Laser Speedfinder

[NilsMolinder]

Right, so I've looked around in the forum and now I'm tired of looking (it's late).

I want to use a laser to set a variable to the velocity of an object (more specifically the X velocity) and I can't get it working. I tried a few variations of "scene.my.value = e.geom.velocity" on laser hit, but didn't work. I tried to make it read density the same way, which worked.
So now I'm asking, can anyone tell me how to make this work?
Also, is it possible to divide a value, something like "{scene.my.value}/10", for the length of a spring?

If you're curious, I want to make an automatic target finder for a cannon compensate for target speed. Got the rest of the target finder worked out.

[TC42]

You can't read the velocity with e.vel; you must use a longer script.

Go reverse-engineer Kilinich's K-probe. It should have a velocity reading script. If not, it isn't that hard to make your own... Then, you can call a script similar to the vel-reading script there when the laser hits the projectile. Ideally, you would have to attach a beacon to the projectile, but in this case you aren't allowed to... Yes, you can apply math to variables virtually anywhere--you could set the spring length to length = {sin(cos((sim.time/13)^87 - tan(scene.my.variable^3))/2)} --Just keep the whole thing in curly brackets. {scene.my.var}/10 will not work, it must be {scene.my.var / 10}.

[NilsMolinder]

Seems kinda like I have to use a script to determine the speed by reading the distance travelled within a certain time. Bothersome! xD
Edit: I have no idea what I just wrote above, I'm tired!
Anyways, I think I'm gonna delay this project until tomorrow when I've gotten some sleep and might be able to think properly.

Thanks for your help!

[bozbez]

Stick this in the laser's onLaserHit; laser must have maxrays=0, otherwise you'll get insane readings. scene.my.objvel is an array, so [1,0] would mean x velocity=1, and y=0:

Code: Select all

(e)=>{
    scene.my.varcr = sim.time - scene.my.vartm(2);
    (scene.my.varcr < 0.001) ? {scene.my.varcr = 0.001} : {};
    scene.my.objvel = [(e.pos(0) - scene.my.vartm(0)) / scene.my.varcr, (e.pos(1) - scene.my.vartm(1)) / (scene.my.varcr)];
    scene.my.vartm = [e.pos(0), e.pos(1), sim.time]
}

[Someone Else]

If you are like me and are okay with using an alternating collider, you can use this code (credit davidz40):

Code: Select all

textureMatrix = [(e.pos(0) - textureMatrix(2)) * 50, (e.pos(1) - textureMatrix(3)) * 50, e.pos(0), e.pos(1), 0, 0, 0, 0, 0];
scene.my.vel = [textureMatrix(0), textureMatrix(1)]

And yes, fooling around with pos, previous pos, and time delay are the only way to go. I say use an alternating collider because they output exactly 50 Hz, so you don't need to fool around with time and previous time.

Let me know if you don't know what an alternating collider is.