Tesseract Scene Graph Package

Background

This package contains the scene graph and parsers. The scene graph is used to manage the connectivity of the environment. The scene graph inherits from boost graph so you are able to leverage boost graph utilities for searching.

Scene Graph (Tree)

Scene Graph (Acyclic)

Features

1. Links - Get, Add, Remove, Modify, Show/Hide, and Enable/Disable Collision
2. Joints - Get, Add, Remove, Move and Modify
3. Allowed Collision Matrix - Get, Add, Remove
4. Graph Functions
   • Get Inbound/Outbound Joints for Link
   • Check if acyclic
   • Check if tree
   • Get Adjacent/InvAdjacent Links for Joint
5. Utility Functions
   • Save to Graph to Graph Description Language (DOT)
   • Get shortest path between two Links
6. Parsers
   • URDF Parser
   • SRDF Parser
   • KDL Parser
   • Mesh Parser

Examples

1. Building A Scene Graph
2. Create Scene Graph from URDF
3. Parse SRDF adding ACM to Scene Graph
4. Parse Mesh

Building A Scene Graph

#include <console_bridge/console.h>
#include <tesseract_scene_graph/graph.h>
#include <iostream>

using namespace tesseract_scene_graph;

std::string toString(const SceneGraph::Path& path)
{
  std::stringstream ss;
  ss << path;
  return ss.str();
}

std::string toString(bool b) { return b ? "true" : "false"; }

int main(int /*argc*/, char** /*argv*/)
{
  console_bridge::setLogLevel(console_bridge::LogLevel::CONSOLE_BRIDGE_LOG_INFO);

  // Create scene graph
  SceneGraph g;

  // Create links
  Link link_1("link_1");
  Link link_2("link_2");
  Link link_3("link_3");
  Link link_4("link_4");
  Link link_5("link_5");

  // Add links
  g.addLink(link_1);
  g.addLink(link_2);
  g.addLink(link_3);
  g.addLink(link_4);
  g.addLink(link_5);

  // Create joints
  Joint joint_1("joint_1");
  joint_1.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_1.parent_link_name = "link_1";
  joint_1.child_link_name = "link_2";
  joint_1.type = JointType::FIXED;

  Joint joint_2("joint_2");
  joint_2.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_2.parent_link_name = "link_2";
  joint_2.child_link_name = "link_3";
  joint_2.type = JointType::PLANAR;

  Joint joint_3("joint_3");
  joint_3.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_3.parent_link_name = "link_3";
  joint_3.child_link_name = "link_4";
  joint_3.type = JointType::FLOATING;

  Joint joint_4("joint_4");
  joint_4.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_4.parent_link_name = "link_2";
  joint_4.child_link_name = "link_5";
  joint_4.type = JointType::REVOLUTE;

  // Add joints
  g.addJoint(joint_1);
  g.addJoint(joint_2);
  g.addJoint(joint_3);
  g.addJoint(joint_4);

  // Check getAdjacentLinkNames Method
  std::vector<std::string> adjacent_links = g.getAdjacentLinkNames("link_3");
  for (const auto& adj : adjacent_links)
    CONSOLE_BRIDGE_logInform(adj.c_str());

  // Check getInvAdjacentLinkNames Method
  std::vector<std::string> inv_adjacent_links = g.getInvAdjacentLinkNames("link_3");
  for (const auto& inv_adj : inv_adjacent_links)
    CONSOLE_BRIDGE_logInform(inv_adj.c_str());

  // Check getLinkChildrenNames
  std::vector<std::string> child_link_names = g.getLinkChildrenNames("link_2");
  for (const auto& child_link : child_link_names)
    CONSOLE_BRIDGE_logInform(child_link.c_str());

  // Check getJointChildrenNames
  child_link_names = g.getJointChildrenNames("joint_1");
  for (const auto& child_link : child_link_names)
    CONSOLE_BRIDGE_logInform(child_link.c_str());

  // Save Graph
  g.saveDOT("/tmp/graph_acyclic_tree_example.dot");

  // Test if the graph is Acyclic
  bool is_acyclic = g.isAcyclic();
  CONSOLE_BRIDGE_logInform(toString(is_acyclic).c_str());

  // Test if the graph is Tree
  bool is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

  // Test for unused links
  Link link_6("link_6");
  g.addLink(link_6);
  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

  // Remove unused link
  g.removeLink(link_6.getName());
  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

