How to calculate motion from distance and height

[Colened]

I want an entity to draw a trajectory and move 5 blocks horizontally and 4 blocks vertically in a direction where a player is looking in the end.

I have tried below, but the entity moved further and higher.

Vector3d vector = player.getLookVec().normalize().mul(5, 1, 5);
entity.setMotion(vector.x, 4, vector.z);

How can I derive the motion from desired distance and height?

[ChampionAsh5357]

There's a difference between velocity and distance. First, you normalize the look vector. This means that the vector will be anywhere from 0-1. Also, when you multiply it by 5, you are moving 5x more in the direction you were looking. Also, the motion upward will be 4. This is the velocity of the object (which is the distance per unit of time). So, based on the time unit used by Minecraft, in the first time unit, the user will move 5x the normalized look vector and 4 upwards. Their motion will continue in that direction for a parabolic curve of some kind depending on the motion calculated.

So, basically, just do physics.

[Colened]

25 minutes ago, ChampionAsh5357 said:

So, basically, just do physics.

Do you know how the velocity changes over time?

I found this table on the wiki but I do not get how to interpret those values.

[ChampionAsh5357]

29 minutes ago, Colened said:

Do you know how the velocity changes over time?

That's physics once again. You should really look over Newton's Laws of Motion to understand that. As for Minecraft's specific case, I've never looked into it.

31 minutes ago, Colened said:

I found this table on the wiki but I do not get how to interpret those values.

Again physics. It even gives you the calculations. A player has a velocity of 3.92 blocks per every in-game tick. Their acceleration is 0.08 blocks per every in-game tick squared. This forum is not really a physics course. You should probably look up actual velocity, distance, and acceleration formulas, plug the values in, and adjust to get the values you want.

[Colened]

8 hours ago, ChampionAsh5357 said:

You should probably look up actual velocity, distance, and acceleration formulas, plug the values in, and adjust to get the values you want.

I do know this is related to projectile motion.

With trials and errors, I found that a vector of length 1.1 and an angle of 50 degrees almost result in what I want but when I plug those values in v^2 * sin(2 * θ) / g (as noted here) where v = 1.1, θ = 50 / 180 * 3.14 and g = 0.08, its result is larger than how much an entity moves in the game. I wanted to know if there is a specific equation that Minecraft uses or what are the values that Minecraft uses in the projectile motion not to be lectured for physics.

[ChampionAsh5357]

2 hours ago, Colened said:

or what are the values that Minecraft uses in the projectile motion not to be lectured for physics

Apologies, not trying to lecture you. I just assume that the person I'm talking to only knows enough information in Java and not anything else. Only reason I mention it is that it's how any game calculates physics.

 

If I remember correctly, the entity's motion in the x and z every tick is multiplied by 0.91 and the slipperiness of the block underneath if the entity is on the ground. For the y direction, it's motion should be the y motion minus the effect of gravity (by default 0.08) and multiplied by 0.98f.

[Draco18s]

Due to air resistance*

I hate that it's baked in as a hardcoded value and not labeled in any way, but that's where the value comes from.

[Colened]

5 hours ago, ChampionAsh5357 said:

Apologies, not trying to lecture you.

I also apologize if I sounded rude.

5 hours ago, ChampionAsh5357 said:

If I remember correctly, the entity's motion in the x and z every tick is multiplied by 0.91 and the slipperiness of the block underneath if the entity is on the ground. For the y direction, it's motion should be the y motion minus the effect of gravity (by default 0.08) and multiplied by 0.98f.

5 hours ago, Draco18s said:

Due to air resistance*

Thank both of you. I guess I either have to try to come up with a quite complicated equation or just stick with trials and errors.

[Mortimer Kerman]

On 10/1/2020 at 6:01 AM, ChampionAsh5357 said:

If I remember correctly, the entity's motion in the x and z every tick is multiplied by 0.91 and the slipperiness of the block underneath if the entity is on the ground. For the y direction, it's motion should be the y motion minus the effect of gravity (by default 0.08) and multiplied by 0.98f.

Yeah, it's exactly this. I've used this in many of my projects, and it's working perfectly to change gravity strength and air resistance accurately.