Physics Simulation - 3D Game Development Practical Introduction - page 301

The first thing you can notice in the script is the relatively high magnitude of ex-
plosionForce , which is reasonable since we are talking about an explosion that can destroy
a building. The radius in which the explosion takes effect is set by explosionRadius , which
means that only objects within this distance are affected by explosion force. This script
creates an explosion when a block is clicked. However, to make the explosion more obvious
and effective, we move for a short distance from the block position and perform the explo-
sion there. This distance is determined by explosionPosition , which is relative the position
of the target block that was clicked.
OnMouseClick()
handlesmouseclickonthedestructibleblockbyaddingexplosionforcetoallsurrounding rigid
body within the given radius. First step is to get all rigid bodies and storethem in allBodies
array. After that, explosionPos is computed by adding explosionPosition relative position
to the position of the block. The for loop in line 37 iterates over all rigid bodies and
finds the distance between each body and the computed explosionPos . If this distance is
less than explosionRadius , we send Destruct message to the rigid body and then call Ad-
dExplosionForce() . AddExplosionForce() takes 3 arguments: the strength of the explosion
which is explosionForce , the position of the explosion which is explosionPos , and the ra-
dius of explosion effect which is explosionRadius . The importance of sending Destruct
message is to unfreeze the rigid body, in case it has Destructible script attached to it.
Without this step, the explosion isn't going to have any effect on the rigid body. Illustration
73 shows a demo explosion. Notice that the effect of the explosion is purely physical, and
has no visual effects such as fire or smoke.