Physical objects which are large enough to be affected by energy constraints behave much differently under Havok 4. Scenario: Put the attached Hover script on a 10x10x1 cube in a Havok 1 sim. Make the object physical. The object will hover even if it starts out on the ground and with 0 initial energy. In a Havok 4 sim, a cube with 1/10 the mass (10x1x1) won't hover under the most favorable circumstances. There is more than an order of magnitude difference in the masses that are able to hover. I originally discovered that there were differences in energy when I checked to see whether the rate at which objects gained energy had changed, and it had. The following was my original post. But having discovered that the effects of the changes can be so large, I have modified the summary and upped the priority. ----------------------------------------------------------------------------------------------------------- The rate at which energy accumulates has changed in the Havok 4 beta. Previously, rezzed object gained energy at the rate of 200/mass units of energy per second. Under the Havok 4 beta, this has changed to 250/mass units of energy per second. This will change the behavior of any physical prims that are large enough that energy is a consideration. Or, if all energy-related constants have been scaled proportionately, it may still change the behavior of physical objects with scripts that use the old values. Scenario: Create a 5x5x5 meter cube and put the attached script on it. Take the cube into inventory and then rez it. The script will measure and report the energy growth rate as 200 Lindogram/sec units on a traditional sim and 250 Lindogram/sec units on a Havok 4 sim.