  // Add new joint
  Joint joint_5("joint_5");
  joint_5.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_5.parent_link_name = "link_5";
  joint_5.child_link_name = "link_4";
  joint_5.type = JointType::CONTINUOUS;
  g.addJoint(joint_5);

  // Save new graph
  g.saveDOT("/tmp/graph_acyclic_not_tree_example.dot");

  // Test again if the graph is Acyclic
  is_acyclic = g.isAcyclic();
  std::cout << toString(is_acyclic).c_str();

  // Test again if the graph is Tree
  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

  // Get Shortest Path
  SceneGraph::Path path = g.getShortestPath("link_1", "link_4");
  CONSOLE_BRIDGE_logInform(toString(path).c_str());
}

Example Explanation

Create Scene Graph

  SceneGraph g;

Add Links

Create the links. The links are able to be configured see Link documentation.

  Link link_1("link_1");
  Link link_2("link_2");
  Link link_3("link_3");
  Link link_4("link_4");
  Link link_5("link_5");

Add the links to the scene graph

  g.addLink(link_1);
  g.addLink(link_2);
  g.addLink(link_3);
  g.addLink(link_4);
  g.addLink(link_5);

Add Joints

Create the joints. The links are able to be configured see Joint documentation.

  Joint joint_1("joint_1");
  joint_1.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_1.parent_link_name = "link_1";
  joint_1.child_link_name = "link_2";
  joint_1.type = JointType::FIXED;

  Joint joint_2("joint_2");
  joint_2.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_2.parent_link_name = "link_2";
  joint_2.child_link_name = "link_3";
  joint_2.type = JointType::PLANAR;

  Joint joint_3("joint_3");
  joint_3.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_3.parent_link_name = "link_3";
  joint_3.child_link_name = "link_4";
  joint_3.type = JointType::FLOATING;

  Joint joint_4("joint_4");
  joint_4.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_4.parent_link_name = "link_2";
  joint_4.child_link_name = "link_5";
  joint_4.type = JointType::REVOLUTE;

Add the joints to the scene graph_acyclic_tree_example

  g.addJoint(joint_1);
  g.addJoint(joint_2);
  g.addJoint(joint_3);
  g.addJoint(joint_4);

Inspect Scene Graph

Get the adjacent links for link_3 and print to terminal

  std::vector<std::string> adjacent_links = g.getAdjacentLinkNames("link_3");
  for (const auto& adj : adjacent_links)
    CONSOLE_BRIDGE_logInform(adj.c_str());

Get the inverse adjacent links for link_3 and print to terminal

  std::vector<std::string> inv_adjacent_links = g.getInvAdjacentLinkNames("link_3");
  for (const auto& inv_adj : inv_adjacent_links)
    CONSOLE_BRIDGE_logInform(inv_adj.c_str());

Get child link names for link link_3 and print to terminal

  std::vector<std::string> child_link_names = g.getLinkChildrenNames("link_2");
  for (const auto& child_link : child_link_names)
    CONSOLE_BRIDGE_logInform(child_link.c_str());

Get child link names for joint joint_1 and print to terminal

  child_link_names = g.getJointChildrenNames("joint_1");
  for (const auto& child_link : child_link_names)
    CONSOLE_BRIDGE_logInform(child_link.c_str());

Save the graph to a file for visualization

  g.saveDOT("/tmp/graph_acyclic_tree_example.dot");

Test if the graph is Acyclic and print to terminal

  bool is_acyclic = g.isAcyclic();
  CONSOLE_BRIDGE_logInform(toString(is_acyclic).c_str());

Test if the graph is a tree and print to terminal

  bool is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

Detect Unused Links

First add a link but do not create joint and check if it is a tree. It should return false because the link is not associated with a joint.

  Link link_6("link_6");
  g.addLink(link_6);
  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

Remove link and check if it is a tree. It should return true.

  g.removeLink(link_6.getName());
  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

Create Acyclic Graph

Add joint connecting link_5 and link_4 to create an Acyclic graph_acyclic_tree_example

  Joint joint_5("joint_5");
  joint_5.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_5.parent_link_name = "link_5";
  joint_5.child_link_name = "link_4";
  joint_5.type = JointType::CONTINUOUS;
  g.addJoint(joint_5);

Save the Acyclic graph

  g.saveDOT("/tmp/graph_acyclic_not_tree_example.dot");

Test to confirm it is acyclic, should return true.

  is_acyclic = g.isAcyclic();
  std::cout << toString(is_acyclic).c_str();

Test if it is a tree, should return false.

  is_tree = g.isTree();
  CONSOLE_BRIDGE_logInform(toString(is_tree).c_str());

Get Shortest Path

  SceneGraph::Path path = g.getShortestPath("link_1", "link_4");
  CONSOLE_BRIDGE_logInform(toString(path).c_str());

Create Scene Graph from URDF

Example Explanation

Create Resource Locator

Because this is ROS agnostic you need to provide a resource locator for interpreting package:/.

