Add RViz Marker DisplayTypes Tutorial (#4821)

Signed-off-by: Lewe Christiansen <[email protected]>
Co-authored-by: lewec <[email protected]>

Author: LeweC

source/Tutorials/Intermediate/RViz/Marker-Display-types/Marker-Display-types.rst

@@ -0,0 +1,303 @@
+Marker: Display types
+=====================
+
+**Goal:** This tutorial explains the basic Marker types and how to use them.
+
+**Tutorial level:** Intermediate
+
+**Time:** 15 Minutes
+
+.. contents:: Contents
+   :depth: 2
+   :local:
+
+
+Background
+----------
+The Markers display allows programmatic addition of various primitive shapes to the 3D view by sending a
+`visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ or
+`visualization_msgs/msg/MarkerArray <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/MarkerArray.msg>`_ message.
+
+.. image:: images/marker_overview.png
+
+..
+    This is a comment, the next line will be added to the file once the Markers-Sending-Basic-Shapes-CPP is merged to point to the start of the tutorial series.
+    The :doc:`Marker: Sending Basic Shapes <../Markers-Sending-Basic-Shapes-CPP/Markers-Sending-Basic-Shapes-CPP>` that tutorial begins a series of tutorials on sending markers.
+
+The Marker Message
+------------------
+1 Example Usage (C++)
+^^^^^^^^^^^^^^^^^^^^^
+First we will create a simple publisher node that publishes ``Marker`` messages from the ``visualization_messages`` package to the ``visualization_marker`` topic:
+
+.. code-block:: C++
+
+    auto marker_pub = node->create_publisher<visualization_msgs::msg::Marker>("visualization_marker", 1);
+
+After that it is as simple as filling out a `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_
+message and publishing it:
+
+.. code-block:: C++
+
+    visualization_msgs::msg::Marker marker;
+
+    marker.header.frame_id = "/my_frame";
+    marker.header.stamp = rclcpp::Clock().now();
+
+    marker.ns = "basic_shapes";
+    marker.id = 0;
+
+    marker.type = visualization_msgs::msg::Marker::SPHERE;
+
+    marker.action = visualization_msgs::msg::Marker::ADD;
+
+    marker.pose.position.x = 0;
+    marker.pose.position.y = 0;
+    marker.pose.position.z = 0;
+    marker.pose.orientation.x = 0.0;
+    marker.pose.orientation.y = 0.0;
+    marker.pose.orientation.z = 0.0;
+    marker.pose.orientation.w = 1.0;
+
+    marker.scale.x = 1.0;
+    marker.scale.y = 1.0;
+    marker.scale.z = 1.0;
+
+    marker.color.r = 0.0f;
+    marker.color.g = 1.0f;
+    marker.color.b = 0.0f;
+    marker.color.a = 1.0;   // Don't forget to set the alpha!
+
+    // only if using a MESH_RESOURCE marker type:
+    marker.mesh_resource = "package://pr2_description/meshes/base_v0/base.dae";
+
+    marker.lifetime = rclcpp::Duration::from_nanoseconds(0);
+
+    marker_pub->publish(marker);
+
+There is also a `visualization_msgs/msg/MarkerArray <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/MarkerArray.msg>`_ message, which lets you publish many markers at once.
+
+2 Message Parameters
+^^^^^^^^^^^^^^^^^^^^
+
+The Marker message type is defined in `ROS 2 Common Interfaces <https://github.com/ros2/common_interfaces/tree/{DISTRO}/visualization_msgs/msg>_` package.
+The messages in this package include comments that are helpful in understanding each of the fields in the message.
+
+* ``ns``:
+
+    Namespace for these markers. This plus the id form a unique identifier.
+
+* ``id``:
+
+    Unique id assigned to this marker. It is your responsibility to keep these unique within your namespace.
+
+* ``type``:
+
+    Type of marker (Arrow, Sphere, ...). The available types are specified in the message definition.
+
+* ``action``:
+
+    0 = add/modify, 1 = (deprecated), 2 = delete, 3 = deleteall
+
+* ``pose``:
+
+    Pose marker, specified as x/y/z position and x/y/z/w quaternion orientation.
+
+* ``scale``:
+
+    Scale of the marker. Applied before the position/orientation. A scale of [1, 1, 1] means the object will be 1m by 1m by 1m.
