#include ".\impostor.h"

#include <GL/glut.h>
#include <GL/glext.h>
#include <glh/glh_extensions.h>

Impostor::Impostor(void)
{
	m_OwnCamera.setAspectRatio(1);
	m_OwnCamera.SetUpVector(0,1,0);
	NeedRefresh=true;

	m_ErrorTolerance=0.1;
	
	UVs[0]=0;
	UVs[1]=1;
	
	UVs[2]=1;
	UVs[3]=1;
	
	UVs[4]=1;
	UVs[5]=0;

	UVs[6]=0;
	UVs[7]=0;	
}

Impostor::~Impostor(void)
{
}
void Impostor::DisplayScreenQuad(int u,int v)
{
	glDisable(GL_LIGHTING);
	glShadeModel(GL_FLAT);

	//glViewport(0,0,u, v);
    glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();
	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();
		
	glBegin(GL_QUADS);
		
		glTexCoord2f(0,v);
		glVertex3f(-1,1,0);
		
		glTexCoord2f(u,v);
		glVertex3f(1,1,0);
		
		glTexCoord2f(u,0);
		glVertex3f(1,-1,0);
		
		glTexCoord2f(0,0);		
		glVertex3f(-1,-1,0);
		
	glEnd();

	glPopMatrix();
	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();
	
}

void Impostor::Display()
{
	glDisable(GL_LIGHTING);
	glShadeModel(GL_FLAT);

	/*
	glEnableClientState(GL_VERTEX_ARRAY);
	glVertexPointer (3, GL_DOUBLE, 0, Vertices);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
	glTexCoordPointer(2,GL_DOUBLE,0,UVs);
	glDrawArrays(GL_QUADS, 0, 4);*/
	
	glDisableClientState( GL_VERTEX_ARRAY );				
	glDisableClientState( GL_TEXTURE_COORD_ARRAY );				

	
	glBegin(GL_QUADS);

		glTexCoord2dv(&UVs[0]);
		glVertex3dv(&Vertices[0]);
		
		glTexCoord2dv(&UVs[2]);
		glVertex3dv(&Vertices[3]);
		
		glTexCoord2dv(&UVs[4]);
		glVertex3dv(&Vertices[6]);
		
		glTexCoord2dv(&UVs[6]);
		glVertex3dv(&Vertices[9]);
		
	glEnd();
}

void Impostor::updateCamera(bool forceRefresh)
{
	bool needRefresh=false;

	Vector prevViewdir=m_ObjectPosition-m_OwnCamera.getPosition();

	if(prevViewdir.x==0&&prevViewdir.y==0&&prevViewdir.z==0)
	{
			needRefresh=true;			
	}

	if(!forceRefresh&&!needRefresh)
	{
		//compute error 
		double error;		
		
		prevViewdir.Normalize();
		prevViewdir*=m_ObjectBSphereRadius;

		Vector point1=m_ObjectPosition+prevViewdir;
		Vector point2=m_ObjectPosition-prevViewdir;

		Vector v1=point1-m_ViewCamera->getPosition();
		Vector v2=point2-m_ViewCamera->getPosition();

		error=acos((v1*v2)/(v1.Length()*v2.Length()));
		error*=180/M_PI;

		//if error > error tolerance then refresh is needed
		if(error>m_ErrorTolerance)
		{
			needRefresh=true;
		}
	}

	//refresh camera
	if(forceRefresh||needRefresh)
	{
		//to tell the object to refresh the impostor image
		NeedRefresh=true;

		//refresh own camera:position, viewangle, clipplanes
		
		m_OwnCamera.SetPosition(m_ViewCamera->getPosition());
		
		Vector toObject=m_ObjectPosition-m_OwnCamera.getPosition();
		double distance=toObject.Length();
		double nearplane=distance-m_ObjectBSphereRadius;
		double farplane=distance+m_ObjectBSphereRadius;

		double angle=atan(m_ObjectBSphereRadius/distance);

		m_OwnCamera.setFovY(2*angle/M_PI*180);
		m_OwnCamera.setFovX(m_OwnCamera.getFovY());
		m_OwnCamera.setNearClipDistance(nearplane);
		m_OwnCamera.setFarClipDistance(farplane);
		m_OwnCamera.setCorners(-m_ObjectBSphereRadius,m_ObjectBSphereRadius,m_ObjectBSphereRadius,-m_ObjectBSphereRadius);
		
		//if object has moved
		m_OwnCamera.setLookAt(m_ObjectPosition);
		

	}
	else NeedRefresh=false;

	m_UpLeft=m_ViewCamera->getUpVector()-m_ViewCamera->getRightVector();
	m_UpRight=m_ViewCamera->getUpVector()+m_ViewCamera->getRightVector();
	m_DownLeft=m_ViewCamera->getUpVector()*-1-m_ViewCamera->getRightVector();
	m_DownRight=m_ViewCamera->getUpVector()*-1+m_ViewCamera->getRightVector();
	
	
	m_UpLeft.Normalize();
	m_DownLeft.Normalize();
	m_UpRight.Normalize();
	m_DownRight.Normalize();

	double corndist=m_ObjectBSphereRadius*sqrt(2.0);
	m_UpLeft*=corndist;
	m_DownLeft*=corndist;
	m_UpRight*=corndist;
	m_DownRight*=corndist;

	//update corner vertices
	Vertices[9]=m_UpLeft.x;		
	Vertices[10]=m_UpLeft.y;		
	Vertices[11]=m_UpLeft.z;
	
	Vertices[6]=m_UpRight.x;		
	Vertices[7]=m_UpRight.y;		
	Vertices[8]=m_UpRight.z;
	
	Vertices[3]=m_DownRight.x;		
	Vertices[4]=m_DownRight.y;		
	Vertices[5]=m_DownRight.z;
	
	Vertices[0]=m_DownLeft.x;			
	Vertices[1]=m_DownLeft.y;		
	Vertices[2]=m_DownLeft.z; 	

}