Orbiter-Forum [SDK Question] Touchdown points definition 2016
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 11-14-2016, 01:43 PM #106 gattispilot Addon Developer Thanks. So the suspension animation will change? So on the LER it has 6 wheels. So each should changed based on what?
 11-14-2016, 02:03 PM #107 jedidia shoemaker without legs Quote: Oh I would think that the vessel would be at the surface. Yes, but since the touchdown points are simulating suspension, your altitude will still vary. As long as your wheels don't account for that, they'll dip into the ground. Currently this is a bit tough to do (see my last few posts), so I hope the Doctor will implement some way to let us know the current compression of a touchdown point in the future.
 11-14-2016, 02:07 PM #108 Urwumpe Certain Super User Quote: Originally Posted by gattispilot  Thanks. So the suspension animation will change? So on the LER it has 6 wheels. So each should changed based on what? To explain you what jedidia already found out: There is no way right now to query the current positions of the touchdown points from Orbiter to solve the animation. You only tell Orbiter with your definition: With 0N weight force on the suspension, your wheel would be at this position. And you tell it: By compressing the suspension by one meter, the spring force grows from 0N to x N. double the distance and the force doubles. Hookes Law implemented in Orbiters API. One solution: You know at rest on Earth your touchdown point will be at a known position in the mesh. You know your spacecraft will weight about m kg. You have a spring constant of c. So, in your definition you add simply the following distance to your touchdown point in the mesh: So, you need to place your mesh right now either in a way, that it looks correct at equilibrium (all oscillations damped, flat surface, all springs compressed by weight). Or you calculate yourself, how far away each wheel is from the surface and animate it accordingly (which is the Pandoras Box of all solutions, because solving every small subproblem creates new problems to solve) Also Orbiter uses a much simpler way of solving the suspension mechanisms (A simple linear spring, no unsprung weight) than it actually is in reality. Could be important for the rover animations, but I doubt anybody except mechanical engineers would notice the difference. Or Jeremy Clarkson. Last edited by Urwumpe; 11-14-2016 at 02:14 PM.
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 11-14-2016, 02:19 PM #109 gattispilot Addon Developer Thanks. I guess I will wait. But nothing explains why my crawler spins around on the z axis
 11-14-2016, 02:21 PM #110 Urwumpe Certain Super User Quote: Originally Posted by gattispilot  Thanks. I guess I will wait. But nothing explains why my crawler spins around on the z axis We have one potential explanation in SSU, which can be summarized as: There is no stable solution by Orbiters iterative solver to the differential equation system of the touchdown points because the initial guess presented in the scenario file is too far away from the solution, and thus, the PDE does not converge. I suspect this applies especially to vehicles where the following factors make it much harder to find a solution: High mass Huge spring constant Last edited by Urwumpe; 11-14-2016 at 02:24 PM.
 11-14-2016, 02:27 PM #111 gattispilot Addon Developer ? Is there a way to make a vessel with no springs. Like a base has no springs. I could understand if I placed the crawler and it was ok. But then as it moved it spun around. But this happens when I place it.
 11-14-2016, 03:27 PM #112 Urwumpe Certain Super User Quote: Originally Posted by gattispilot  ? Is there a way to make a vessel with no springs. Like a base has no springs. I could understand if I placed the crawler and it was ok. But then as it moved it spun around. But this happens when I place it. Use the old SetTouchdownPoints function?
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 11-14-2016, 03:35 PM #113 gattispilot Addon Developer Quote: Originally Posted by Urwumpe  Use the old SetTouchdownPoints function? I used the same touchdown points from 2010. In 2010 it works great but not in 2016. Same mesh in both.
 11-14-2016, 04:39 PM #114 Urwumpe Certain Super User Quote: Originally Posted by gattispilot  I used the same touchdown points from 2010. In 2010 it works great but not in 2016. Same mesh in both. You only use the same numbers. You are not using the same API functions. You are not even using the same numbers for the same entity in the Orbiter API. The touchdown points in one function are different to the touchdown points in the other. Its a bit said that I have to tell you this again but: Stop guessing. Stop fooling yourself. Know what the hell you are doing. Read the manual about what the functions do, which you want to use. Know what the numbers, which you give to Orbiter mean in that context. Be precise. Even a single changed word in a definition can change everything. PS: And you should already know that the meshes in Orbiter doesn't matter. I can replace the Space Shuttle mesh in SSU by Donald Trump nude in Superman pose and it will still fly like a Space Shuttle. It only feels wrong.
 11-14-2016, 04:52 PM #115 gattispilot Addon Developer I have this in the class; Code: void SLSCRAWLER::clbkSetClassCaps(FILEHANDLE cfg) { SetEmptyMass(2721000); SetSize(40); SetPMI(_V(133, 189, 89)); SetSurfaceFrictionCoeff(0.005, 0.5); SetRotDrag (_V(0, 0, 0)); SetCW(0, 0, 0, 0); SetPitchMomentScale(0); SetBankMomentScale(0); SetLiftCoeffFunc(0); SetTouchdownPoints(_V(0, .001, 20), _V(-15, .001, -20), _V(15, .001, -20));; This is the only place that sets the touchdown. Since in works in sc3/4 I wonder if it something else The meshes do matter as far as the orientation. Last edited by gattispilot; 11-14-2016 at 04:54 PM.
 11-14-2016, 04:59 PM #116 Urwumpe Certain Super User Quote: Originally Posted by gattispilot  The meshes do matter as far as the orientation. No, not at all. Rotate the mesh by 180°, and your vessels Z-axis will still point forward. It only looks different from outside.
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 11-15-2016, 11:51 AM #118 gattispilot Addon Developer Well. In my case it wasn't the touchdown points casuing the issue. I gutted the cpp and h. So basic info telling which mesh. The issue is on how it moves. Shuttle A has code where the touchdown and gear move.
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 11-15-2016, 02:49 PM #119 mike-c Orbinaut Quote: Originally Posted by gattispilot  Well. In my case it wasn't the touchdown points casuing the issue. I gutted the cpp and h. So basic info telling which mesh. The issue is on how it moves. Shuttle A has code where the touchdown and gear move. Anyway, good news if your crawler is crawling now. will follow your hint
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 11-25-2016, 05:14 PM #120 gattispilot Addon Developer Not sure why making the Y value more negative raises the vessel above the ground? You can see the lower value is 0 Code: SetTouchdownPoints(_V(0, .001, 20), _V(-15, .001, -20), _V(15, .001, -20));; put the vessel on the ground. Code: SetTouchdownPoints(_V(0, 5.45, 20), _V(-15, 5.45, -20), _V(15, 5.45, -20));; but this places the mesh/vessel into the ground. if I use this: Code: SetTouchdownPoints(_V(0, -15.55, 20), _V(-15, -15.45, -20), _V(15, -15.45, -20));; I should be 12.17 alt. and about 8 degrees down in pitch. not sure why?
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