Objectives

• Incorporate force generators into the physics model

Setup

• Create a new project called lab10_physics, it should be a clone of lab10_lighting project. You can use this one here if you didnt complete it:

• lab10_lighting.zip

Geometry

• Currently Geometry retains a reference to the special 'group' object, extracted from the OBJ file:

struct Geometry : public Renderable
{
 //...
  VertexGroup *vertexGroup;
  std::vector<Vector3> vertices;
  //...
};

• This currently holds a reference to this vertex group. We would like to have our own copy of these vertices - available exclusively to the geometry object under construction. To provide for this, declare a new vector alongside the vertexGroup:

struct Geometry : public Renderable
{
 //...
  VertexGroup *vertexGroup;
  std::vector<Vector3> vertices;
  //...
  void extractVertices();
};

• Also introduce a method to extract the vertices from the group and populate the 'vertices' object (shown above).

• This is the implementation of extractVertices here:

void Geometry::extractVertices()
{
  int newIndex=0;
  foreach (Face &face, faces)
  {
    vector<int> groupIndices = face.vertexIndices;
    face.vertexIndices.clear();
    foreach (int index, groupIndices)
    {
      Vector3 vertex(vertexGroup->vertices[index-1].X, vertexGroup->vertices[index-1].Y, vertexGroup->vertices[index-1].Z);
      vertices.push_back(vertex);
      face.vertexIndices.push_back(newIndex);
      newIndex++;
    }
  }

• Have a close look at this code - essentially it is just replicating that part of the vertexGroup the is used by this Geometry object, and holding it as part of this object.

• We can call this then from the Geometry constructor:

Geometry::Geometry(string groupName, istream& is, VertexGroup*group)
: name(groupName), vertexGroup(group)
{
  //...
  extractVertices();
}

• We can now also change Geometry::render() to use this vector instead of the vertexGroup:

void Geometry::render()
{
  foreach (Face &face, faces)
  {
    face.render(vertices);
  }
}

Face

• Finally, we need to fix an anomaly in face. Currently it looks like this:

void Face::render(std::vector <Vector3>&amp;vertexTable)
{
  vertexIndices.size() == 3?
     glBegin(GL_TRIANGLES)
    :glBegin(GL_QUADS);

  foreach (int index, vertexIndices)
  {
    glVertex3f( vertexTable[index-1].X,
                vertexTable[index-1].Y,
                vertexTable[index-1].Z );
  }
  glEnd();
}

• Note that we have to subtract 1 form the index values, as the Waverfront indices are 1 based.

• We change remove this substraction:

void Face::render(std::vector <Vector3>&amp;vertexTable)
{
  vertexIndices.size() == 3?
     glBegin(GL_TRIANGLES)
    :glBegin(GL_QUADS);

  foreach (int index, vertexIndices)
  {
    glVertex3f( vertexTable[index].X,
                vertexTable[index].Y,
                vertexTable[index].Z );
  }
  glEnd();
}

• Build and test.

utils

• To complete this phase of the physics support - we need to replace a number of classes in the utils folder with these versions:

• vector3.h

• vector3.cpp

• and also introduce these new classes:

• vector4.h

• vector4.cpp

• matrix3.h

• matrix3.cpp

• matrix4.h

• matrix4.cpp

• quat.h

• quat.cpp

• Build and test

physics

• Replace these classes with the following:

• physicsactor.h

• physicsactor.cpp

• cubeactor.h

• cubeactor.cpp

• And introduce these:

• sphereactor.h

• sphereactor.cpp

• forcegenerators.h

• forcegenerators.cpp

• forcegeneratorregistry.h

• forcegeneratorregistry.cpp

Scene + Model

• This is a revised version of the scene implementation:

• scene.h

• scene.cpp

• Build and test this - and load the following model:

• physicsmodel.obj

• Which is created from this may file here:

• physicsmodel.mb

• This is a complete archive of the project in case you have any difficulties

• lab10_physics.zip

Exercises

Exercise 1

• The grid - currently hard coded into the scene - should really be another custom actor. Write this actor, and have it displayed/hidden based on some keystroke

Exercise 2

• The physics properties for the spheres are hard coded. Move them to a separate simulation data file