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dForce behaves completely different depending on graphics card

mx90209mx90209 Posts: 69
edited March 2019 in Daz Studio Discussion

Under the simulation "Advanced" settings, you change your OpenCL device if you have more than one card/compatible CPU. I have three options and I tried them all. Turns out, ven though all the other settings remain unchanged, a simple simulation of a pane hitting a slanted surface behaves COMPLETELY different depending on which openCL device you use. See the screenshot, showing frame 92 of this simulation on 3 different OpenCL devices - no other setting was changed whatsoever! Note also that this is not the simulations having run for different lenghts - the Frames To Simulate setting is set to "Animated" so all three are run the same way. In addition, by frame 93, the Intel ones had stopped moving while the Nvidia pane was still sliding.

I assumed things would be faster by switching to a Nvidia GPU, but I didn't think the nature of the simulation itself would be so heavily impacted.

Is this a bug or a feature? How can we trust dforce-ready products to work as advertised when the simulation is this system-dependent?

dforcecomparison.jpg
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Post edited by mx90209 on

Comments

  • TheKDTheKD Posts: 2,696

    Try running the same sim more than once on the same device. Maybe it will come out slightly different every time you run a sim, even on the same device.

  • mx90209mx90209 Posts: 69
    edited April 2019

    I had attached a picture to the original post, was it deleted by the mods for any reason (no PM, so I can't tell)? Or a forum bug? Re-posting it.

    EDIT( removed, it's displaying in the OP for now again, odd)

    EDIT2: It's not displaying in the OP again, re-adding it here.

    dforcecomparison.jpg
    2871 x 1011 - 163K
    Post edited by mx90209 on
  • mx90209mx90209 Posts: 69
    TheKD said:

    Try running the same sim more than once on the same device. Maybe it will come out slightly different every time you run a sim, even on the same device.

    No, they come out (probably exactly) the same when I re-run them on the corresponding devices, actually.

  • ParadigmParadigm Posts: 421

    If we're accepting hearsay I can attest to noticing this same phenomenon. I have a 2080TI in my PC and a 1070 in my laptop. Both using the same version of the beta. I was rendering a a scene where I had a woman holding up a shirt to display to another woman and on my 1070 it would hit her fingers... sit there for a while and then turn into a blob of spikes. On my 2080TI it draped fine.

    I kind of wonder if it has anything to do with the time it takes to go to the next step, because the only difference I can notice is that the 2080 steps through more quickly. On a surface level I wouldn't think it would matter but maybe there's some sort of randomness that changes based on time? idk just taking shots in the dark.

  • Richard HaseltineRichard Haseltine Posts: 102,344

    According to Rob the time isn't a factor, but differences in how the OpenCL instructions are handled, with diffrent shortcuts or optimisations affecting the output in smal ways that can have a large cumulative effect.

  • mx90209mx90209 Posts: 69
    edited April 2019
    Richard Haseltine said:

    According to Rob the time isn't a factor, but differences in how the OpenCL instructions are handled, with diffrent shortcuts or optimisations affecting the output in smal ways that can have a large cumulative effect.

    Who is Rob?

    Edit to fix quote attribution

    Post edited by Richard Haseltine on
  • ChoholeChohole Posts: 33,604
    edited April 2019
    mx90209 said:
    Richard Haseltine said:

    According to Rob the time isn't a factor, but differences in how the OpenCL instructions are handled, with diffrent shortcuts or optimisations affecting the output in smal ways that can have a large cumulative effect.

    Who is Rob?

     

    Post edited by Richard Haseltine on
  • ParadigmParadigm Posts: 421
    Chohole said:
    mx90209 said:
    Richard Haseltine said:
     

    The hairbender

  • ChoholeChohole Posts: 33,604
    edited April 2019
    Paradigm said:
    Chohole said:
    mx90209 said:
    Richard Haseltine said:
     

    The hairbender

    One of, if not the, longest serving members of the Daz staff, and also extremely knowledgable about all things Daz and DS.

    Post edited by Chohole on
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