Finding the position directly behind a player

[wolfknight]

I'm attempting SCIENCE by using math that I have never used before, nor do I understand (despite reading numerous articles, watching all of the khanacademy videos, etc etc)

I'm attempting to use trig to locate a point directly behind another player in Minecraft.
I've read through these three pages:
http://stackoverflow.com/questions/...rotational-axis-and-a-direction-calculate-end
http://en.wikipedia.org/wiki/Spherical_coordinate_system#Cartesian_coordinates
http://www.opentk.com/node/2505

and have come up with this code:

double dEntityDistance = getPlayer().getDistanceToEntity(player);
		
double dNewX = /* The current player */getPlayer().posX  - dEntityDistance * Math.sin(Math.toRadians(/* The player we want the position behind */ player.rotationYaw % 360)) * Math.cos(Math.toRadians(-player.rotationPitch));

double dNewZ = getPlayer().posZ - dEntityDistance * Math.cos(Math.toRadians(player.rotationYaw % 360)) * Math.cos(Math.toRadians(-player.rotationPitch));

I know nothing about matrices (which some have suggested), nor do I know very much about trig. If anybody would be kind enough to explain a bit about those two subjects (or whichever one would help me with my problem), I would be very grateful.

 

[mfb]

Behind relative to what? The plane, or the direction the player is looking to?
As a first step: Do you understand how Minecraft stores the orientation of the player? The definition of those parameters should give you a direct way to calculate x,y,z in front of the player. Behind is just the same, but with opposite signs for the distance.

Comments directly in formulas? Really?

 

[wolfknight]

the direction the player is looking to?

The direction the player is facing, yes, I apologize for not clarifying.

As a first step: Do you understand how Minecraft stores the orientation of the player?

I've been trying to find out for the last couple days. Notch and Jeb do it in a really really bad way, which is why I've been having loads of trouble.

Comments directly in formulas? Really?

Actually no, it's just that I was clarifying which entity was which.

 

[wolfknight]

I fixed this. Minecraft rotations are completely back-asswards, and it took me a while, but I now can successfully teleport behind other players.