Individual disabling of fluid calculations #2542
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IntroHi, I am trying to build a model of a quadcopter. I have specific profiles for rotor power and thrust vs. speed so I have modelled bodies that represent the inertia of the rotors and have two actuaors on the joint to the quad's body representing the rotor drag and motor, which are set at each step outside of the simulation. My setupMujoco 3.3.0, Windows 11 My questionI would like to be able to disable the fluid physics calculations for the geometry that I have representing the quad's rotors, but maintain it for the rest of the body of the quad. Is there a way to selectively disable the fluild physics calculations? Minimal model and/or code that explain my questionHere is a test model where I have tried setting the fluidshape to none and ellipsoid and fluidcoef to 0 for some cylindrical plates in a dense medium. Neither of these produces the behaviour I am looking for where the plate falls straight down. The first and second (red and green) appear to behave in the same way, while the the third (blue) moves differently, but is certainly still affected by some form of fluid forces. <mujoco model="fluid_test" >
<option density="1000" viscosity="1e-3" integrator="RK4" />
<asset>
<texture type="2d" name="groundplane" builtin="checker" mark="edge" rgb1="0.2 0.3 0.4" rgb2="0.1 0.2 0.3"
markrgb="0.8 0.8 0.8" width="300" height="300"/>
<material name="groundplane" texture="groundplane" texuniform="true" texrepeat="5 5" reflectance="0.2"/>
</asset>
<worldbody>
<body name="plate" pos="0 0 1" euler="30 0 0 ">
<freejoint/>
<geom type="cylinder" size=".5 .01" rgba=".7 .5 .5 1" />
</body>
<body name="plate_none" pos="2 0 1" euler="30 0 0 ">
<freejoint/>
<geom type="cylinder" size=".5 .01" rgba=".5 .7 .5 1" fluidshape="none" fluidcoef="0 0 0 0 0"/>
</body>
<body name="plate_ellipsoid" pos="4 0 1" euler="30 0 0 ">
<freejoint/>
<geom type="cylinder" size=".5 .01" rgba=".5 .5 .7 1" fluidshape="ellipsoid" fluidcoef="0 0 0 0 0"/>
</body>
<geom name="floor" size="0 0 0.05" type="plane" material="groundplane"/>
</worldbody>
</mujoco>Confirmations
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Replies: 1 comment 2 replies
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Unfortunately there is currently no way to entirely disable the fluid forces. I guess we should add that |
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Within the definition of the geoms, rather than fluidshape="none" resulting in the less inertia-based fluid force model being activated, changing the name to "inertia" and then having "none" be the totally deactivated state would make sense to me. Of course that would have potential backwards-comaptibility issues where some old models would need to be updated. At the moment I do not have the expertise to submit a proposed change to mujoco that would implement that. |
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The issue is that one fluid model is at the geom level, while the other is at the body level |
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Unfortunately there is currently no way to entirely disable the fluid forces. I guess we should add that