+
+* ``color``:
+
+    Color of the object, specified as r/g/b/a, with values in the range of [0, 1]. The, `a` or alpha value, denotes the opacity of the marker with 1 indicating opaque and 0 indicating completely transparent. The default value is 0, or completely transparent. **You must set the a value of your marker to a non-zero value or it will be transparent by default!**
+
+* ``points``:
+
+    Only used for markers of type ``Points``, ``Line strips``, and ``Line`` / ``Cube`` / ``Sphere`` -lists.
+    It's also used for the Arrow type, if you want to specify the arrow start and end points.
+    This entry represents a list of `geometry_msgs/Point` types for the center or each marker object you would like rendered.
+
+* ``colors``:
+
+    This field is only used for markers that use the points member. This field specifies per-vertex color r/g/b/ color  (no alpha yet) for each entry in `points`.
+
+* ``lifetime``:
+
+    A `duration message value <https://docs.ros.org/en/ros2_packages/{DISTRO}/api/builtin_interfaces/interfaces/msg/Duration.html>`_ used to automatically delete the marker after this period of time.
+    The countdown resets if another marker of the same ``namespace`` / ``id`` is received.
+
+* ``frame_locked``:
+
+    Without the ``frame_locked`` parameter the marker will be placed based on the current transform and will stay there even if the given transform changes later.
+    Setting this parameter tells RViz to retransform the marker to the new current location of the specified frame on every update cycle.
+
+* ``text``:
+
+    The text string used for the ``TEXT_VIEW_FACING`` marker type
+
+* ``mesh_resource``:
+
+    The resource location for the ``MESH_RESOURCE`` marker type. Can be any mesh type supported by RViz (``.stl`` or Ogre ``.mesh`` in 1.0, with the addition of COLLADA in 1.1).
+    The format is the URI-form used by `resource_retriever <https://github.com/ros/resource_retriever/tree/{DISTRO}>`_, including the package:// syntax.
+
+3 Object types
+^^^^^^^^^^^^^^
+
+.. _RVizMarkerObjectTypes:
+
+3.1 Arrow (ARROW=0)
+~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/ArrowMarker.png
+
+The arrow type provides two different ways of specifying where the arrow should begin/end:
+
+* ``Position/Orientation``:
+
+    Pivot point is around the tip of its tail. Identity orientation points it along the +X axis. ``scale.x`` is the arrow length, ``scale.y`` is the arrow width and ``scale.z`` is the arrow height.
+
+* ``Start/End Points``:
+
+    You can also specify a start/end point for the arrow, using the points member. If you put points into the points member, it will assume you want to do things this way.
+
+    * The point at index 0 is assumed to be the start point, and the point at index 1 is assumed to be the end.
+    * ``scale.x`` is the shaft diameter, and ``scale.y`` is the head diameter. If ``scale.z`` is not zero, it specifies the head length.
+
+3.2 Cube (CUBE=1)
+~~~~~~~~~~~~~~~~~
+
+.. image:: images/CubeMarker.png
+
+Pivot point is at the center of the cube.
+
+3.3 Sphere (SPHERE=2)
+~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/SphereMarker.png
+
+Pivot point is at the center of the sphere.
+
+``scale.x`` is diameter in x direction, ``scale.y`` in y direction, ``scale.z`` in z direction.
+By setting these to different values you get an ellipsoid instead of a sphere.
+
+3.4 Cylinder (CYLINDER=3)
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/CylinderMarker.png
+
+Pivot point is at the center of the cylinder.
+
+``scale.x`` is diameter in x direction, ``scale.y`` in y direction, by setting these to different values you get an ellipse instead of a circle.
+Use ``scale.z`` to specify the height.
+
+3.5 Line Strip (LINE_STRIP=4)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/LineStripMarker.png
+
+Line strips use the points member of the `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ message.
+It will draw a line between every two consecutive points, so 0-1, 1-2, 2-3, 3-4, 4-5...
+
+Line strips also have some special handling for scale: only ``scale.x`` is used and it controls the width of the line segments.
+
+Note that ``pose`` is still used (the points in the line will be transformed by them), and the lines will be correct relative to the ``frame id`` specified in the header.
+
+3.6 Line List (LINE_LIST=5)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/LineListMarker.png
+
+Line lists use the points member of the `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ message. It will draw a line between each pair of points, so 0-1, 2-3, 4-5, ...
