A specific setup problem

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Re: A specific setup problem

Postby Julio Jerez » Wed Jul 05, 2017 8:47 pm

I did not ready it, but I believe what I was trying to say Is that, using torque to control a vehicle is cheating, because there are very few object that can generates actual torque in nature.
one such object is a Gyroscope and other are induction electric motors,
other that that a torque is a mathematical forces. therefore using the direct torque to control an aircraft is no right if you are looking for realism.

this si such a common practice that it is have a name, when I was in school it was called Dynamic, but now I see by the same resultant force.
https://en.wikipedia.org/wiki/Net_force

so basically each time you have a bunch of forces acting of a body, you can replace it with

f = sum of all fi at the origion,
t = sum of (pi - p0) x fi

that all there is to it.
so in your case the force are the thrusters, that have a point and a directions
and how the get applied mathematically is using those tow formulae.

the second method let you manipulate individual thrusters, while applying torque is magic unless you use Gyroscope , which some sattetiles do use .
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Re: A specific setup problem

Postby misho » Wed Jul 05, 2017 11:39 pm

Thanks Julio,

I absolutely agree. The whole point of my sim is "As real as it gets" :) So far, I have "cheated" by applying torques over principal axis of the body, so that the roll, yaw and pitch were always "perfect", without any linear movement, just rotational.

What I want to do is, define thrusters (or, I let users define them) that are placed all over the spacecraft (RCS, reaction control system), and define "groups" that fire together depending if you want roll, pitch or yaw, or translational movement. In real world, these controls are not perfect, because CG of the spacecraft can move, depending on the expenditures of the consumables (fuel, water, air) or even movement of crew around the capsule. This will be simulated "as real as it gets" when I define my thrusters as a sum of forces, instead of "precise" axial torques. And sure, there will probably be some linear movement, but that's real life :wink:

And yes, the satellite gyro is called, appropriately, CMG (control moment gyro)

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Re: A specific setup problem

Postby JoeJ » Thu Jul 06, 2017 1:32 am

Julio Jerez wrote:I do not think so, cpu are far superior in every way than GPU, branch prediction, super scalar, pipe lined, way associative cache lines, and goes on an on.


Yeah, but that's a lot of bloat made to make any general purpose code faster.
GPU programming puts more responsibility and constraints to the programmer and the architecture suits not every algorithm, but in many cases the simpler GPU architecture wins over the complex CPU.

My GI stuff is general purpose, i do not use rasterization nor texture filtering, i don't have simple shaders where threads can operate independent of each other, i have tons of too small workloads problems, but still my GPU is 50 times faster than the CPU.

It only depends on the task which one is suited better.
Collision detection and physics in general is something that might work well on GPUs now (at least for AMD), but the APIs fail. We need to be able to generate work for GPU dynamically on GPU including barriers, and we need proper async compute to execute small tasks in parallel.
Up to now the gaming industry has failed miserabely to utilize GPU compute power so there is too little demand for this.

But i agree discrete GPUs will disappear (i always thought NV went mobile because they have no x86 license so no future in PC gaming because of this, but vendors could work closer together to connect their modules).
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