Does anyone know how to make things float with different weights in reactor. I have an underwater scene that I need to make some objects float and react with other objects floating bye.

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram

It should work just the same as in the real world, as discovered by Archimedies.
It is the relative density between the liquid and the object. A reactor water object will start with a default density of 1, the equivelent of water’s density in the real world. If the object is more dense, it will sink, if it is less dense, it will float. The object’s density is defined by the mass divided by the volume. So for this to work, you must use an accurate realistic scale for both size and weight. Make sure the system units are set correctly and the reactor world settings, scale, gravity etc…
Put simply, if it is sinking, either increase the volume or decrease the mass, then it will float. Increasing the water’s density value will also make sinking objects float, but you will be straying form physically accurate simulation, unless of course it is not meant to be water, but a denser liquid, like molten metal.

I’m sorry I guess I didn’t clarify myself properly. The items are under the water.

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram

Can you explain in a bit more detail the effect you want? I’m not really clear about it. Usually an object in water will either sink or float, unless it has neutral bouyancy, that is the same density as water, like a submersible with it’s ballast tanks set at a neutral level. Then an object can just float within the water, not sinking or rising to the surface. An object with close to neutral bouyancy will float or sink very slowly. When you say floating by, do you mean as in with the tide, or through some other means of propulsion? With reactor, the tide could possibly be simulated with wind. It is possible that reactor is not the solution.

To get objects to float more like they’re underwater, I would just increase the gravity value in the Reactor world so they’re closer to 0 (ie. the standard value for gravity is -32’2 7/32” if you’re using feet, I would increase it to like -5’ to exaggerate the effect).

If you have reactor objects above water also, you’ll have to simulate the above water objects, change the gravity value and then simulate the underwater objects.

3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC

I see what you mean now. The items in the water (When it laying on top or below the water plane) act different than if they were in a scene without water. I want to have items under the water plan with lines attached to them as if they were tethered to the sea floor and have them float. I can then make different mass weights to allow them to float differently. This would then give the ability to 2 or 3 different items with buoyancy items attached and have them actually float in the water. If this items are in a scene without water they are subject to gravity, but if they are in a scene below the water plane they are subject to the water properties. Thank you for your help.

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram

If all the objects are floaters, you can fake it by reversing the gravity, so things fall up. you can set different masses for individual objects, bear in mind that because you are using reverse gravity, less dense (lighter) objects will have greater mass and vice-versa. So this is a non-physical method.
Or go with the physical approach, and use water, real world gravity, scale and masses. That way you can also have sinking and neutral objects, plus objects out of or falling in the water.

Your second option is what I’m after. I need to have floating, falling and neutral objects.

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram

Maybe MK-3D might know this one, but can you add buoyancy to a rope to make it float like an object under the water?

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram

As mentioned, the bouyancy of any object depends upon density, relative to the water. Density is dependant on Mass and Volume. So decreasing mass will make the object less dense and more likely to float. Also a bigger volume with the same mass is less dense.
Imagine a block of concrete and a block of wood, the same size, so the volume is the same, but the mass is different. What happens when you put them in water?
Now you have a bigger block of the same type of wood that has the same mass as the concrete block, but the volume is greater, it sill floats because the density is the same as the smaller wood block.
Water with a density of 1, 1m cube has a mass of 1 metric ton, thats 1000 reactor mass units (they are Kg).
So a 1m of concrete has a mass greater than 1000, it sinks.
The 1m wood cube is less than 1000, it floats.
A polystyrene cube is far less than 1000, it floats much better than the wood and would sit proud on the surface if it can reach there.
I’ve never tried doing floating ropes in reactor, not sure if it works. They do have a mass param, and the thickness would define some volume, will have to try it.

OK, Imagine you have a cable lowering some large Equipment into the ocean from a ship. The Equipment has cables attached to it with buoyancy nodes attached. The buoyancy nodes are to offset the weight of the equipment so the ROV can handle it without breaking an arm.  This equipment has hydraulic lines that need to be hooked up when the equipment is placed on the bottom of the ocean. The lines have to be heavy enough not to float and the buoyancy nodes have to be light enough to float. The problem is, I can get all of the other equipment to float just fine, but the cables/Hyd Lines want to float to the surface.  Adding mass to the ropes freaks out the ropes, and adjusting the water density/viscosity helps but I can’t get enough to fix the problem. I hope this clears up everything a little more. Sorry about the confusions.

D.R.
3ds Max 2011
Autodesk Inventor & AutoCAD
HP xw8600 Workstation
Windows XP Pro 64Bit
Dual Intel Xeon 2.83 E5440 GHz
8.00 GB of Ram