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Votes
3
Found in
2018.3.0a5
2019.1.12f1
2019.2.0a1
2019.3.0a1
2020.1.0a1
Issue ID
1181054
Regression
No
Rigidbody with "Continuous Speculative" produces different results when changing IsKinematic and the moving object is fast
How to reproduce:
1. Open attached project "Kinematic_Speculative.zip" and scene "SampleScene"
2. Enter Play mode and observe how many Cubes does the Bullet hit
3. Exit Play mode
4. In Hiearachy window, select "Bullet" object
5. In Inspector window, "Rigidbody" component -> change "Is Kinematic" to false
6. Repeat step 2
Expected result: only the middle cube is hit
Actual result: with "Is Kinematic" set to true there are more than 1 hit cube
Reproducible with: 2018.3.0a5, 2018.4.8f1, 2019.2.4f1, 2019.3.0b2, 2020.1.0a3
Not reproducible with: 2017.4.32f1, 2018.3.0a4
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Resolution Note:
False positives is the normal behaviour of the speculative collision detection in PhysX because all it does is inflates the contact offsets when the collisions start being detected proportionally to the linear and angular velocities. You see the difference dynamic vs kinematic here because dynamic is being teleported via transform essentially while the kinematic is driven by a kinematic goal that leads to the computation of high velocities => higher inflation that results in more false positives in the end. See PhysX code here: https://github.com/NVIDIAGameWorks/PhysX/blob/ae80dede0546d652040ae6260a810e53e20a06fa/physx/source/simulationcontroller/src/ScBodySim.cpp#L216