# How to convert STR to Initial Velocity

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Hello,

I am working on a sports engine and want to model an accurately interpreted trajectory calculation from an initial velocity and angle. I'm confident enough with the physics part of it. What I need a little help with is converting from STR to that Initial Velocity. Possibly parallel discussion around DEX-based (or combat scores, challenges, etc) around the Angles.

Couple of "real world" examples:

• QB throws pass with trajectory: Initial Velocity + Angle contributing to trajectory, the timing of which determines how long ball will be in flight, approximately where it should land, unless player intervenes (i.e. receives, deflects, intercepts, or falls incomplete).
• Kicker kicks punt with trajectory: Initial Velocity + Angle ... or kicks off ... or free kicks ... of attempts field goal.
• Pitcher attempts slider pitch across home plate ...
• Left Wing attempts slap shot at net ...

Anyway, you get the idea. Making the assumption we're dealing with Characteristics, Skills, and other traits, in a human realm; Characteristic scores may exceed 20, but we're not talking about superhuman scales here, only a better honed, better performing version of the same human.

If anyone had any insights into the HERO System itself, that would be helpful. Does not need to be precise, just a good starting point. Would help establish some basis, some precedent, at any rate.

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Sounds like the starting point should be a Throw. How far could the QB throw the football under the STR to distance rules? If that's the maximum distance, assume it's also the optimal distance-maximizing trajectory. Now go ahead and apply the physics in place of the usual Hero simplification that velocity doesn't vary and the object reaches the end point pretty much instantly.

Now, we probably also need to make special Maneuvers for Punt, Field Goal Kick, various Pitches (maybe great pitchers can even customize these to build their own maneuvers), slap shots (weapon element: hockey stick), etc.

Definitely meeting your "not precise" request, I'm afraid, but seems like a reasonable starting point.

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How far might be another question. Not how far, but how fast: initial velocity.

If I take the damage dice as a modifier, could start from a calibrated 42 MPH base (who knew? answer to life the universe and everything), then add in the damage roll as the resulting initial velocity, that seems to work out pretty well.

With a STR 20, 4d6, on average that's about 14; 42+14=56, which is right in the neighborhood of a pro QB throwing velocity.

Kickers are a little bit different calibration, same modifier, velocities can range anywhere into the 70 MPH range.

Doesn't need to be precise, just mechanically work out pretty well during simulation.

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"How Far" is simply a question of "how fast" for "how long".

You indicated you're ready to apply the physics, so I assumed you would be OK working out the trajectory, time and thus velocity (initial and at various stages of the throw). Of course, sports objects don't travel the full distance - the intent is often that someone catch them before then, or that they get stopped by the net after scoring.

We know "how far" from the throwing table (a Kick should add something to the distance as a maneuver - or a Punt might simply be a Haymaker). That seems like the most relevant starting point to me.

I'm unclear what you're planning on using it for - I had assumed there would be a need to determine starting velocity, distance travelled in a given time period (ie can I intercept it in that time) and, presumably, velocity at various points in the trajectory (so we know the velocity I have to catch it at), as well as points on that trajectory (for example, how high must I jump to catch it, especially relevant if we're catching a baseball headed for the wall and a home run).

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It's true, could solve for distance or velocity, depending on the starting point. The couple of trajectory models I am studying like to start from initial angles, velocities, and even incorporate rotation or spin, to help determine stability during flight.

Yes, timing will be worked out as players are moved around the field; i.e. if defender is within X amount of distance, say a meter or two, he could plausibly make an attempt to deflect, or even intercept, a pass.

Anyhow, thanks so much for the feedback, it's appreciated.

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I'll be interested to see any other suggestions, and what you eventually come up with.

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