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Matrix Yaw and Pitch


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#1 Obi-Dan   Members   -  Reputation: 109

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Posted 07 March 2013 - 07:15 AM

I'm trying to create a first person style camera in OpenGL as part of my coursework. 

This question is more about matricies and vectors so I thought the Math section would be best.

The camera has a 4x4 matrix containing position, rotation etc. also it has a look-at and right vector. (I think I need an up vector too)

 

Currently the camera is able to move forwards in the direction it is facing or strafe from side to side:

 

void moveForward(float distance)
{
	m_lookatVec.x = -sin(m_rotation.y);
	m_lookatVec.y = sin(m_rotation.x);
	m_lookatVec.z = cos(m_rotation.y);
	m_lookatVec.normalise();

	m_position += m_lookatVec * distance;
}

 

This works well when moving down the z axis but the up/down direction seems to flip when travelling up the z axis i.e. when facing upwards the camera moves down on the y axis or up on the y axis when facing downwards.

 

void moveRight(float distance)
{
	m_rightVec.x = cos(m_rotation.y);
	m_rightVec.y = sin(m_rotation.x);
	m_rightVec.z = sin(m_rotation.y);
	m_rightVec.normalise();

	m_position += m_rightVec * distance;
}

 

Not sure if this method is correct, I sort of guessed it but it seems to work!

 

The other issue is with changing the direction of the camera. Rotating around the y axis is easy enough but I would like to be able to change the pitch too. At the moment the Y axis or Yaw is changed like so:

void changeYaw (float degrees)
{
	float rads = MathHelp::degreesToRadians(degrees);
	m_rotation.y += rads;
}

 

 

The rotation vector is later added to a transform matrix with the translation and scale vectors and applied to the camera before rendering.

void Camera::Update()
{
	GUMatrix4 transform, translation, rotation, scale;
	
	GUVector3 rot = getRotation();

	// Create matricies
	translation = GUMatrix4::translationMatrix(getX(), getY(), getZ());
	rotation = GUMatrix4::rotationMatrix(rot.x, rot.y, rot.z);
	scale = GUMatrix4::scaleMatrix(1.0f, 1.0f, 1.0f);

	glMatrixMode(GL_PROJECTION);

	transform  = getProjMat() * scale * rotation * translation;

	glLoadMatrixf((GLfloat*) &transform);

}

 

 

I now need a changePitch method, changeRoll isn't really necessary right now. I'm also guessing the changeYaw method should change to use the up, look and right vectors but I'm not entirely sure how to use them.

 

Any help would be awesome!

Thanks, Dan.

 

 



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