#include "camera.h"

/*
The constructor will set the matrix to identity, except the inverted z-axis.
I cant get used to "forward" being negative, but if this bothers you feel free
to change the marked parts.

Also, if you dont like to access the vectors like float-arrays you can always
use vector-pointers, as long as they only contain three floats like this:
struct vector{float x,y,z;};
and replace the float* with vector* in the header file.
*/
Camera::Camera(float x, float y, float z) {
	memset(Transform, 0, 16*sizeof(float));
	Transform[0] = 1.0f;
	Transform[5] = 1.0f;
	Transform[10] = -1.0f;
	Transform[15] = 1.0f;
	Transform[12] = x; Transform[13] = y; Transform[14] = z;

	Right=&Transform[0];
	Up=&Transform[4];
	Forward=&Transform[8];
	Position=&Transform[12];
}

Camera::~Camera() {}

/*
This one does pretty much the same as gluLookAt, just that it doesnt require
to extract the vectors for gluLookAt and have it rebuild the matrix we already
got.
*/
void Camera::setView() {
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	float viewmatrix[16]={//Remove the three - for non-inverted z-axis
						  Transform[0], Transform[4], -Transform[8], 0,
						  Transform[1], Transform[5], -Transform[9], 0,
						  Transform[2], Transform[6], -Transform[10], 0,

						  -(Transform[0]*Transform[12] +
						  Transform[1]*Transform[13] +
						  Transform[2]*Transform[14]),

						  -(Transform[4]*Transform[12] +
						  Transform[5]*Transform[13] +
						  Transform[6]*Transform[14]),

						  //add a - like above for non-inverted z-axis
						  (Transform[8]*Transform[12] +
						  Transform[9]*Transform[13] +
						  Transform[10]*Transform[14]), 1};
	glLoadMatrixf(viewmatrix);
}

void Camera::moveLoc(float x, float y, float z, float distance) {
	float dx=x*Transform[0] + y*Transform[4] + z*Transform[8];
	float dy=x*Transform[1] + y*Transform[5] + z*Transform[9];
	float dz=x*Transform[2] + y*Transform[6] + z*Transform[10];
	Transform[12] += dx * distance;
	Transform[13] += dy * distance;
	Transform[14] += dz * distance;
}

void Camera::moveGlob(float x, float y, float z, float distance) {
	Transform[12] += x * distance;
	Transform[13] += y * distance;
	Transform[14] += z * distance;
}

/*
Here we let OpenGls (most likely quite optimized) functions do the work.
Note that its transformations already are in local coords.
*/
void Camera::rotateLoc(float deg, float x, float y, float z) {
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadMatrixf(Transform);
	glRotatef(deg, x,y,z);
	glGetFloatv(GL_MODELVIEW_MATRIX, Transform);
	glPopMatrix();
}

/*
We have to invert the rotations to get the global axes in local coords.
Luckily thats just the transposed in this case.
*/
void Camera::rotateGlob(float deg, float x, float y, float z) {
	float dx=x*Transform[0] + y*Transform[1] + z*Transform[2];
	float dy=x*Transform[4] + y*Transform[5] + z*Transform[6];
	float dz=x*Transform[8] + y*Transform[9] + z*Transform[10];
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadMatrixf(Transform);
	glRotatef(deg, dx,dy,dz);
	glGetFloatv(GL_MODELVIEW_MATRIX, Transform);
	glPopMatrix();
}

 

#ifndef CAMERA_H
#define CAMERA_H

/*
All the Win/OpenGL stuff.. 
if youre not using Windows you most likely know what goes here
*/
#ifdef _WIN32
#define  WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <GL/gl.h>
#pragma comment (lib, "opengl32.lib")
#pragma comment (lib, "glu32.lib")
#endif

/*
Usage:
You can access the Right/Up/Forward vectors like a float[3] array,
but cannot write to them, because that would screw up the matrix.
Same goes for Position, except its safe to write to it.

setView() has to be called before you draw anything.
Just call it instead of gluLookAt (which most are using)

move and rotate come in two versions. Loc means the transformation
is in local coords, so rotating around (1,0,0) means youre rotating
around your current Right-vector while Glob would rotate around the
global x-axis.

Most likely you will use Loc for controlling the camera, though Glob
can be usefull if you need to apply physics. Also walking characters
will usually rotate around the global rather than around their local Up,
while flying objects will always use local axes.

If talking about objects when this is a camera confuses you: if you drop
the setView() method you can use this for objects in your world too. Just
rename the class to Object3D or something and derive a camera class from it.
*/
class Camera {
public:
	float const *Right, *Up, *Forward;
	float *Position;
private:
	float Transform[16];

public:
	Camera(float x=0.0f, float y=0.0f, float z=0.0f);
	~Camera();

	void setView();
	void moveLoc(float x, float y, float z, float distance=1);
	void moveGlob(float x, float y, float z, float distance=1);
	void rotateLoc(float deg, float x, float y, float z);
	void rotateGlob(float deg, float x, float y, float z);
};

#endif