During a typical collision between two objects, the engine will compute the collision response; it will calculate the final velocity and position for each object.
However, there are instances when you ONLY want to know if two objects have collided and not in the resultant velocities. If such is the case, you can initialize the entity as a Collision Sensor using the method U4DEngine::U4DStaticModel::setIsCollisionSensor().
The snippet below shows how to set a 3D entity as a Collision Sensor:
//set as collision sensor myAstronaut->setIsCollisionSensor(true);
The engine will not compute the Collision Response for entities initialized as sensors. However, it will detect if the entity has collided.