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    MSPhysics tests and questions

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    • F Offline
      faust07
      last edited by

      I could not resist to render a new desktop background picture for my PC ...
      MSPhysics, indigo RT (path tracing, 7 minutes), removal of the fire flies with image editor.


      SketchUp model


      relevant physics geometry


      SketchUp materials


      rendering indigo RT

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      • pilouP Offline
        pilou
        last edited by

        Happy Feet! 😎

        Frenchy Pilou
        Is beautiful that please without concept!
        My Little site :)

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        • F Offline
          faust07
          last edited by

          Test model as an example for large replay data stored in the MSPhysics 0.9.2 separate replay file.
          The data are produced with onTouch and transforming various emitters to the touch points.
          This principle is useful for other physics applications: tire tracks, landslides etc.
          The advantage over the Particle effect is, that you can render it.
          Please let the simulation run till frame 500 or longer, save Replay, exit the model, load it again and test what happens.


          file without birds and sharks


          pure SketchUp


          the target

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          • F Offline
            faust07
            last edited by

            Anton, here a long time me nagging question:
            How can I prevent that usually at the beginning of a simulation, transmitted Thruster objects rather accidentally fly into the air at an increased rate?
            This initial speed exceeds the set Thruster impulse by several times and can lead to problems with the viewport.
            Properties of the initial object are: non collidable, collision shape: Null, Thruster Controller: 30, Lock to Body Axis, Mass: 0.015
            Also setting the non-collision per script at the start does not work (onStart { this.collidable=(false) }).
            What is the reason for and what can I do to avoid this?
            Thanks in advance!


            Thruster on start of simulation


            randomly another start

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            • M Offline
              markahon
              last edited by

              How can I use joints or some other way to combine two or more groups/components to form a stiff structure so, that each will have different weight/density and the combined object's center of mass is correct?

              My specific problem is that I'm designing a table that has wooden tabletop and steel legs. I'm testing different kinds of steel structures as the legs. Then I'm placing weights on the edges of the table to get some kind of an idea what weight would cause the table to tip over and modify the legs' positioning if needed.

              I tried different kinds of joints, but they all seem to make the table to stand no matter what kind of weight I put on the table edge. The only way working so far for me is to use no joints at all, make the whole table a single component and set approximate weight that I calculate myself. But that will cause the center of mass to be incorrect and afaik affects the results of this simulation somwhat.

              Any help is much appriecated, thanks!

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              • M Offline
                markahon
                last edited by

                Edit: Duplicate post, see my question in next post.

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                • F Offline
                  faust07
                  last edited by

                  Please post your model (reduced, without textures, scenes, stiles etc.) and we will find a solution.

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                  • M Offline
                    markahon
                    last edited by

                    Thanks for the reply faust07. Here's one of my designs, reduced, I hope πŸ˜„ Table design to test what weights cause table to tip over

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                    • F Offline
                      faust07
                      last edited by

                      In this case it seems to be the right approach to take all the parts into a component.
                      Joints are possible but not very helpful here. (You could test it with the "Fixed" Joint)
                      What I've changed:
                      Table legs and feet broken down into individual subcomponents. Then the collision geometry is more accurate. You can see it if you activate Collision Wireframe in Debug Draw in the MSPhysics UI.
                      The base plate I have assigned the material Concrete and I have the axis position of the cube weights corrected in order to prevent that the parts sink into the ground.
                      The axes were far outside the cube. But I do not know whether this significantly affect the behaviour of the body.
                      The best way to prevent sinking is to increase the value for the material thickness (to 0.10) in the UI. Please test it.


                      table with little corrections

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                      • F Offline
                        faust07
                        last edited by

                        Hi Anton, short question: how can I make up for the differences between controller and scripted input? With the same pre-set parameters why arise the differences in the results?
                        Model slightly reduced to test it.


                        Pengu-Test_03.gif


                        Pengu-Test_03.skp

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                        • F Offline
                          faust07
                          last edited by

                          Here is an approximation of the setting of a servo joint (oscillator) with controller or script.
                          The oscillation about 180Β° in both directions corresponds to the number pi in the script. Seems somehow to be logical ...


                          Servo-Test_04.jpg


                          Servo-Test_04.skp

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                          • A Offline
                            Anton_S
                            last edited by

                            Hello faust,

                            Nice coding there. So, when you assign value via script, i.e some_servo.controller=, the value is assumed as some angle in radians. Whenever, you assign it via controller, the angle is assumed as the angle in preset angle units, which are by default in degrees.

                            Now, instead of iterating through all servos to assign their controller, a more reliable way would be to use a variable. Control the variable through script and change servo angle via controller. Here is what I mean:

                            onStart { @p3_head_osc = 30 set_var('wing', 0) } onUpdate { set_var('wing', oscillator(@p3_head_osc) * 30) }

                            Paste this in the controller of a desired servo:
                            get_var('wing')

                            Other than that, I'm amazed by your improvement in scripting. Keep it up!