+
+Line lists also have some special handling for scale: only ``scale.x`` is used and it controls the width of the line segments.
+
+Note that ``pose`` is still used (the points in the line will be transformed by them), and the lines will be correct relative to the ``frame id`` specified in the header.
+
+3.7 Cube List (CUBE_LIST=6)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/CubeListMarker.png
+
+A cube list is a list of cubes with all the same properties except their positions.
+Using this object type instead of a `visualization_msgs/msg/MarkerArray <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/MarkerArray.msg>`_ allows RViz to batch-up rendering,
+which causes them to render much faster.
+The caveat is that they all must have the same scale.
+
+The ``points`` member of the `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ message is used for the position of each cube.
+
+3.8 Sphere List (SPHERE_LIST=7)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/SphereListMarker.png
+
+A sphere list is a list of spheres with all the same properties except their positions.
+Using this object type instead of a `visualization_msgs/msg/MarkerArray <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/MarkerArray.msg>`_ allows RViz to batch-up rendering,
+which causes them to render much faster.
+The caveat is that they all must have the same scale.
+
+The ``points`` member of the `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ message is used for the position of each sphere.
+
+Note that ``pose`` is still used (the ``points`` in the line will be transformed by them), and the lines will be correct relative to the ``frame id`` specified in the header.
+
+3.9 Points (POINTS=8)
+~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/PointsMarker.png
+
+Uses the ``points`` member of the `visualization_msgs/msg/Marker <https://github.com/ros2/common_interfaces/blob/{DISTRO}/visualization_msgs/msg/Marker.msg>`_ message.
+
+``Points`` have some special handling for scale: ``scale.x`` is point width, ``scale.y`` is point height
+
+Note that ``pose`` is still used (the ``points`` in the line will be transformed by them), and the lines will be correct relative to the ``frame id`` specified in the header.
+
+3.10 View-Oriented Text (TEXT_VIEW_FACING=9)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/text_view_facing_marker.png
+
+This marker displays text in a 3D spot in the world.
+The text always appears oriented correctly for the RViZ user to see the included text. Uses the ``text`` field in the marker.
+
+Only ``scale.z`` is used. ``scale.z`` specifies the height of an uppercase "A".
+
+3.11 Mesh Resource (MESH_RESOURCE=10)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/mesh_resource_marker.png
+
+Uses the ``mesh_resource`` field in the marker.
+Can be any mesh type supported by RViz (binary ``.stl`` or Ogre ``.mesh`` in 1.0, with the addition of COLLADA (``.dae``) in 1.1).
+The format is the URI-form used by `resource_retriever <https://github.com/ros/resource_retriever/tree/{DISTRO}>`_, including the ``package://`` syntax.
+
+An example of a mesh an its use is:
+
+.. code-block:: C++
+
+    marker.type = visualization_msgs::Marker::MESH_RESOURCE;
+    marker.mesh_resource = "package://pr2_description/meshes/base_v0/base.dae";
+
+Scale on a mesh is relative.
+A scale of (1.0, 1.0, 1.0) means the mesh will display as the exact size specified in the mesh file.
+A scale of (1.0, 1.0, 2.0) means the mesh will show up twice as tall, but the same width/depth.
+
+If the ``mesh_use_embedded_materials`` flag is set to true and the mesh is of a type which supports embedded materials (such as COLLADA),
+the material defined in that file will be used instead of the color defined in the marker.
+
+Since version [1.8], even when ``mesh_use_embedded_materials`` is true,
+if the marker ``color`` is set to anything other than ``r=0``, ``g=0``, ``b=0``, ``a=0`` the marker ``color`` and ``alpha`` will be used to tint the mesh with the embedded material.
+
+3.12 Triangle List (TRIANGLE_LIST=11)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. image:: images/triangle_list_marker.png
+
+Uses the points and optionally colors members.
+Every set of 3 points is treated as a triangle, so indices 0-1-2, 3-4-5, etc.
+
+Note that ``pose`` and ``scale`` are still used (the points in the line will be transformed by them),
+and the lines will be correct relative to the ``frame id`` specified in the header.
+
+4 Rendering Complexity Notes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+A single marker is always less expensive to render than many markers.
+For example, a single cube list can handle thousands of cubes, where we will not be able to render thousands of individual cube markers.