I'm trying to detect when a player bumps their head on a ceiling or object above them when they jump, so I can reduce z_move to 0, so rather than being stuck on the ceiling for a bit before gravity pulls them down, they'll fall immediatly. I'm currently doing this with a c_trace, but because that's a line, it's inaccurate, and it's also a "Slow" command (which I think should be fine, but perhaps there's another way). I'm thinking I should use a c_scan so no matter what part of the player's head touches the ceiling, it will reduce z_move to 0, but that's also a "Slow" command, and I feel like c_scan would be a lot slower than c_trace. Is there another way to accomplish this? I'm willing to use c_scan, I'm just not sure if that's very efficient.

"Slow" and "fast" are relative terms. Neither of them will cause instructions to take a noticeable amount of time to execute, as long as they're not used excessively. So while you wouldn't want to be performing 500 long box traces each cycle, 50 short ones would be just fine. (I haven't stress tested that function so I don't know what the hard limits are, but basically use the "slow" functions sparingly and you'll be fine)

As for your question: c_scan() will only detect entities, not level geometry, so I wouldn't suggest you use that (unless your levels are made out of models). I would suggest you use a c_trace instruction in combination with the USE_BOX flag to perform a box trace upwards. That will accurately detect all surfaces above the "head" of your entity.

c_move(...)
if(HIT_TARGET && target.z > my.z+my.max_z*0.75) //you may not need the factor *0.75
{
my.speed_z = minv(my.speed_z,0);
}

To avoid this make sure you use c_move() for the movement and include a check for getting stuck by a collision in the while() condition.
It would look something like this:


A note on c_move from the manuall to clarify what "result" is being used for:


Hope this helps.

If you need a more detailed explanation head on to the other thread you created regarding jump height and time_step.
You might have missed it, but while answering your previous question yesterday I thought this "floating" might be your next problem with jumps, so i adressed both problems in that thread with a more extense step-by-step explanation:
http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=381979&page=2

This works well, but whenever less than half of the player entity hits the ceiling, he continues to stay floating, most likely because of the ellipsoid collision system being used when hitting blocks.

@Carlos3DGS:
Wow, I missed your reply on my previous thread. That actually makes a lot of sense! Currently my jump system doesn't work quite like that, but I think I'll try re-coding it. Thanks!

There is a problem with Carlos3DGS' solution, you have no actual jumping curve and thus the jump will feel unnatural and not smooth. Additionally, when the ceiling's surface is not orthogonal to the z-axis, your player will probably slide along the ceiling because of the GLIDE option and it's upwards movement won't be stopped (because then result > 0).


Then either remove my.max_z or decrease the factor.

Huh, you make a good point. The curve is very important. I solved my previous problem with your code. Because of how my collision box is set, I simply had to use min_z rather than max_z. Now it works perfectly! Thanks.

Glad that it works for you, but you should not use min_z. Otherwise, the jump will stop even if you touch a vertical wall or a step or the like. You can keep min_z but then you should check if (normal.z < -0.2) is true, that means if you hit a wall that is pointing down.

Seems to work fine at the moment. I must have a really odd jumping system then. But I added in the normal.z part just in case. Thank you, once again.

I'm wondering, could this also be used to check if the player is on the ground? How would the code look? I've played around with it, but I can't seem to get it to work.