Add "frame" attribute to <attach> element.
The `<attach>` element now supports a "frame" attribute, allowing users to specify either a "body" or a "frame" to attach to, but not both. The XML parser has been updated to handle this new attribute and the mutual exclusivity constraint. PiperOrigin-RevId: 941245904 Change-Id: I4c0edeed5f3a9e456aed96c373b1647fe79841d9
This commit is contained in:
Yuval Tassa
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Copybara-Service
Copybara-Service
parent
1f6cf4035c
commit
c6c3ec3149
+29
-12
@@ -3996,33 +3996,50 @@ Associate this body with an :ref:`engine plugin<exPlugin>`. Either :at:`plugin`
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:el-prefix:`body/` |-| **attach** |*|
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The :el:`attach` element is used to insert a sub-tree of bodies from another model into this model's kinematic tree.
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The :el:`attach` element is used to insert elements from another (child) model into this (parent) model's kinematic tree.
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Unlike :ref:`include<include>`, which is implemented in the parser and is equivalent to copying and pasting XML from one
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file into another, :el:`attach` is implemented in the model compiler. In order to use this element, the sub-model must
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first be defined as an :ref:`asset<asset-model>`. When creating an attachment, the top body of the attached subtree is
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specified, and all referencing elements outside the kinematic tree (e.g., sensors and actuators), are also copied into
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the top-level model. Additionally, any elements referenced from within the attached subtree (e.g. defaults and assets)
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will be copied in to the top-level model. :el:`attach` is a :ref:`meta-element`, so upon saving all attachments will
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first be defined as an :ref:`asset<asset-model>`. When creating an attachment, a frame, body or the entire child model in the
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child model is specified, and all referencing elements outside the kinematic tree (e.g., sensors and actuators), are also copied into
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the parent model. Additionally, any elements referenced from within the attached subtree (e.g. defaults and assets)
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will be copied in to the parent model. :el:`attach` is a :ref:`meta-element`, so upon saving all attachments will
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appear in the saved XML file. Note that this element is a subset of the functionality of the procedural
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:ref:`attachment<meAttachment>` functionality. As such, it shares the same limitations as described there. In addition,
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when the :el:`attach` element is used, it is not possible to attach an entire model (i.e. including all elements,
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referenced or not).
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:ref:`attachment<meAttachment>` functionality. As such, it shares the same limitations as described there. See example `here
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<https://github.com/google-deepmind/mujoco/blob/main/test/xml/testdata/parent.xml>`__.
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.. admonition:: Known issues
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:class: note
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The following known limitations exist, to be addressed in a future release:
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- All assets from the child model will be copied in, whether they are referenced or not.
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- Circular references are not checked for and will lead to infinite loops.
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- When attaching a model with :ref:`keyframes<keyframe>`, model compilation is required for the re-indexing to be
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finalized. If a second attachment is performed without compilation, the keyframes from the first attachment will be
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lost.
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.. _body-attach-model:
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:at:`model`: :at-val:`string, required`
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The sub-model from which to attach a subtree.
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The child model from which to attach a subtree or a frame.
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.. _body-attach-body:
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:at:`body`: :at-val:`string, optional`
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Name of the body in the sub-model to attach here. The body and its subtree will be attached. If this attribute is not
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specified, the contents of the world body will be attached in a new :ref:`frame<body-frame>`.
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Name of the body in the child model to attach here. The body and its subtree will be attached. If neither this
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attribute nor :ref:`frame<body-attach-frame>` is specified (only one allowed), the contents of the world body will
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be attached in a new :ref:`frame<body-frame>`.
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.. _body-attach-frame:
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:at:`frame`: :at-val:`string, optional`
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Name of the frame in the child model to attach here. If neither this attribute nor :ref:`body<body-attach-body>` is
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specified (only one allowed), the contents of the world body will be attached in a new :ref:`frame<body-frame>`.
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.. _body-attach-prefix:
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:at:`prefix`: :at-val:`string, required`
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Prefix to prepend to names of elements in the sub-model. This attribute is required to prevent name collisions with
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Prefix to prepend to names of elements in the child model. This attribute is required to prevent name collisions with
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the parent or when attaching the same sub-tree multiple times.
