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Make flex vert0 rotation-invariant for interpolated flexes.

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The `vert0` array, used for parametric vertex coordinates in flexes, is now computed in the flex's local, unrotated frame when using interpolation. This ensures that the parametric coordinates are independent of the flex's initial orientation. A new test confirms that `flex_vert0` is identical for an unrotated and a rotated flex grid.

PiperOrigin-RevId: 908196464
Change-Id: I47d6bcc2bc5df581479d485480e0e947ec6d3ffd
This commit is contained in:
Alessio Quaglino
2026-04-30 08:40:20 -07:00
committed by Copybara-Service
parent 22ca5fe0df
commit 7d54123303
4 changed files with 126 additions and 17 deletions
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test/user/user_flex_test.cc
+52 -3
View File
@@ -392,9 +392,9 @@ TEST_F(UserFlexTest, TrilinearInterpolation) {
EXPECT_EQ(m1->nflexvert, m2->nflexvert);
for (int i = 0; i < 3*m1->nflexvert; ++i) {
EXPECT_EQ(m1->flex_vert[i], d2->flexvert_xpos[i]);
EXPECT_EQ(m1->flex_vert0[i], m2->flex_vert0[i]);
EXPECT_EQ(d1->flexvert_xpos[i], d2->flexvert_xpos[i]);
EXPECT_NEAR(m1->flex_vert[i], d2->flexvert_xpos[i], 1e-7);
EXPECT_NEAR(m1->flex_vert0[i], m2->flex_vert0[i], 1e-7);
EXPECT_NEAR(d1->flexvert_xpos[i], d2->flexvert_xpos[i], 1e-7);
}
EXPECT_EQ(m1->nM, m2->nM);
@@ -1350,6 +1350,55 @@ TEST_F(UserFlexTest, Dof2d) {
mj_deleteData(d_full);
}
TEST_F(UserFlexTest, Vert0RotationInvariant) {
// unrotated trilinear grid
static constexpr char xml_unrotated[] = R"(
<mujoco>
<worldbody>
<body name="parent">
<flexcomp name="test" type="grid" count="2 2 2" spacing="1 1 1"
dim="3" dof="trilinear">
<contact selfcollide="none" internal="false"/>
</flexcomp>
</body>
</worldbody>
</mujoco>
)";
// same grid rotated 45 degrees around Z via parent body quaternion
static constexpr char xml_rotated[] = R"(
<mujoco>
<worldbody>
<body name="parent" quat="0.9238795 0 0 0.3826834">
<flexcomp name="test" type="grid" count="2 2 2" spacing="1 1 1"
dim="3" dof="trilinear">
<contact selfcollide="none" internal="false"/>
</flexcomp>
</body>
</worldbody>
</mujoco>
)";
std::array<char, 1024> error;
mjModel* m1 = LoadModelFromString(xml_unrotated, error.data(), error.size());
ASSERT_THAT(m1, NotNull()) << error.data();
mjModel* m2 = LoadModelFromString(xml_rotated, error.data(), error.size());
ASSERT_THAT(m2, NotNull()) << error.data();
// same number of vertices
ASSERT_EQ(m1->nflexvert, m2->nflexvert);
// vert0 must be identical regardless of rotation
for (int i = 0; i < 3 * m1->nflexvert; ++i) {
EXPECT_NEAR(m1->flex_vert0[i], m2->flex_vert0[i], 1e-10)
<< "vert0 mismatch at index " << i;
}
mj_deleteModel(m1);
mj_deleteModel(m2);
}
} // namespace
} // namespace mujoco
test/xml/xml_native_writer_test.cc
+4 -1
View File
@@ -1404,7 +1404,10 @@ std::vector<std::string> GetWriteReadTestModels() {
absl::StrContains(xml, "hfield_xml") ||
absl::StrContains(xml, "fromto_convex") ||
absl::StrContains(xml, "cube_skin") ||
absl::StrContains(xml, "cube_3x3x3")) {
absl::StrContains(xml, "cube_3x3x3") ||
// exclude files that fail since we do not save pinned flex nodes
absl::StrContains(xml, "gripper_trilinear") ||
absl::StrContains(xml, "strain")) {
continue;
}
models.push_back(xml);