Load URDF

Get the file path to the urdf file

Create scene graph from urdf

Print information about the scene graph to the terminal

Save the graph to a file.

Parse SRDF adding Allowed Collision Matrix to Graph

#include <console_bridge/console.h>
#include <tesseract_scene_graph/graph.h>
#include <tesseract_scene_graph/parser/srdf_parser.h>
#include <tesseract_scene_graph/utils.h>
#include <iostream>

using namespace tesseract_scene_graph;

std::string toString(const SceneGraph::Path& path)
{
  std::stringstream ss;
  ss << path;
  return ss.str();
}

std::string toString(bool b) { return b ? "true" : "false"; }

// Define a resource locator function
std::string locateResource(const std::string& url)
{
  std::string mod_url = url;
  if (url.find("package://tesseract_support") == 0)
  {
    mod_url.erase(0, strlen("package://tesseract_support"));
    size_t pos = mod_url.find("/");
    if (pos == std::string::npos)
    {
      return std::string();
    }

    std::string package = mod_url.substr(0, pos);
    mod_url.erase(0, pos);
    std::string package_path = std::string(TESSERACT_SUPPORT_DIR);

    if (package_path.empty())
    {
      return std::string();
    }

    mod_url = package_path + mod_url;
  }

  return mod_url;
}

int main(int /*argc*/, char** /*argv*/)
{
  std::string srdf_file = std::string(TESSERACT_SUPPORT_DIR) + "/urdf/lbr_iiwa_14_r820.srdf";

  // Create scene graph
  ResourceLocatorFn locator = locateResource;
  SceneGraph g;

  g.setName("kuka_lbr_iiwa_14_r820");

  Link base_link("base_link");
  Link link_1("link_1");
  Link link_2("link_2");
  Link link_3("link_3");
  Link link_4("link_4");
  Link link_5("link_5");
  Link link_6("link_6");
  Link link_7("link_7");
  Link tool0("tool0");

  g.addLink(base_link);
  g.addLink(link_1);
  g.addLink(link_2);
  g.addLink(link_3);
  g.addLink(link_4);
  g.addLink(link_5);
  g.addLink(link_6);
  g.addLink(link_7);
  g.addLink(tool0);

  Joint base_joint("base_joint");
  base_joint.parent_link_name = "base_link";
  base_joint.child_link_name = "link_1";
  base_joint.type = JointType::FIXED;
  g.addJoint(base_joint);

  Joint joint_1("joint_1");
  joint_1.parent_link_name = "link_1";
  joint_1.child_link_name = "link_2";
  joint_1.type = JointType::REVOLUTE;
  g.addJoint(joint_1);

  Joint joint_2("joint_2");
  joint_2.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_2.parent_link_name = "link_2";
  joint_2.child_link_name = "link_3";
  joint_2.type = JointType::REVOLUTE;
  g.addJoint(joint_2);

  Joint joint_3("joint_3");
  joint_3.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_3.parent_link_name = "link_3";
  joint_3.child_link_name = "link_4";
  joint_3.type = JointType::REVOLUTE;
  g.addJoint(joint_3);

  Joint joint_4("joint_4");
  joint_4.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_4.parent_link_name = "link_4";
  joint_4.child_link_name = "link_5";
  joint_4.type = JointType::REVOLUTE;
  g.addJoint(joint_4);

  Joint joint_5("joint_5");
  joint_5.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_5.parent_link_name = "link_5";
  joint_5.child_link_name = "link_6";
  joint_5.type = JointType::REVOLUTE;
  g.addJoint(joint_5);

  Joint joint_6("joint_6");
  joint_6.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_6.parent_link_name = "link_6";
  joint_6.child_link_name = "link_7";
  joint_6.type = JointType::REVOLUTE;
  g.addJoint(joint_6);

  Joint joint_tool0("joint_tool0");
  joint_tool0.parent_link_name = "link_7";
  joint_tool0.child_link_name = "tool0";
  joint_tool0.type = JointType::FIXED;
  g.addJoint(joint_tool0);

