ODE 2d Pixel coordinates

ODE is unitless. You can, in theory, choose any units you want for length, time, mass, and as long as the values you assign for mass/inertia tensor, forces, torques, etc., are consistent, it will work. So...you could choose your length unit to be a pixel. And if you choose to use SI units for everything else you'd have to specify your values something like:

mass = kg
length = pixel
time = second
density = kg / (pixel³)
force = kg-pixel/(second²)
velocity = pixel/second
acceleration = pixel/(second²)
torque = kg-(pixel²)/(second²)

They key.....is consistency. If you let pixels be your length unit, you cannot mix-and-match with meters or anything else. Your force values, torque values, everything will have to be built on pixels. But, it can be done with ODE proper.

One other thing you'll have to look out for, potentially. When dealing with values that have very different magnitudes, say 0.000001 and 1x10²⁸, it is easy to lose precision when doing floating point math. For example, 1x10²⁸ minus 0.000001 will yield exactly 1x10²⁸ because there aren't enough bits to represent the full precision result. This can cause difficulties that are difficult to trace. And when you play around with different units types, types that may be very different from real-world units, you may very well exaggerate the precision problem.

Thanks :), I will try that.