### startOrbit.sml

#####################################################################################
###  For a script to run under TNTsim3D, it must include an instance of
###  class TNTSIM3D named "TNTsim3D".  The script must also be saved as an RVC
###  object in the TNTsim3D Landscape File you want to run it with.
#####################################################################################

# declare class instance for TNTsim3D interface class
class TNTSIM3D TNTsim3D;

class POINT3D viewer, center, orientation;
numeric elev;
numeric roll;
numeric radius;		# radius of orbit
numeric heading;		# heading of viewer in azimuth
numeric direction;	# direction of view in internal cartesian coordinate system

# set fog parameters
class COLOR background;
background.red = 71;
background.green = 90;
background.blue = 100;
TNTsim3D.BackgroundColor = background;
TNTsim3D.UseBackgroundColor = 1;
TNTsim3D.FogType = "ExponentialTwo";
TNTsim3D.FogDensity = 8.00;
TNTsim3D.UseFog = 1;

# set parameters for initial scene (in map coordinates
# of primary terrain); use coordinates appropriate to
# your Landscape File
center.x = 562773;		# initial view center coordinates
center.y = 5116225;
TNTsim3D.GetElevation(center, elev);
center.z = elev;

viewer.x = 563397;		# initial viewer coordinates
viewer.y = 5126070;
TNTsim3D.GetElevation(viewer, elev);
viewer.z = elev + 3380;

# set initial scene using viewer and center positions
TNTsim3D.SetScene(viewer, center, 0);

### compute radius of orbit from current viewer and center positions
radius = sqrt( sqr(viewer.x - center.x) + sqr(viewer.y - center.y) );


#######################################################################
### get viewer position and orientation from current scene to
### get present heading
####################################################################### 
TNTsim3D.GetSceneByOrientation(viewer, orientation);
heading = orientation.z;	# azimuth angle from viewer toward center in degrees
									# clockwise from north

########################################################################
### SML function name predefined in TNTsim3D, called for each frame.
########################################################################
func OnFrame()
	{
	# increment heading
	heading = heading + 0.2;

	# reverse heading and convert to direction angle (counter-clockwise from x axis)
	# to compute next viewer position in orbit
	direction = 180 - (heading - 90);
	if (direction < 0) then
		direction = direction + 360;

	# compute new viewer x and y position from direction angle
	viewer.x = center.x + (radius * cosd(direction) );
	viewer.y = center.y + (radius * sind(direction) );

	# set scene with new viewer position and center on orbit center
	TNTsim3D.SetScene(viewer, center, 0);
	}

########################################################################
### SML function name predefined in TNTsim3D, called when right mouse 
### button is pressed.
########################################################################
func OnRightButtonPress() 
	{
	Exit();
	}