obj_shell_step_event

/// @description Update shell x, y, z

// shell is not immediately armed, arming = 0 is considered armed
if (arming > 0) arming -=1;

// update time since shell was fired
time_of_flight += 1 / room_speed;

// gravity
var g = -9.8 * 10;

// update distance_travelled
distance_travelled = velocity_h * time_of_flight;

show_debug_message("Distance travelled: " + string(distance_travelled) + " at a time of " + string(time_of_flight));

// update horizontal axises
x = origin_x + lengthdir_x(distance_travelled, direction);
y = origin_y + lengthdir_y(distance_travelled, direction);

// this formula is for parabolic trajectory, not used, doesn't account for degrees or radians properly
//var displacement_z = ( tan(theta) * time_of_flight - (g / ( 2 * power(v, 2) * sqr(cos(theta)) ) ) * power(time_of_flight, 2) );

// convert velocity per tick to velocity per second
var v = shell_velocity * room_speed;

// vertical displacement at point in time, this formula is for z displacement
var displacement_z = ( (velocity_v * time_of_flight) + 0.5 * (g) * sqr(time_of_flight) );// *-1

// update z axis
z = origin_z + displacement_z;

// check if shell is under water
if (z < 0) is_under_water = true;

// update depth to be opposite of z, in gms negative depth is closer to camera, while positive z is above water line
depth = -1 * z