#include "RendererConfig.h"
#ifdef USE_SOFTWARE_TNL

#include "3d.h"
#include "SoftwareInternal.h"
#include <string.h>

struct InstanceContext
{
	matrix m_viewMatrix;		// matrix
	matrix m_unscaledMatrix;	// unscaled matrix
	vector m_viewPosition;		// position
	float  m_modelView[4][4];	// model/view transform
};

#define MAX_INSTANCE_DEPTH	30
static InstanceContext gInstanceStack[MAX_INSTANCE_DEPTH];
static int gInstanceDepth = 0;

//instance at specified point with specified orientation
void g3_StartInstanceMatrix( vector *pos, matrix *orient )
{
	ASSERT( orient != NULL );
	ASSERT( gInstanceDepth < MAX_INSTANCE_DEPTH );

	gInstanceStack[gInstanceDepth].m_viewMatrix     = View_matrix;
	gInstanceStack[gInstanceDepth].m_viewPosition   = View_position;
	gInstanceStack[gInstanceDepth].m_unscaledMatrix = Unscaled_matrix;
	memcpy( gInstanceStack[gInstanceDepth].m_modelView, gTransformModelView, sizeof(gTransformModelView) );
	++gInstanceDepth;

	//step 1: subtract object position from view position
	vector tempv = View_position - *pos;

	//step 2: rotate view vector through object matrix
	View_position = tempv * *orient;

	//step 3: rotate object matrix through view_matrix (vm = ob * vm)
	matrix tempm, tempm2 = ~*orient;

	tempm = tempm2 * View_matrix;
	View_matrix = tempm;

	tempm = tempm2 * Unscaled_matrix;
	Unscaled_matrix = tempm;

	// transform the model/view matrix
	g3_GetModelViewMatrix( &View_position, &Unscaled_matrix, (float*)gTransformModelView );
	g3_UpdateFullTransform();
}


//instance at specified point with specified orientation
void g3_StartInstanceAngles(vector *pos,angvec *angles)
{
	if( angles == NULL )
	{
		matrix ident;
		vm_MakeIdentity( &ident );
		g3_StartInstanceMatrix( pos, &ident );
		return;
	}

	matrix tm;
	vm_AnglesToMatrix( &tm, angles->p, angles->h, angles->b );

	g3_StartInstanceMatrix( pos, &tm );
}


//pops the old context
void g3_DoneInstance()
{
	--gInstanceDepth;
	ASSERT( gInstanceDepth >= 0 );

	View_position   = gInstanceStack[gInstanceDepth].m_viewPosition;
	View_matrix     = gInstanceStack[gInstanceDepth].m_viewMatrix;
	Unscaled_matrix = gInstanceStack[gInstanceDepth].m_unscaledMatrix;
	memcpy( gTransformModelView, gInstanceStack[gInstanceDepth].m_modelView, sizeof(gTransformModelView) );
	g3_UpdateFullTransform();
}

#endif