Create Ground

[jaeyoung]

Ground

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Ground is one system. This has one link and one collision geometry basically.
Let's make a ground system class.

• Declare ground class inheriting srSystem.
      class Ground: public srSystem
  
• Declare one srLink and one srCollision for ground.
      public:
          srLink*      m_Ground;
          srCollision* m_Plane;
  
• Declare constructor and destructor.
      public:
           Ground();
          ~Ground();
  
• Declare a ground creating function, which returns a srSystem pointer.
      srSystem* BuildGround();
  
• Define constructor and destructor.
      Ground::Ground()
      {
          m_Ground = new srLink;
          m_Plane = new srCollision;
      }
  
      Ground::~Ground()
      {
          delete m_Ground;
          delete m_Plane;
      }
  
• Define BuildGround function.
  First, set m_Ground properties.
          m_Ground->GetGeomInfo().SetShape(srGeometry::PLANE);
          m_Ground->UpdateInertia();
  Every class derived from srEntity has a srGeometry member variable. Call srEntity::GetGeomInfo() function in order to get information about shape, color, dimension, etc.
  After setting the shape of srLink, you must call UpdateInertia(density) function. This function updates the mass and inertia of a link. The argument is density of a link. In case of a fixed link such as ground, since it is not important whether the mass and inertia values are exact, the density does not matter. (Default value is 1000 kg/m^3.)
  
  Next, set collision properties.
          m_Plane->GetGeomInfo().SetShape(srGeometryInfo::PLANE);
          m_Plane->SetLocalFrame(SE3());
  Make m_Plane have the same shape as m_Ground.
  SetLocalFrame() function sets the relative orientation and position of the center of srCollision with respect to the center of srLink to be connected with srCollision. (See this post http://r-station.co.kr/forum/viewtopic.php?f=7&t=13&start=0.)
  The argument SE3() makes the center of m_Plane identical to that of m_Ground.
  
  Add m_Plane to m_Ground.
          m_Ground->AddCollision(m_Plane);
  
  Finally, set srSystem properties.
          this->SetBaseLink(m_Ground);
          this->SetBaseLinkType(FIXED);
  Enroll m_Ground into Ground.
  Notify Ground that the base link is not moving.
  

How to use:
    srSpace gSpace;
    Ground gGround;
    gSpace.AddSystem(gGround.BuildGround());

Entire code is below.

header file: Ground.h

Code: Select all

#ifndef EXAMPLE_GROUND
#define EXAMPLE_GROUND

#include "srDyn/srSpace.h"

class Ground: public srSystem
{
public:
    srLink*      m_Ground;
    srCollision* m_Plane;

public:
              Ground();
             ~Ground();
    srSystem* BuildGround();
};
#endif //EXAMPLE_GROUND



source file: Ground.cpp

Code: Select all

#include "Ground.h"

Ground::Ground()
{
    m_Ground = new srLink;
    m_Plane = new srCollision;
}

Ground::~Ground()
{
    delete m_Ground;
    delete m_Plane;
}

srSystem* Ground::BuildGround()
{
    m_Ground->GetGeomInfo().SetShape(srGeometryInfo::PLANE);
    m_Ground->UpdateInertia();

    m_Plane->GetGeomInfo().SetShape(srGeometryInfo::PLANE);
    m_Plane->SetLocalFrame(SE3());

    m_Ground->AddCollision(m_Plane);

    this->SetBaseLink(m_Ground);
    this->SetBaseLinkType(FIXED);

    return this;
}