Hi, ruochun
The RotateQuat(const float4& quat, const float3& axis, const
float& theta) just need to set the rotating axis, so does the rotating
point is (0, 0, 0) default? If I want to modify the rotating point, how to
implement it ?
Best regards,
Wenxuan
在2024年7月1日星期一 UTC+8 16:18:50<Ruochun Zhang> 写道：
> Hi Wenxuan,
>
> Regarding debugging on Linux, I recommend seeking professional assistance.
> However, I find that VSCode's GUI for stepping through code is sufficient
> for my needs.
>
> For enforcing motion on an entity step-by-step, use
> *DoDynamics(step_size)* or *DoStepDynamics()* instead of
> *DoDynamics(frame_duration)*. This way, you can count the number of steps
> and use if statements to control outputs. The RotatingDrum demo provides a
> good example of this.
>
> The performance impact should be minimal, as DEME is designed for
> fine-grain operations like these to enable more flexible co-simulation. The
> two GPU streams synchronize only with *DoDynamicsThenSync()*, not
> *DoDynamics()*. Also, transferring the explicit position and velocity of
> one or two entities to GPUs at each step introduces only a small and
> manageable overhead, too.
>
> Regarding your script, it doesn't fully implement my specified formula. I
> didn't use *fabs*, and the linear velocity should have a scaling factor
> of 5, which seems to be missing. Even with my specified formula, I can't
> guarantee its correctness (without knowing details like what the coordinate
> system is, and what the "expected results" is). But more realistically,
> it's that I cannot do your research for you. You see, this is becoming more
> of a consulting task than troubleshooting.
>
> I suggest starting simple, using only one of the implemented motions,
> verifying it works as expected, and then gradually adding components of the
> second one to approach your desired outcome.
>
> Thank you,
>
> Ruochun
>
> On Saturday, June 29, 2024 at 2:16:35 AM UTC+8 [email protected] wrote:
>
>> Hi, Ruochun
>>
>> I have tried it, but the geometric motion doesn't seem to achieve
>> the expected result. Can you help me troubleshoot the error? Ths mesh obj
>> file are attached.
>>
>> #include <core/ApiVersion.h>
>> #include <core/utils/ThreadManager.h>
>> #include <DEM/API.h>
>> #include <DEM/HostSideHelpers.hpp>
>> #include <DEM/utils/Samplers.hpp>
>>
>> #include <cstdio>
>> #include <chrono>
>> #include <filesystem>
>>
>> using namespace deme;
>> using namespace std::filesystem;
>>
>> int main()
>> {
>> DEMSolver DEMSim;
>> DEMSim.SetVerbosity(STEP_METRIC);
>> // For general use cases, you want to set the verbosity to INFO: It's
>> also a bit faster than STEP_METRIC.
>> // DEMSim.SetVerbosity(INFO);
>> DEMSim.SetOutputFormat(OUTPUT_FORMAT::CSV);
>> DEMSim.SetOutputContent(OUTPUT_CONTENT::ABSV);
>> DEMSim.SetMeshOutputFormat(MESH_FORMAT::VTK);
>>
>> // If you don't need individual force information, then this option makes
>> the solver run a bit faster.
>> DEMSim.SetNoForceRecord();
>>
>> // E, nu, CoR, mu, Crr...
>> auto mat_type_mixer = DEMSim.LoadMaterial({{"E", 1e8}, {"nu", 0.3}, {
>> "CoR", 0.6}, {"mu", 0.5}, {"Crr", 0.0}});
>> auto mat_type_granular = DEMSim.LoadMaterial({{"E", 1e8}, {"nu", 0.3}, {
>> "CoR", 0.6}, {"mu", 0.2}, {"Crr", 0.0}});
>> // If you don't have this line, then mu between mixer material and
>> granular material will be 0.35 (average of the
>> // two).