                            Anton

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                            • F Offline
                              faust07
                              last edited by

                              Thanks Anton! The simple way is the best - I will try it. Here a little pengu fun with my old script solution and "Curvy Piston".


                              Pengu-Test_11.gif

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                              • robintR Offline
                                robint
                                last edited by

                                Hi All

                                Not wishing to hijack this OP, but I cant see where to post otherwise
                                so here goes. Attached is a simple falling block assy to test the validity of accel due to gravity, ie block should fall 9.81m in 1 sec, all thing set right.

                                What would be nice is to have a script that stopped the sim once the bloack collided with the baseplate. In theory I should be able to read the time taken, no of frames etc on the bottom lhs of the screen, but just now I approximate this by tapping pause on eyeballing the block - not very accurate at all

                                Iv'e seen there is an "on touch" script with slamming doors but Im still a ruby newbie

                                Is there a way to stop the sim on block reaching the baseplate?

                                FYI If I can get this to work for my students, then the next step is to simulate the viscosity experiment using a falling sphere in fluid, but I dont know if SU can simulate viscous fluid yet?

                                Great stuff on this page, I am truly humbled

                                Robin


                                falling block.skp

                                As one door closes another one slams in your face

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                                • F Offline
                                  faust07
                                  last edited by

                                  Hi Robint
                                  Put this script into your baseplate (copy the 3 lines, select the plate, open MSP UI, select "Script", paste the lines into the Script window, run MSP):

                                  onTouch { |toucher, position, normal|
                                  MSPhysics::Simulation.reset
                                  }

                                  and the simulation stops "onTouch".

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                                  • robintR Offline
                                    robint
                                    last edited by

                                    @faust07 said:

                                    Hi Robint
                                    Put this script into your baseplate (copy the 3 lines, select the plate, open MSP UI, select "Script", paste the lines into the Script window, run MSP):

                                    onTouch { |toucher, position, normal|
                                    MSPhysics::Simulation.reset
                                    }

                                    and the simulation stops "onTouch".

                                    Hi Faust, thanx for the tip, but not quite there yeet

                                    the simulation resets and I lose all the time/frame data at the bottom of screen - which is what I need for this to be useful.

                                    I tried .pause and .stop but they dont exist

                                    Is there something else I could try?

                                    As one door closes another one slams in your face

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                                    • robintR Offline
                                      robint
                                      last edited by

                                      Hi Faust

                                      Through the Ruby Code editor, I found a start_timer and stop_timer function

                                      Would this help?

                                      Say put start at the top to activate when staring sim,

                                      then stop_timer after the reset action line

                                      then display timer?

                                      sorry my newbie attempts at script (do you hav any recommendations on the best way to learn script for MSP - there's so much flack out there its hard to know where to start)

                                      Cheers

                                      Robin

                                      As one door closes another one slams in your face

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                                      • F Offline
                                        faust07
                                        last edited by

                                        Hi Robin,
                                        have tested to find a solution to pause simulation per script, but have nothing found until now.
                                        I'm a script newbie too. For my purposes I look into scripts of models from the experts at 3D-Warehouse (AntonS & PituPhysics) or ask them in Anton's main MSP post.

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                                        • robintR Offline
                                          robint
                                          last edited by

                                          Well we are both struggling, blind leading the blind

                                          FYI this timer thing is fundamental to simulating physical systems (mass speed acceleration)

                                          The on touch is a good start, just need to time the sequence and display result on reset

                                          opens up a whole new way of simulating mechanical systems

                                          as fundamental say as a thermometer is to tell you the temperature - if you see my point

                                          so I must perservere. If I get a result I will post it you

                                          Cheers

                                          Robin

                                          As one door closes another one slams in your face

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                                          • robintR Offline
                                            robint
                                            last edited by

                                            A bing moment has occured β˜€

                                            when I # out the reset line, I just had a ontouch line only and it outputs to screen what might be some sort of final velocity m/s on impact (according to the script info)

                                            pls see model

                                            Now I cant yet correlate that to the calc velocity which should be 14m/s on impact from 10m
                                            it comes out at 58 and varies with the UI sim setting of Newton update rate (currently 10)

                                            also from dropping from 5m gives 33 (should be 9.9m/s and is 1/sqr2 - .707) whereas 33/58 is ca.57

                                            maybe some dynamic friction in play?

                                            Is this a worthwhile line of enquiry?

                                            Cheers

                                            Robin

                                            ps the ball is in anton's examples funny little thing - and something for gamers pool table maybe?


                                            falling block.skp

                                            As one door closes another one slams in your face

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