camera.cpp

用opengl实现的bsp管理3D场景的算法

//***********************************************************************//
//																		 //
//		- "Talk to me like I'm a 3 year old!" Programming Lessons -		 //
//                                                                       //
//		$Author:		DigiBen		[e-mail]			 //
//																		 //
//		$Program:		BSP Loader 6									 //
//																		 //
//		$Description:	This adds gravity, jumping and walking up steps	 //
//																		 //
//		$Date:			9/30/04											 //
//																		 //
//***********************************************************************//

#include "main.h"
#include "Camera.h"
#include "Quake3Bsp.h"


/////// * /////////// * /////////// * NEW * /////// * /////////// * /////////// *

// In our CheckForMovement() function we add some code to add gravity and velocity
// to our camera.  We also get rid of the ability to move along the Y-Axis by the
// view vector.  That way we just go up only if we jump or go up some stairs/slopes.
// 
//

// Since we need the velocity vector for our camera, let's extern this here
extern CVector3 g_vVelocity;

// Changed the speed from 300 because of the frame interval change in CalculateFrameRate()
#define kSpeed	200.0f		

/////// * /////////// * /////////// * NEW * /////// * /////////// * /////////// *


// Our global float that stores the elapsed time between the current and last frame
double g_FrameInterval = 0.0f;

// Extern the level object so we can call collision detection calls
extern CQuake3BSP g_Level;


///////////////////////////////// CALCULATE FRAME RATE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function calculates the frame rate and time intervals between frames
/////
///////////////////////////////// CALCULATE FRAME RATE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CalculateFrameRate()
{
	static double framesPerSecond   = 0.0f;		// This will store our fps
    static double lastTime			= 0.0f;		// This will hold the time from the last frame
	static char strFrameRate[50] = {0};			// We will store the string here for the window title

	static double frameTime = 0.0f;				// This stores the last frame's time

	// Get the current time in seconds
    double currentTime = timeGetTime() * 0.001f;				


/////// * /////////// * /////////// * NEW * /////// * /////////// * /////////// *

	// We added a small value to the frame interval to account for some video
	// cards (Radeon's) with fast computers falling through the floor without it.

	// Here we store the elapsed time between the current and last frame,
	// then keep the current frame in our static variable for the next frame.
 	g_FrameInterval = currentTime - frameTime + 0.005f;

/////// * /////////// * /////////// * NEW * /////// * /////////// * /////////// *


	frameTime = currentTime;

	// Increase the frame counter
    ++framesPerSecond;

	// Now we want to subtract the current time by the last time that was stored
	// to see if the time elapsed has been over a second, which means we found our FPS.
    if( currentTime - lastTime > 1.0f )
    {
		// Here we set the lastTime to the currentTime
	    lastTime = currentTime;
		
		// Copy the frames per second into a string to display in the window title bar
		sprintf(strFrameRate, "Current Frames Per Second: %d", int(framesPerSecond));

		// Set the window title bar to our string
		SetWindowText(g_hWnd, strFrameRate);

		// Reset the frames per second
        framesPerSecond = 0;
    }
}


/////////////////////////////////////// CROSS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This returns a perpendicular vector from 2 given vectors by taking the cross product.
/////
/////////////////////////////////////// CROSS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
												
CVector3 Cross(CVector3 vVector1, CVector3 vVector2)
{
	CVector3 vNormal;	

	// Calculate the cross product with the non communitive equation
	vNormal.x = ((vVector1.y * vVector2.z) - (vVector1.z * vVector2.y));
	vNormal.y = ((vVector1.z * vVector2.x) - (vVector1.x * vVector2.z));
	vNormal.z = ((vVector1.x * vVector2.y) - (vVector1.y * vVector2.x));

	// Return the cross product
	return vNormal;										 
}


/////////////////////////////////////// MAGNITUDE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This returns the magnitude of a vector
/////
/////////////////////////////////////// MAGNITUDE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

float Magnitude(CVector3 vNormal)
{
	// Here is the equation:  magnitude = sqrt(V.x^2 + V.y^2 + V.z^2) : Where V is the vector
	return (float)sqrt( (vNormal.x * vNormal.x) + 
						(vNormal.y * vNormal.y) + 
						(vNormal.z * vNormal.z) );
}