>> DEMSim.SetMaterialPropertyPair("mu", mat_type_mixer, mat_type_granular,
>> 0.5);
>>
>> float step_size = 5e-5;
>> const double world_size = 10;
>> const float chamber_height = world_size / 3.;
>> const float fill_height = chamber_height;
>> const float chamber_bottom = -world_size / 2.;
>> const float fill_bottom = chamber_bottom + chamber_height;
>>
>> DEMSim.InstructBoxDomainDimension(world_size, world_size, world_size);
>> DEMSim.InstructBoxDomainBoundingBC("all", mat_type_granular);
>>
>>
>> auto mixer = DEMSim.AddWavefrontMeshObject((GET_DATA_PATH() /
>> "mesh/Chute_Rotating.obj").string(), mat_type_mixer);
>> std::cout << "Total num of triangles: " << mixer->GetNumTriangles() <<
>> std::endl;
>> mixer->SetFamily(10);
>> mixer->InformCentroidPrincipal(make_float3(0, 0, 6.793), make_float4(0, 0,
>> 0, 1));
>>
>>
>> double w1 = 3.14159;
>> double w2 = 1.0;
>> std::string angVel_x = "fabs(1.0 * cos(deme::PI * t))";
>> std::string angVel_y = "fabs(1.0 * sin(deme::PI * t))";
>> std::string angVel_z = "deme::PI";
>>
>>
>> std::string vel_x = "(1.0 * cos(1.0 * t) * sin(deme::PI * t) + sin(1.0 *
>> t) * deme::PI * cos(deme::PI * t))";
>> std::string vel_y = "(-1.0 * cos(1.0 * t) * cos(deme::PI * t) + sin(1.0
>> * t) * deme::PI * sin(deme::PI * t))";
>> std::string vel_z = "0";
>>
>> DEMSim.SetFamilyPrescribedAngVel(10, angVel_x, angVel_y, angVel_z);
>> DEMSim.SetFamilyPrescribedLinVel(10, vel_x, vel_y, vel_z);
>>
>>
>>
>>
>> float granular_rad = 0.005;
>> // Calculate its mass and MOI
>> float mass = 2.6e3 * 5.5886717; // in kg or g
>> float3 MOI = make_float3(2.928, 2.6029, 3.9908) * 2.6e3;
>> std::shared_ptr<DEMClumpTemplate> template_granular = DEMSim.
>> LoadClumpType(mass, MOI, GetDEMEDataFile("clumps/3_clump.csv"),
>> mat_type_granular);
>> template_granular->Scale(granular_rad);
>>
>> // Track the mixer
>> auto mixer_tracker = DEMSim.Track(mixer);
>>
>>
>>
>> DEMSim.SetInitTimeStep(step_size);
>> DEMSim.SetGravitationalAcceleration(make_float3(0, 0, -9.81));
>>
>> // Initialize the simulation system
>> DEMSim.Initialize();
>>
>> path out_dir = current_path();
>> out_dir += "/DEMdemo_RotatingChute";
>> create_directory(out_dir);
>>
>> float sim_end = 2.0;
>> unsigned int fps = 20;
>> float frame_time = 1.0 / fps;
>>
>> std::cout << "Output at " << fps << " FPS" << std::endl;
>> unsigned int currframe = 0;
>>
>>
>> // mixer_tracker->SetOriQ(make_float4(0, 0, 0, 1));
>> for (float t = 0; t < sim_end; t += frame_time) // 0.05迭代一次
>> {
>>
>> std::cout << "Position: " << mixer_tracker->GetPos()[0] << " " <<
>> mixer_tracker->GetPos()[1] << " " << mixer_tracker->GetPos()[2] << std::
>> endl;
>> std::vector<float> Qua = mixer_tracker->GetOriQ(); // x, y, z, w
>> // std::cout << Qua[0] << " " << Qua[1] << " " << Qua[2] << " " << Qua[3]
>> << std::endl;
>>
>>
>> std::cout << "Frame: " << currframe << std::endl;
>> char filename[200], meshfilename[200], cnt_filename[200];
>> sprintf(filename, "%s/DEMdemo_output_%04d.csv", out_dir.c_str(),
>> currframe);
>> sprintf(meshfilename, "%s/DEMdemo_mesh_%04d.vtk", out_dir.c_str(),
>> currframe);
>> sprintf(cnt_filename, "%s/Contact_pairs_%04d.csv", out_dir.c_str(),
>> currframe++);
>>
>> DEMSim.WriteMeshFile(std::string(meshfilename));
>> DEMSim.DoDynamics(frame_time);
>>
>> }
>>
>> std::cout << "DEMdemo_RotatingChute simulating complete!" << std::endl;
>> return 0;
>> }
>>
>> 在2024年6月29日星期六 UTC+8 00:33:30<simboys> 写道：
>>
>>> Hi, Ruochun
>>>
>>> Thank you for your reply, I wiil try it. By the way, can you
>>> share me the method how to debug the code step-by-step in linux? In
>>> addition, if I use the DEMTracker to set the location and rotation of
>>> geometry at each time step, will this affect computational efficiency? And
>>> how to set the location of geometry at each time step? From the
>>> demo, DoDynamics(frameTime) is many times longer than timestep, and if we
>>> set the frameTime by timestep, it will result in a huge data file.
