ TEST_F(MujocoTest, AttachSame) {
10791079
mj_deleteModel(m_expected);
10801080
}
10811081

1082+
TEST_F(MujocoTest, AttachSpatialTendonWithoutSidesite) {
1083+
static constexpr char xml_parent[] = R"(
1084+
<mujoco>
1085+
<worldbody>
1086+
<body name="parent_body">
1087+
<geom size="0.1" type="sphere"/>
1088+
</body>
1089+
</worldbody>
1090+
</mujoco>)";
1091+
1092+
static constexpr char xml_child[] = R"(
1093+
<mujoco>
1094+
<worldbody>
1095+
<body name="child_body">
1096+
<geom name="wrap_geom" size="0.05" type="sphere"/>
1097+
<site name="site_A" pos="0 0 0.1"/>
1098+
<site name="site_B" pos="0 0 -0.1"/>
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<site name="side_site" pos="0.05 0 0"/>
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</body>
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</worldbody>
1102+
<tendon>
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<spatial name="tendon_with_sidesite">
1104+
<site site="site_A"/>
1105+
<geom geom="wrap_geom" sidesite="side_site"/>
1106+
<site site="site_B"/>
1107+
</spatial>
1108+
<spatial name="tendon_without_sidesite">
1109+
<site site="site_A"/>
1110+
<geom geom="wrap_geom"/>
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<site site="site_B"/>
1112+
</spatial>
1113+
</tendon>
1114+
</mujoco>)";
1115+
1116+
std::array<char, 1000> er;
1117+
mjSpec* parent = mj_parseXMLString(xml_parent, 0, er.data(), er.size());
1118+
ASSERT_THAT(parent, NotNull()) << er.data();
1119+
mjSpec* child = mj_parseXMLString(xml_child, 0, er.data(), er.size());
1120+
ASSERT_THAT(child, NotNull()) << er.data();
1121+
1122+
mjsBody* parent_body = mjs_findBody(parent, "parent_body");
1123+
ASSERT_THAT(parent_body, NotNull());
1124+
mjsSite* attach_site = mjs_addSite(parent_body, 0);
1125+
mjs_setName(attach_site->element, "attach_site");
1126+
1127+
mjs_attach(attach_site->element,
1128+
mjs_findBody(child, "child_body")->element, "", "_child");
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1130+
EXPECT_THAT(mjs_findElement(parent, mjOBJ_TENDON,
1131+
"tendon_with_sidesite_child"), NotNull());
1132+
EXPECT_THAT(mjs_findElement(parent, mjOBJ_TENDON,
1133+
"tendon_without_sidesite_child"), NotNull());
1134+
1135+
mjModel* model = mj_compile(parent, nullptr);
1136+
ASSERT_THAT(model, NotNull()) << mjs_getError(parent);
1137+
EXPECT_EQ(model->ntendon, 2);
1138+
1139+
mj_deleteModel(model);
1140+
mj_deleteSpec(parent);
1141+
mj_deleteSpec(child);
1142+
}
1143+
1144+
TEST_F(MujocoTest, AttachSpatialTendonGitHubIssue3119) {
1145+
static constexpr char parent_xml[] = R"(
1146+
<mujoco>
1147+
<worldbody>
1148+
<body name="parent_body">
1149+
<geom size="0.1" type="sphere"/>
1150+
</body>
1151+
</worldbody>
1152+
</mujoco>)";
1153+
1154+
static constexpr char child_xml[] = R"(
1155+
<mujoco>
1156+
<worldbody>
1157+
<body name="child_body">
1158+
<geom name="wrap_geom" size="0.05" type="sphere"/>
1159+
<site name="site_A" pos="0 0 0.1"/>
1160+
<site name="site_B" pos="0 0 -0.1"/>
1161+
<site name="side_site" pos="0.05 0 0"/>
1162+
</body>
1163+
</worldbody>
1164+
<tendon>
1165+
<spatial name="tendon_with_sidesite">
1166+
<site site="site_A"/>
1167+
<geom geom="wrap_geom" sidesite="side_site"/>
1168+
<site site="site_B"/>
1169+
</spatial>
1170+
<spatial name="tendon_without_sidesite">
1171+
<site site="site_A"/>
1172+
<geom geom="wrap_geom"/>
1173+
<site site="site_B"/>
1174+
</spatial>
1175+
</tendon>
1176+
</mujoco>)";
1177+
1178+
std::array<char, 1000> er;
1179+
mjSpec* parent_spec =
1180+
mj_parseXMLString(parent_xml, 0, er.data(), er.size());
1181+
ASSERT_THAT(parent_spec, NotNull()) << er.data();
1182+
mjSpec* child_spec =
1183+
mj_parseXMLString(child_xml, 0, er.data(), er.size());
1184+
ASSERT_THAT(child_spec, NotNull()) << er.data();
1185+
1186+
mjsBody* parent_body = mjs_findBody(parent_spec, "parent_body");
1187+
ASSERT_THAT(parent_body, NotNull());
1188+
mjsSite* attach_site = mjs_addSite(parent_body, 0);
1189+
mjs_setName(attach_site->element, "attach_site");
1190+
1191+
mjs_attach(attach_site->element,
1192+
mjs_findBody(child_spec, "child_body")->element,
1193+
"", "_child");
1194+
1195+
EXPECT_THAT(mjs_findElement(parent_spec, mjOBJ_TENDON,
1196+
"tendon_with_sidesite_child"), NotNull());
1197+
EXPECT_THAT(mjs_findElement(parent_spec, mjOBJ_TENDON,
1198+
"tendon_without_sidesite_child"), NotNull());
1199+
1200+
mjModel* model = mj_compile(parent_spec, nullptr);
1201+
ASSERT_THAT(model, NotNull()) << mjs_getError(parent_spec);
1202+
EXPECT_EQ(model->ntendon, 2);
1203+
1204+
mj_deleteModel(model);
1205+
mj_deleteSpec(parent_spec);
1206+
mj_deleteSpec(child_spec);
1207+
}
1208+
10821209
TEST_F(MujocoTest, AttachDifferent) {
10831210
std::array<char, 1000> er;
10841211
mjtNum tol = 0;

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