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Executable → Regular
+3
@@ -983,6 +983,9 @@
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.. grid-item::
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:ref:`body<body-attach-body>`
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.. grid-item::
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:ref:`frame<body-attach-frame>`
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.. grid-item::
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:ref:`prefix<body-attach-prefix>`
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@@ -470,7 +470,7 @@ std::vector<const char*> MJCF[nMJCF] = {
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{"config", "*", "key", "value"},
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{">"},
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{">"},
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{"attach", "*", "model", "body", "prefix"},
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{"attach", "*", "model", "body", "frame", "prefix"},
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{"site", "*", "name", "class", "type", "group", "pos", "quat", "material",
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"size", "fromto", "axisangle", "xyaxes", "zaxis", "euler", "rgba", "user"},
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{"camera", "*", "name", "class", "projection",
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@@ -4170,35 +4170,40 @@ void mjXReader::Body(XMLElement* section, mjsBody* body, mjsFrame* frame,
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// attachment
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else if (name == "attach") {
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string model_name, body_name, prefix;
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string model_name, child_name, prefix;
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ReadAttrTxt(elem, "model", model_name, /*required=*/true);
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ReadAttrTxt(elem, "body", body_name, /*required=*/false);
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bool has_body = ReadAttrTxt(elem, "body", child_name, /*required=*/false);
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bool has_frame = ReadAttrTxt(elem, "frame", child_name, /*required=*/false);
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ReadAttrTxt(elem, "prefix", prefix, /*required=*/true);
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mjsBody* child_body = mjs_findBody(spec, (prefix+body_name).c_str());
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if (has_body && has_frame) {
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throw mjXError(elem, "only one of body or frame can be specified in attach");
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}
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mjtObj type = has_body ? mjOBJ_BODY : mjOBJ_FRAME;
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mjsElement* child = mjs_findElement(spec, type, (prefix+child_name).c_str());
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mjsFrame* pframe = frame ? frame : mjs_addFrame(body, nullptr);
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if (!child_body) {
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if (!child) {
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mjSpec* asset = mjs_findSpec(spec, model_name.c_str());
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if (!asset) {
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throw mjXError(elem, "could not find model '%s'", model_name.c_str());
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}
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mjsElement* child;
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if (body_name.empty()) {
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if (child_name.empty()) {
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child = asset->element;
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} else {
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child_body = mjs_findBody(asset, body_name.c_str());
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if (!child_body) {
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throw mjXError(elem, "could not find body '%s''%s'", body_name.c_str());
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child = mjs_findElement(asset, type, child_name.c_str());
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if (!child) {
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throw mjXError(elem, "could not find %s",
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(string(mju_type2Str(type)) + " '" + child_name + "'").c_str());
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}
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child = child_body->element;
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}
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if (!mjs_attach(pframe->element, child, prefix.c_str(), "")) {
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throw mjXError(elem, "%s", stripError(mjs_getError(spec)));
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}
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} else {
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// only set frame to existing body
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if (mjs_setFrame(child_body->element, pframe)) {
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if (mjs_setFrame(child, pframe)) {
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throw mjXError(elem, "%s", stripError(mjs_getError(spec)));
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}
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}
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Vendored
+12
-1
@@ -1,7 +1,18 @@
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<mujoco model="child">
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<worldbody>
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<body name="body">
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<geom name="geom" size="1" pos="2 0 0"/>
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<geom name="geom" size="1" pos="0 0 -2" rgba="1 0 0 1"/>
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</body>
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<frame name="frame">
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<body name="body2" pos="-1 0 0">
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<freejoint/>
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<geom name="geom2" type="box" size="1 1 1" rgba="0 1 0 1"/>
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</body>
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<body name="body3" pos="1 0 0">
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<freejoint/>
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<geom name="geom3" type="box" size="1 1 1" rgba="0 1 0 1"/>
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</body>
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</frame>
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</worldbody>
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</mujoco>
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Vendored
+16
-2
@@ -3,9 +3,23 @@
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<model name="other" file="child.xml"/>
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</asset>
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<worldbody>
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<!-- attach body to body -->
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<body name="parent">
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<geom name="geom" size="2"/>
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<attach model="other" body="body" prefix="other"/>
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<geom name="geom" size="1" pos="0 0 2"/>
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<attach model="other" body="body" prefix="other1"/>
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</body>
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<!-- attach frame to body (world) -->
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<attach model="other" frame="frame" prefix="other2"/>
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<!-- attach frame to frame -->
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<frame name="top" pos="0 0 4">
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<attach model="other" frame="frame" prefix="other3"/>
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</frame>
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<!-- attach body to frame -->
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<frame name="bottom-right" pos="2 0 -1">
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<attach model="other" body="body" prefix="other4"/>
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</frame>
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</worldbody>
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</mujoco>
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