>>>
>>> Best regards,
>>> Wenxuan
>>>
>>> 在2024年6月27日星期四 UTC+8 23:06:58<Ruochun Zhang> 写道：
>>>
>>>> Hi Wenxuan,
>>>>
>>>> 1. When you load a mesh or an analytical object, it's by default in
>>>> family 255, a reserved and automatically fixed family. You probably
>>>> changed
>>>> your mesh into a family that does not have any motion prescription, then
>>>> in
>>>> that case it follows the "normal physics" like all the particles you load
>>>> in, including falling under gravity. If you wish to fix that family, just
>>>> use *SetFamilyFixed*.
>>>>
>>>> 2. This is more complicated. First, we have to understand that in DEME,
>>>> strictly speaking, objects work with their principal frames of inertia
>>>> (centered at CoM, having a diagonal inertia matrix). This is a current
>>>> limitation due to how the inertia matrix-defining APIs are designed: you
>>>> can only input the principal moments of inertia. But this also means that
>>>> setting the frame correctly is not necessary if you completely prescribe
>>>> the motion of that object (a.k.a. this object does not respond to
>>>> physics),
>>>> and you don't care about getting a torque reading. However, in your case,
>>>> I
>>>> suggest you do so, since you'll prescribe a complex motion, and
>>>> standardizing the frame to use at least the CoM frame can save you some
>>>> head-scratching. I suggest that you make it such that in the mesh file you
>>>> load in, the (0,0,0) point is right at the CoM of this mesh; but if not,
>>>> you can adjust the CoM and principal axes with
>>>> *InformCentroidPrincipal* after loading in the mesh.
>>>>
>>>> After that is taken care of, you need to combine the two rotations into
>>>> a rotation about this object's own CoM and a linear translation of this
>>>> object's CoM (because family motion prescription allows for setting these
>>>> two motions only). Use your MBD knowledge to do that. I don't guarantee
>>>> the
>>>> correctness of this, but some back-of-the-envelop calculation seems to put
>>>> the angular velocity to be (w2×cos(w1×t), w2×sin(w1×t), w1), and the
>>>> linear
>>>> velocity to be 5×(w2×cos(w2×t)×sin(w1×t)+sin(w2×t)×w1×cos(w1×t),
>>>> -w2×cos(w2×t)×cos(w1×t)+sin(w2×t)×w1×sin(w1×t), 0). Again, please verify
>>>> yourself. After that, prescribe the object's family's motion using it.
>>>>
>>>> But if this is too complicated and you can write your code to calculate
>>>> the location and quaternion of this object at any given *t *(which for
>>>> some people is easier than mathematically deriving the analytical
>>>> expression for the linear and rotational motions), then you can set this
>>>> object fixed, then use the tracker methods *SetPos *and *SetOriQ *to
>>>> enforce the location and rotation of this object *at each time step*.
>>>> It should achieve the same assuming this object is not moving at a very
>>>> high velocity.
>>>>
>>>> Thank you,
>>>> Ruochun
>>>>
>>>> On Thursday, June 27, 2024 at 2:49:43 PM UTC+8 [email protected]
>>>> wrote:
>>>>
>>>>> Hi,
>>>>> I want to achieve a composite rotational motion of a geometric
>>>>> body, as follows
>>>>> Motion 1: Rotate at a speed of w1 rad/s, with the rotation axis being
>>>>> the z-axis
>>>>> Motion 2: Rotate at a speed of w2 rad/s, with a rotation vector of [1
>>>>> * cos (w1 * time), 1 * sin (w1 * time), 0], and an action point of [0, 0,
>>>>> 5], as shown in attached figure.
>>>>> [image: rotating_Chute.png]
>>>>>
>>>>>
>>>>> However, the following issues were encountered:
>>>>> 1. After using DEMTracker to track geometry, even if I don't add any
>>>>> motion, the geometry will continue to drop down. How can I fix the
>>>>> geometry?
>>>>> 2. How to achieve the composite rotational motion mentioned above?
>>>>>
>>>>> Best regards,
>>>>> Wenxuan Xu
>>>>>
>>>>
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