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I’ve been trying it and it seems like the ropes do work with water. I did a simple scene, there is water and a box with neutral bouyancy (100x50x50cm 250Kg), the box has two ropes attached to it with their other ends free. Both ropes are 3cm thick, but one is heavier than the other. So one floats, so it could be a polythene rope, the other sinks, so it could be a chain or leaded tow. It also seems that the thickness does alter the ropes volume. When I made the heavier rope 6cm thick, it floated, and i made the light rope 0.5cm think, it sank.
So in theory it should work. I think it would be best to keep to realistic physical scale with this.
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I’ve done a little more. Now there are two boxes, but made from a denser material, the size is the same (50x50x100cm, one quarter of the volume of a metric ton of water), but they weigh 400Kg, so they sink in water. But I have attached floating pellets to the ropes. The first box starts at the top of the water and has only two pellets, so sinks. The second box starts at the bottom of the water, but has four pellets which is enough to float it to the water surface.
I wil say I did get some ropes freaking out while setting up the sim, trying to float the second box. But I admit that was pilot error, because I forgot that I had “Do not affect RB” enabled where they are attached to the box. So they would never float it no matter what.
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Check this out. This is kind of what I’m attempting in one of the scenes. The Ropes need to sink and the Blue tank object and the ropes needs to be held up by the Yellow Buoyancy Capsules. I don’t want the Green Tank to be effected so it’s unyielding. Between the two ropes, the yellow buoyancy capsules should be floating in an arch shape. I can’t get the ropes to sink; they want to rise to the surface. Can please tell me what I’m doing wrong so I can get it right? If I can figure this out it should help me with other problems that I need to do.
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
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With some experimenting, I got it to work. I had to lower the rope’s thickness to 1cm because when I would use a mass value higher than 100kg, reactor would freak out. Lowering the thickness but keeping the same mass makes it denser so it will sink. I also lowered the mass of the blue tank a little because it was sinking with the bouyancy capsules and if I tried lowering their mass below 50kg to make them float more, reactor would freak out again.
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
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Scale is the key if you want this to work. That’s not just the sys units and dims of the models, but the object mass and Havok World settings too. These were left at the default settings, which are wrong for a metric (cm) scene. Gravity should be Z -980cm and World Scale 1m=100cm in Max. Then you need to se the object mass. The blue tank was set at 20 tons, very dense. And the floats were 50kg, more like ballast than floats.
I altered the Havok World to correct settings and adjusted the RB masses, I made the blue tank just over 1 ton and the floats at 0.7kg, that was as low as I could get without it freaking out. Again increasing the rope mass to make it sink caused a freakout, so I lowered the thickness, though they still render at 7cm.
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This is what I came up with. All the suggestions were very helpful, but none were what I was looking for. I used a chain of objects with a point to point constraint in reactor. This gave the ability to set mass for any object to get the results I was after. Different parts of the chain can have different masses to create different movement. After the keys are created then a spline is used and a skin modifier is applied using the chain of objects as a bone structure to make the rope/hose/cable. This is going to take some more refining but it does seem to be a good option. The point to point constraint is a lot more stable and stronger than the rope in reactor. Let me know what you think.
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
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