koobas.hobune.stream
Smooth object moving. Lerp issue
Hello. Sorry for my bad English. I'm making 2d game and I need to realize projectile motion in it. I wrote this code to make it work:
private float angle;
private float velocity;
private float g = 9.80665f;
private float t;
private float flightTime;
void Start()
{
// scale object
var scale = CameraSetter.YMax * 2 / 4;
transform.localScale = new Vector3(scale, scale, 0);
//set desirable parameters for projectile motion
t = 0;
var maxHeight = CameraSetter.YMax + CameraSetter.YMax/2;
var range = CameraSetter.XMax*2;
angle = CalculateAngle(maxHeight, range);
velocity = CalculateVelocity(range);
flightTime = CalculateFlightTime();
}
private float CalculateFlightTime()
{
return (2*velocity*Mathf.Sin(angle*Mathf.Deg2Rad))/g;
}
private float CalculateVelocity(float range)
{
return Mathf.Sqrt((range * g) / Mathf.Sin(angle * 2 * Mathf.Deg2Rad));
}
private float CalculateAngle(float maxHeight, float range)
{
return Mathf.Atan(4*maxHeight/range)*Mathf.Rad2Deg;
}
void Update()
{
t += Time.deltaTime;
var x = GetXv();
var y = GetYv();
transform.position = new Vector3(x, y, 0);
}
private float GetYv()
{
return ((velocity * t * Mathf.Sin(angle * Mathf.Deg2Rad)) - 0.5f * (g * (t * t))) - CameraSetter.YMax;
}
private float GetXv()
{
return (velocity * t * Mathf.Cos(angle * Mathf.Deg2Rad)) - CameraSetter.XMax;
}
This works fine to me: object starts moving from left bottom corner to right bottom corner with parabolic trajectory and maximum height in center (with coordinates x=0, y=orthographicSize/2). However, it's moving not smoothly, so i decided to do Lerp like this:
transform.position = Vector3.Lerp(transform.position, new Vector3(x, y, 0), Time.deltaTime);
instead of
transform.position = new Vector3(x, y, 0);
and this actually ruined the whole thing!! Trajectory now ends in somewhere near the center bottom with max height just about y=-orthographicSize/3 or something like that. Please explain me why Lerp is ruining trajectory and how can i fix it (i need working trajectory with smooth movement).
Can you please tell me what is CameraSetter's purpose?
CameraSetter is singleton object which calculates in Awake() distance from center of screen to edge of screen on both axes based on aspect ratio and ortho size. Y$$anonymous$$ax is ortho size and X$$anonymous$$ax is (ortho size multiply aspect). Therefore distance from left edge to right edge is (2 multiply X$$anonymous$$ax) and distance from top to bottom is (2 multiply Y$$anonymous$$ax).
That's because you're using Time.deltaTime as the fraction parameter in Lerp(). This is NOT an actual time value but the time in seconds it took to complete the last frame.
I didn't read up intensively on your code, but you could use your "t" variable instead as an example. In this case the object would move to the target position in exactly 1 second.
EDIT:
Try this out:
private const float MOVEMENT_TIME = 5.0f; // Should move for 5 seconds
void Update()
{
t += Time.deltaTime;
float lerpFraction = t / MOVEMENT_TIME;
var x = GetXv();
var y = GetYv();
transform.position = Vector3.Lerp(transform.position, new Vector3(x, y, 0), lerpFraction);
}
Thanks! It works perfect now! I'm sorry I cannot vote yet.
