Added README

README.md

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+# Trajectory Preview
+
+ROS-enabled Qt widget and Rviz panel for interactively previewing robot trajectories
+
+![Trajectory preview panel](docs/panel.png)
+
+## Usage
+The widget subscribes to a `trajectory_msgs/JointTrajectory` definition of a robot trajectory and 
+publishes a `sensor_msgs/JointState` message corresponding to the state in the trajectory at which the slider is set.
+
+An Rviz `RobotModel` display can then be used to visualize the preview using the following pipeline:
+  - The trajectory preview widget publishes joint states (`/trajectory/joint_states`)
+  - A `JointStatePublisher` node integrates the trajectory preview widget joint states topic (`/trajectory/joint_states`) into a constantly published joint states topic (`/preview/joint_states`)
+  - A `RobotStatePublisher` node subscribes to the high-level preview joint states topic (`/preview/joint_states`) and creates a TF tree with the prefix `preview`
+  - The Rviz `RobotModel` display animates the robot model using the `preview`-prefixed TF tree
+
+This pipeline is provided in the `robot_model_preview_pipeline.launch.xml` file
+
+## Build
+```commandLine
+cd <ws>
+rosdep install --from-paths src -iry
+colcon build
+```