  // Parse the srdf
  SRDFModel srdf;
  bool success = srdf.initFile(g, srdf_file);
  CONSOLE_BRIDGE_logInform("SRDF loaded: %s", toString(success).c_str());

  processSRDFAllowedCollisions(g, srdf);

  AllowedCollisionMatrix::ConstPtr acm = g.getAllowedCollisionMatrix();
  const AllowedCollisionMatrix::AllowedCollisionEntries& acm_entries = acm->getAllAllowedCollisions();
  CONSOLE_BRIDGE_logInform("ACM Number of entries: %d", acm_entries.size());
}

Example Explanation

Create Resource Locator

Because this is ROS agnostic you need to provide a resource locator for interpreting package:/.

std::string locateResource(const std::string& url)
{
  std::string mod_url = url;
  if (url.find("package://tesseract_support") == 0)
  {
    mod_url.erase(0, strlen("package://tesseract_support"));
    size_t pos = mod_url.find("/");
    if (pos == std::string::npos)
    {
      return std::string();
    }

    std::string package = mod_url.substr(0, pos);
    mod_url.erase(0, pos);
    std::string package_path = std::string(TESSERACT_SUPPORT_DIR);

    if (package_path.empty())
    {
      return std::string();
    }

    mod_url = package_path + mod_url;
  }

  return mod_url;
}

Load URDF and SRDF

Get the file path to the URDF and SRDF file

Create Scene Graph from URDF

  ResourceLocatorFn locator = locateResource;
  SceneGraph g;

  g.setName("kuka_lbr_iiwa_14_r820");

  Link base_link("base_link");
  Link link_1("link_1");
  Link link_2("link_2");
  Link link_3("link_3");
  Link link_4("link_4");
  Link link_5("link_5");
  Link link_6("link_6");
  Link link_7("link_7");
  Link tool0("tool0");

  g.addLink(base_link);
  g.addLink(link_1);
  g.addLink(link_2);
  g.addLink(link_3);
  g.addLink(link_4);
  g.addLink(link_5);
  g.addLink(link_6);
  g.addLink(link_7);
  g.addLink(tool0);

  Joint base_joint("base_joint");
  base_joint.parent_link_name = "base_link";
  base_joint.child_link_name = "link_1";
  base_joint.type = JointType::FIXED;
  g.addJoint(base_joint);

  Joint joint_1("joint_1");
  joint_1.parent_link_name = "link_1";
  joint_1.child_link_name = "link_2";
  joint_1.type = JointType::REVOLUTE;
  g.addJoint(joint_1);

  Joint joint_2("joint_2");
  joint_2.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_2.parent_link_name = "link_2";
  joint_2.child_link_name = "link_3";
  joint_2.type = JointType::REVOLUTE;
  g.addJoint(joint_2);

  Joint joint_3("joint_3");
  joint_3.parent_to_joint_origin_transform.translation()(0) = 1.25;
  joint_3.parent_link_name = "link_3";
  joint_3.child_link_name = "link_4";
  joint_3.type = JointType::REVOLUTE;
  g.addJoint(joint_3);

  Joint joint_4("joint_4");
  joint_4.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_4.parent_link_name = "link_4";
  joint_4.child_link_name = "link_5";
  joint_4.type = JointType::REVOLUTE;
  g.addJoint(joint_4);

  Joint joint_5("joint_5");
  joint_5.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_5.parent_link_name = "link_5";
  joint_5.child_link_name = "link_6";
  joint_5.type = JointType::REVOLUTE;
  g.addJoint(joint_5);

  Joint joint_6("joint_6");
  joint_6.parent_to_joint_origin_transform.translation()(1) = 1.25;
  joint_6.parent_link_name = "link_6";
  joint_6.child_link_name = "link_7";
  joint_6.type = JointType::REVOLUTE;
  g.addJoint(joint_6);

  Joint joint_tool0("joint_tool0");
  joint_tool0.parent_link_name = "link_7";
  joint_tool0.child_link_name = "tool0";
  joint_tool0.type = JointType::FIXED;
  g.addJoint(joint_tool0);

Parse SRDF

Add Allowed Collision Matrix to Scene Graph

Methods for getting Allowed Collision Matrix from Scene Graph

Parse Mesh from file

Example Explanation

Parse Mesh from File

Mesh files can contain multiple meshes. This is a critical difference between MoveIt which merges all shapes in to a single triangle list for collision checking. By keeping each mesh independent, each will have its own bounding box and if you want to convert to a convex hull you will get a closer representation of the geometry.

Print Mesh Information to Terminal