private void UpdateRopeSimulation()
{
Vector3 gravityVec = new Vector3(0f, -9.81f, 0f);
float t = Time.fixedDeltaTime;
//Move the first section to what the rope is hanging from
RopeSection firstRopeSection = allRopeSections[0];
firstRopeSection.pos = whatTheRopeIsConnectedTo.position;
allRopeSections[0] = firstRopeSection;
//Move the other rope sections with Verlet integration
for (int i = 1; i < allRopeSections.Count; i++)
{
RopeSection currentRopeSection = allRopeSections[i];
//Calculate velocity this update
Vector3 vel = currentRopeSection.pos - currentRopeSection.oldPos;
//Update the old position with the current position
currentRopeSection.oldPos = currentRopeSection.pos;
//Find the new position
currentRopeSection.pos += vel;
//Add gravity
currentRopeSection.pos += gravityVec * t;
//Add it back to the array
allRopeSections[i] = currentRopeSection;
}
//Make sure the rope sections have the correct lengths
for (int i = 0; i < 20; i++)
{
ImplementMaximumStretch();
}
}
protected Rope CreateRopeWithSectionType(RopeSection sectionPrefab)
{
// Create Rope Container
Rope ropeContainer = Instantiate(ropePrefab, transform.position, Quaternion.identity) as Rope;
ropeContainer.name = "Rope " + index;
// Create First section and remove its joint
RopeSection lastSection = Instantiate(sectionPrefab, new Vector3(ropeEnds.x, transform.position.y, 0), Quaternion.identity) as RopeSection;
// Connect to Rope Container
ropeContainer.AddSection(lastSection);
// Count variables and section length
float offset = 0f;
float sectionLength = lastSection.transform.localScale.x - 0.05f;
// Calculate number of sections based on draw length
float distance = ropeEnds.y - ropeEnds.x;
int num = Mathf.CeilToInt(distance / sectionLength);
while (num > 0)
{
// Count
num--;
offset += sectionLength;
// Add new Section
RopeSection newSection = Instantiate(sectionPrefab, new Vector3(ropeEnds.x + offset, transform.position.y, 0), Quaternion.identity) as RopeSection;
newSection.ConnectTo(lastSection);
// Add to Rope Container
ropeContainer.AddSection(newSection);
// Reset for next iteration
lastSection = newSection;
}
return(ropeContainer);
}
private void UpdateRopeSimulation(List <RopeSection> allRopeSections, float timeStep)
{
//Move the last position, which is the top position, to what the rope is attached to
RopeSection lastRopeSection = allRopeSections[allRopeSections.Count - 1];
lastRopeSection.pos = whatTheRopeIsConnectedTo.position;
allRopeSections[allRopeSections.Count - 1] = lastRopeSection;
//
//Calculate the next pos and vel with Forward Euler
//
//Calculate acceleration in each rope section which is what is needed to get the next pos and vel
List <Vector3> accelerations = CalculateAccelerations(allRopeSections);
List <RopeSection> nextPosVelForwardEuler = new List <RopeSection>();
//Loop through all line segments (except the last because it's always connected to something)
for (int i = 0; i < allRopeSections.Count - 1; i++)
{
RopeSection thisRopeSection = RopeSection.zero;
//Forward Euler
//vel = vel + acc * t
thisRopeSection.vel = allRopeSections[i].vel + accelerations[i] * timeStep;
//pos = pos + vel * t
thisRopeSection.pos = allRopeSections[i].pos + allRopeSections[i].vel * timeStep;
//Save the new data in a temporarily list
nextPosVelForwardEuler.Add(thisRopeSection);
}
//Add the last which is always the same because it's attached to something
nextPosVelForwardEuler.Add(allRopeSections[allRopeSections.Count - 1]);
//
//Calculate the next pos with Heun's method (Improved Euler)
//
//Calculate acceleration in each rope section which is what is needed to get the next pos and vel
List <Vector3> accelerationFromEuler = CalculateAccelerations(nextPosVelForwardEuler);
List <RopeSection> nextPosVelHeunsMethod = new List <RopeSection>();
//Loop through all line segments (except the last because it's always connected to something)
for (int i = 0; i < allRopeSections.Count - 1; i++)
{
RopeSection thisRopeSection = RopeSection.zero;
//Heuns method
//vel = vel + (acc + accFromForwardEuler) * 0.5 * t
thisRopeSection.vel = allRopeSections[i].vel + (accelerations[i] + accelerationFromEuler[i]) * 0.5f * timeStep;
//pos = pos + (vel + velFromForwardEuler) * 0.5f * t
thisRopeSection.pos = allRopeSections[i].pos + (allRopeSections[i].vel + nextPosVelForwardEuler[i].vel) * 0.5f * timeStep;
//Save the new data in a temporarily list
nextPosVelHeunsMethod.Add(thisRopeSection);
}
//Add the last which is always the same because it's attached to something
nextPosVelHeunsMethod.Add(allRopeSections[allRopeSections.Count - 1]);
//From the temp list to the main list
for (int i = 0; i < allRopeSections.Count; i++)
{
allRopeSections[i] = nextPosVelHeunsMethod[i];
//allRopeSections[i] = nextPosVelForwardEuler[i];
}
//Implement maximum stretch to avoid numerical instabilities
//May need to run the algorithm several times
int maximumStretchIterations = 2;
for (int i = 0; i < maximumStretchIterations; i++)
{
ImplementMaximumStretch(allRopeSections);
}
}
public void InsertSection(RopeSection rs, int index)
{
sections.Insert(index, rs);
rs.transform.SetParent(transform);
}
public void AddSection(RopeSection rs)
{
sections.Add(rs);
rs.transform.SetParent(transform);
}