So for this
week, after getting tloc set up and running I began to look at a couple of
samples. I just wanted to get a camera setup and running with a model so I
looked specifically at the obj loader sample with the arc ball camera. At first
I wasn’t used to the amount of use of inheritance and pointers used in tloc,
but I quickly got used to the entity and component concept because I’ve been
playing around with the Unity game engine all summer and have made some
prototypes using it. I tried changing the positioning and rotation of the
camera however it wasn’t behaving properly so I decided to write my own view
matrix function which returns a 4 by 4 matrix determining where the camera will
look at. This has allowed me to focus the camera on our player object.

math_t::Mat4f GetViewMatrix(const math_t::Vec3f& eye, const
math_t::Vec3f& target)

{

math_t::Vec3f
up = math_t::Vec3f(0.0f, 1.0f, 0.0f);

math_t::Vec3f
zaxis = math_t::Vec3f(eye - target);

zaxis.Normalize();

math_t::Vec3f
up_cross_zaxis;

up_cross_zaxis.Cross(up,
zaxis);

math_t::Vec3f
xaxis = up_cross_zaxis;

xaxis.Normalize();

math_t::Vec3f
zaxis_cross_xaxis;

zaxis_cross_xaxis.Cross(zaxis,
xaxis);

math_t::Vec3f
yaxis = zaxis_cross_xaxis;

float dot_xaxis_eye = xaxis.Dot(eye);

float dot_yaxis_eye = yaxis.Dot(eye);

float dot_zaxis_eye = zaxis.Dot(eye);

math_t::Mat4f
viewMatrix(xaxis[0],yaxis[0],zaxis[0], 0,

xaxis[1],yaxis[1],zaxis[1], 0,

xaxis[2],yaxis[2],zaxis[2], 0,

-dot_xaxis_eye, -dot_yaxis_eye, -dot_zaxis_eye,
1);

return viewMatrix;

}

Next was to
rotate the player box and have the camera follow the rotation and face where
the player is facing. This was simply done by taking in the player’s rotated
angle and calculating the rotation of the camera around the player’s position.

//rorate the entity around the Y axis

void RotateEntity(const
core_cs::entity_vptr a_ent, double angle)

{

math_cs::transform_sptr
transform = a_ent->GetComponent<math_cs::Transform>();

math_cs::Transform::orientation_type
orien(transform->GetOrientation());

//rotating around Y axis test

math_t::Mat3f
RotationMatrix((float)cos(angle), 0, (float)sin(angle),

0, 1, 0,

(float)-sin(angle),
0, (float)cos(angle));

transform->SetOrientation(RotationMatrix);

}

I've also added spring physics to the camera so it adds a bit of a delay following the player.

//camera with spring physics (chase camera) for adding delay while following the player

static math_t::Vec3f camVelo(0);

math_t::Vec3f originalPos = transform->GetPosition();

math_t::Vec3f targetPos = newCamPos;

float stiffness = 0.8f;

float damping = 0.15f;

float mass = 0.005f;

math_t::Vec3f stretch = originalPos - newCamPos;

math_t::Vec3f force = -stiffness * stretch - damping * camVelo;

math_t::Vec3f acceleration = force/mass;

camVelo += acceleration * 0.001f;

newCamPos = originalPos + (camVelo * 0.001f);

newCamPos[1] = targetPos[1];

static math_t::Vec3f camVelo(0);

math_t::Vec3f originalPos = transform->GetPosition();

math_t::Vec3f targetPos = newCamPos;

float stiffness = 0.8f;

float damping = 0.15f;

float mass = 0.005f;

math_t::Vec3f stretch = originalPos - newCamPos;

math_t::Vec3f force = -stiffness * stretch - damping * camVelo;

math_t::Vec3f acceleration = force/mass;

camVelo += acceleration * 0.001f;

newCamPos = originalPos + (camVelo * 0.001f);

newCamPos[1] = targetPos[1];