// gutamatics projection data caching and other functions from SWWM GZ

Struct dt_ProjectionData
{
	dt_GM_Matrix wtc;
	int viewx, viewy, vieww, viewh;
}

Class dt_Utility
{
	// gutamatics caching
	static clearscope void PrepareProjData( out dt_ProjectionData d, Vector3 viewpos, double angle, double pitch, double roll, double fov )
	{
		double aspect = Screen.GetAspectRatio();
		// vertical fov
		double fovratio = (aspect>=1.3)?1.333333:aspect;
		double fovy = 2.*atan(tan(clamp(fov,5,170)/2.)/fovratio);
		// world→clip matrix
		dt_GM_Matrix view = dt_GM_Matrix.view(viewpos,angle,pitch,roll);
		dt_GM_Matrix perp = dt_GM_Matrix.perspective(fovy,aspect,5,65535);
		d.wtc = perp.multiplyMatrix(view);
		// screen coord data
		int sblocks = CVar.FindCVar('screenblocks').GetInt();
		int viewx, viewy, vieww, viewh;
		[viewx, viewy, vieww, viewh] = Screen.GetViewWindow();
		int sh = Screen.GetHeight();
		int h = sh;
		if ( sblocks < 10 ) h = (sblocks*sh/10)&~7;
		int bottom = sh-(h+viewy-((h-viewh)/2));
		d.viewx = viewx;
		d.viewy = sh-bottom-h;
		d.vieww = vieww;
		d.viewh = h;
	}

	static clearscope Vector3 ProjectPoint( dt_ProjectionData d, Vector3 worldpos )
	{
		return d.wtc.multiplyVector3(worldpos).asVector3();
	}

	static clearscope Vector2 NDCToViewport( dt_ProjectionData d, Vector3 ndc )
	{
		return (d.viewx,d.viewy)+(((ndc.x+1)*d.vieww)/2,((-ndc.y+1)*d.viewh)/2);
	}

	// checks if a point is inside the viewport
	static clearscope bool TestScreenBounds( dt_ProjectionData d, Vector2 vpos )
	{
		return ((vpos.x == clamp(vpos.x,d.viewx,d.viewx+d.vieww))
			&& (vpos.y == clamp(vpos.y,d.viewy,d.viewy+d.viewh)));
	}

	static clearscope Vector3 Vec3FromAngle( double angle, double pitch )
	{
		return (cos(angle)*cos(pitch),sin(angle)*cos(pitch),-sin(pitch));
	}

	static clearscope Vector3 CircleOffset( Vector3 y, Vector3 z, double angle, double radius )
	{
		return (y*cos(angle)*radius+z*sin(angle)*radius);
	}

	static clearscope Vector3 ConeSpread( Vector3 x, Vector3 y, Vector3 z, double angle, double spread )
	{
		return (x+y*cos(angle)*spread+z*sin(angle)*spread).unit();
	}

	static clearscope Vector3, Vector3, Vector3 GetAxes( double angle, double pitch, double roll )
	{
		Vector3 x = (1,0,0), y = (0,-1,0), z = (0,0,1);
		Quat r = Quat.FromAngles(angle,pitch,roll);
		return r*x, r*y, r*z;
	}
}