/// <summary>
/// Add a body to the simulation.
/// </summary>
/// <param name="body">Body to add.</param>
public void addBody(Body body)
{
bodies.Add(body);
if (body.star)
nbStars++;
else
nbPlanets++;
}
private void drawBody(Graphics g, Body body, int absX, int absY, int absRadius)
{
/*
* The coordinates of the objects drawn to the screen are calculated from the up-left corner
* the coordinates of the bodies in the simulation are calculated from their center
* we do a correction on the offset and we transform it in integer (pixel)
*/
int x = (int)(absX - absRadius); //(px)
int y = (int)(absY - absRadius); //(px)
//Color
Brush brush = new SolidBrush(body.color);
//Draw body
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
g.FillEllipse(brush, x, y, absRadius*2, absRadius*2);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.Default;
brush.Dispose();
}
private void drawBody(Graphics g, Body body)
{
Point2D absPosition = relToAbsCoors(body.position.x, body.position.y);
int absRadius = radiusToAbs(body.radius, body.star);
drawBody(g, body, absPosition.x, absPosition.y, absRadius);
}
public void addBody(Body body)
{
//Transform the absolute mouse position in position relative to the center
//Find where this position is in the simulation model (Scaling)
body.position.x = (mouseX - centerX)*1/positionScale;
body.position.y = (mouseY - centerY)*1/positionScale;
body.speed = speed;
space.addBody(body);
}
/// <summary>
/// Do the collision of 2 bodies.
/// </summary>
/// <param name="A">Body A</param>
/// <param name="B">Body B</param>
private void collide(Body A, Body B)
{
if (A != B)
{
//A < B
if (A.mass < B.mass)
{
B.collide(A);
//explode(A, B, 1);
removeBody(A);
}
//A > B
else if (A.mass > B.mass)
{
A.collide(B);
//explode(A, B, 2);
removeBody(B);
}
//A == B
else
{
//explode(A, B, 0);
removeBody(A);
removeBody(B);
}
}
}
/// <summary>
/// Remove a body from the simulation.
/// </summary>
/// <param name="body">Body to remove.</param>
public void removeBody(Body body)
{
if (body.star)
nbStars--;
else
nbPlanets--;
bodies.Remove(body);
}
/// <summary>
/// Check if the body is in collision with another body.
/// The collisions detection depends on the collision scales:
/// Different scales for radius and distance doesn't result in "real" collision detection,
/// it will collide if it appear that they are colliding, not if it is really colliding in the simulation.
/// </summary>
/// <param name="body">The other body.</param>
/// <returns>True if there is a collision with the other body</returns>
public bool isColliding(Body body)
{
if (body != this)
{
//Distance between the 2 bodies possibly in collisions (Squared)
int distanceSquare = (int)((position - body.position).lengthSquared * positionScale * positionScale);
//Radius sum of the 2 bodies (Squared)
int radiusA = (int)(star ? radius * starRadiusScale : radius * bodyRadiusScale);
int radiusB = (int)(body.star ? body.radius * starRadiusScale : body.radius * bodyRadiusScale);
int sumRadiusSquare = (radiusA + radiusB) * (radiusA + radiusB);
if (distanceSquare < sumRadiusSquare)
return true;
}
return false;
}
/// <summary>
/// Do a perfecly inelastic collision another body.
/// </summary>
/// <param name="body">The other body.</param>
public void collide(Body body)
{
mass += body.mass;
//v = (m1*u1 + m2*u2)/(m1 + m2)
Vector2D newSpeed = (speed * mass + body.speed * body.mass) / (mass + body.mass);
speed = newSpeed;
colorAddition(body.color);
}
/*
* How it works
* ------------
* Fg = GMm/r^2 (Fg> = GMm/r^2 * r>unit)
* F = ma
* GMm/r^2 = ma
* a = -GM/r^2 (a> = -GM/r^2 * r>unit)
*
* v = v + a*dt
* x = x + v*dt
*/
/// <summary>
/// Calculate the acceleration produced by the gravity of a body from another.
/// </summary>
/// <param name="body">The other body</param>
/// <param name="dt">Time step (s)</param>
public void calcAcceleration(Body body, double dt)
{
if (this != body) //A body can't interact with itself
{
//r> = A.pos> - B.pos>
Vector2D radius = position - body.position;
//a> = -Gm/r^2 * r>
Vector2D acceleration = (-G * body.mass / radius.lengthSquared) * radius.getUnitVector();
speed += acceleration * dt; //v> = v> + a>*dt
}
}
