Bullet Queries¶

Ray Test¶

Raycasting is to shoot a ray from one position (the from-position) to another position (the to-position). Both the from-position and the to-position have to be specified in global coordinates. The ray test methods will then return a result object which contains information about which objects the ray has hit.

There are two different ray test method: The first method (rayTestAll) returns all collision objects hit by the ray. But sometimes we are only interested in the first collision object hit by the ray. Then we can use the second ray test method (rayTestClosest).

Example for closest hit:

pFrom = Point3(0, 0, 0)
pTo = Point3(10, 0, 0)

result = world.rayTestClosest(pFrom, pTo)

print result.hasHit()
print result.getHitPos()
print result.getHitNormal()
print result.getHitFraction()
print result.getNode()

Example for all hits:

pFrom = Point3(0, 0, 0)
pTo = pFrom + Vec3(1, 0, 0) * 99999

result = world.rayTestAll(pFrom, pTo)

print result.hasHits()
print result.getClosestHitFraction()
print result.getNumHits()

for hit in result.getHits():
  print hit.getHitPos()
  print hit.getHitNormal()
  print hit.getHitFraction()
  print hit.getNode()

Often users want to pick or select an object by clicking on it with the mouse. We can use the rayTestClosest to find the collision object which is “under” the mouse pointer, but we have to convert the coordinates in camera space to global coordinates world space. The following example shows how this can be done.

# Get to and from pos in camera coordinates
pMouse = base.mouseWatcherNode.getMouse()
pFrom = Point3()
pTo = Point3()
base.camLens.extrude(pMouse, pFrom, pTo)

# Transform to global coordinates
pFrom = render.getRelativePoint(base.cam, pFrom)
pTo = render.getRelativePoint(base.cam, pTo)

Sweep Test¶

The sweep test is similar to the ray test. There are two differences: (1) The sweep test does not use an infinite thin ray, like the ray test, but checks for collisions with a convex shape which is “moved” along the from from-position to to-position. (2) The sweep test wants to have “from” and “to” specified as TransformState. The sweep test can for example be used to predict if an object would collide with something else if it was moving from it’s current position to some other position.

Example for sweep testing:

tsFrom = TransformState.makePos(Point3(0, 0, 0))
tsTo = TransformState.makePos(Point3(10, 0, 0))

shape = BulletSphereShape(0.5)
penetration = 0.0

result = world.sweepTestClosest(shape, tsFrom, tsTo, penetration)

print result.hasHit()
print result.getHitPos()
print result.getHitNormal()
print result.getHitFraction()
print result.getNode()

Contact Test¶

There are two contact tests. One which checks if a collision objects is in contact with other collision objects, and another which checks for a pair of collision objects if they are in contact.

Example for contact testing:

body1 = BulletRigidBodyNode("body1")
...

body2 = BulletRigidBodyNode("body2")
...

result = world.contactTest(node1)
result = world.contactTestPair(node1, node2)

print result.getNumContacts()

for contact in result.getContacts():
  print contact.getNode0()
  print contact.getNode1()

  mpoint = contact.getManifoldPoint()
  print mpoint.getDistance()
  print mpoint.getAppliedImpulse()
  print mpoint.getPositionWorldOnA()
  print mpoint.getPositionWorldOnB()
  print mpoint.getLocalPointA()
  print mpoint.getLocalPointB()