/////////////////////////////////////// NORMALIZE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This returns a normalize vector (A vector exactly of length 1)
/////
/////////////////////////////////////// NORMALIZE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

CVector3 Normalize(CVector3 vVector)
{
	// Get the magnitude of our normal
	float magnitude = Magnitude(vVector);				

	// Now that we have the magnitude, we can divide our vector by that magnitude.
	// That will make our vector a total length of 1.  
	vVector = vVector / magnitude;		
	
	// Finally, return our normalized vector
	return vVector;										
}


///////////////////////////////// CCAMERA \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This is the class constructor
/////
///////////////////////////////// CCAMERA \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

CCamera::CCamera()
{
	CVector3 vZero = CVector3(0.0, 0.0, 0.0);		// Init a vVector to 0 0 0 for our position
	CVector3 vView = CVector3(0.0, 1.0, 0.5);		// Init a starting view vVector (looking up and out the screen) 
	CVector3 vUp   = CVector3(0.0, 0.0, 1.0);		// Init a standard up vVector (Rarely ever changes)

	m_vPosition	= vZero;					// Init the position to zero
	m_vView		= vView;					// Init the view to a std starting view
	m_vUpVector	= vUp;						// Init the UpVector
}


///////////////////////////////// POSITION CAMERA \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function sets the camera's position and view and up vVector.
/////
///////////////////////////////// POSITION CAMERA \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CCamera::PositionCamera(float positionX, float positionY, float positionZ,
				  		     float viewX,     float viewY,     float viewZ,
							 float upVectorX, float upVectorY, float upVectorZ)
{
	CVector3 vPosition	= CVector3(positionX, positionY, positionZ);
	CVector3 vView		= CVector3(viewX, viewY, viewZ);
	CVector3 vUpVector	= CVector3(upVectorX, upVectorY, upVectorZ);

	// The code above just makes it cleaner to set the variables.
	// Otherwise we would have to set each variable x y and z.

	m_vPosition = vPosition;					// Assign the position
	m_vView     = vView;						// Assign the view
	m_vUpVector = vUpVector;					// Assign the up vector
}


///////////////////////////////// SET VIEW BY MOUSE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This allows us to look around using the mouse, like in most first person games.
/////
///////////////////////////////// SET VIEW BY MOUSE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CCamera::SetViewByMouse()
{
	POINT mousePos;									// This is a window structure that holds an X and Y
	int middleX = SCREEN_WIDTH  >> 1;				// This is a binary shift to get half the width
	int middleY = SCREEN_HEIGHT >> 1;				// This is a binary shift to get half the height
	float angleY = 0.0f;							// This is the direction for looking up or down
	float angleZ = 0.0f;							// This will be the value we need to rotate around the Y axis (Left and Right)
	static float currentRotX = 0.0f;
	
	// Get the mouse's current X,Y position
	GetCursorPos(&mousePos);						
	
	// If our cursor is still in the middle, we never moved... so don't update the screen
	if( (mousePos.x == middleX) && (mousePos.y == middleY) ) return;

	// Set the mouse position to the middle of our window
	SetCursorPos(middleX, middleY);							

	// Get the direction the mouse moved in, but bring the number down to a reasonable amount
	angleY = (float)( (middleX - mousePos.x) ) / 500.0f;		
	angleZ = (float)( (middleY - mousePos.y) ) / 500.0f;		

	// Here we keep track of the current rotation (for up and down) so that
	// we can restrict the camera from doing a full 360 loop.
	currentRotX -= angleZ;  

	// To find the axis we need to rotate around for up and down
	// movements, we need to get a perpendicular vector from the
	// camera's view vector and up vector.  This will be the axis.
	CVector3 vAxis = Cross(m_vView - m_vPosition, m_vUpVector);
	vAxis = Normalize(vAxis);

	// Rotate around our perpendicular axis and along the y-axis
	RotateView(angleZ, vAxis.x, vAxis.y, vAxis.z);
	RotateView(angleY, 0, 1, 0);
}


///////////////////////////////// ROTATE VIEW \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This rotates the view around the position using an axis-angle rotation
/////
///////////////////////////////// ROTATE VIEW \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CCamera::RotateView(float angle, float x, float y, float z)
{