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math, math, math

Started by The Kid Jan 14, 2001 at 1:13 PM 5 replies 400+ views

Original Post

Jan 14, 2001 at 1:13 PM

Okay peoples, here''s my problem, I hope you can help. I have a program that loades a ship from a model, and I can use the keys to rotate it. I use the keys to rotate the world around the model. But when it come to moving the world, thats where I get lost. When I press a key, I want the ship to have the illusion of moving forward, (actually moving the terrain backwards). But when the world rotates around the ship, I can''t just modify the z coordinates on the terrain, because it looks like the ship is sliding sideways. How could I make the terrain move in the right direction, so it looks like the ship is moving forward, instead of sideways. Thanks in advance. The Kid I don''''t know what the future holds, but I know who holds the future.

Elixer

Jan 14, 2001 at 2:20 PM

Are you using a matrix for rotations/translations, or gl calls? Do you have 4DOF or 6 or ??

rileyriley

Jan 14, 2001 at 4:02 PM

Have you tried translating before rotating? That is, modifying the z coordinates before you rotate the world around the ship?

/riley

The Kid

Author

The Kid

Jan 14, 2001 at 5:09 PM

Elixer - I''m only using 4DOF, and I''m using glCalls. Matrix transformations are a little difficult for me now.

But I''m learning.

rileyriley - whether I modify the z axis before or after I rotate the world, it still isn''t going to change the ships location on the x axis correctly. Thats what I''m having problems with. Thanks anyway, though.

The Kid

I don''''t know what the future holds, but I know who holds the future.

Bad Monkey

Jan 14, 2001 at 11:50 PM

It''s just some simple trig to make your ship move in the direction it is facing:

shipZ = shipZ + (movementDistance * cos(shipHeadingAngle))
shipX = shipX + (movementDistance * sin(shipHeadingAngle))

Similarly, to move backward, turn the + signs into - signs.
Strafing is a little more involved, but I''m sure you can work it out if you need it later...

NOTE: You may have to tinker with the sign of the Z value you get from this (depending on what handed coord system you are working in for your world coords).
Also, this is locked in the XZ plane... you can modify/add to it to include movement in the Y direction as well (invloves using the pitch angle of the ship as well).

Hope that helps a bit

avianRR

Jan 15, 2001 at 1:37 AM

Not to sound like an idiot (but I probably will anyway!)
I only know of 3 degrees of freedom ,Yaw, Pitch and Roll.
What would the others be in eather 4 or 6DOF ???

Quantum

Jan 15, 2001 at 1:53 AM

quote:
Original post by avianRR

Not to sound like an idiot (but I probably will anyway!)
I only know of 3 degrees of freedom ,Yaw, Pitch and Roll.
What would the others be in eather 4 or 6DOF ???

6DOF = Movement on X, Y, Z & Rotation on X, Y, Z.
4DOF would probably be the same minus one axis.

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