  # rever

Member

65

## Community Reputation

122 Neutral

• Rank
Member
1. hey, i was trying to get this to work on my own but i ran into problems with roll and yaw..... considering a right hand system(x+ coming out, y pos going right , z positive going up). I did a rotation between the y and z axis, i got the following x"=x' y"=y'*cos(pitch)-z'*sin(pitch) z"=y'*sin(pitch)+z'*cos(pitch) which is fine. then i tried to project the same idea ont the other axis, and it seems to me that x'=z*sin(yaw)+x*cos(yaw) y'=y z'=z*cos(yaw)-x*sin(yaw) the above equations should be reversed. the z should be x and vice versa. The reasoning i am using here is that if we take a look at xz plane, then we can assume Z to be the vertical axis and x the horizontal axis, then the same principle applies as in the one above where z was the verticla axis and y the horizontal...but that measn that cos and sin should be reversed and the sign should be +ve.... Where did i go wronge in my reasoning?
2. Hello. I was doing some 3d trig and i noticed some diffrence in the way the planes are represented. Some have z plane going in and out of the page, but other have z going up and done the page and x going in and out...why the diffrence? And which one is mostly used? Thx
3. well.....just ....WOW. I got the answer in one of the books i got but this is a much better explanation that the book gave. Thx.Apriciate it.
4. hey, just a side note question? Is Euler's angle actually developed by Euler? or was it just named after him for some reason or another? Cuz i read some stuff while i was researchign the method and didn;t see the angle meantioned there but alot of other stuff was....
5. thx alot, i found a great explanation when i did a search fr Euler;s angle.
6. thx alot, i found a great explanation when i did a search fr Euler;s angle.
7. Hey. I have been reading the following article: http://www.gamedev.net/reference/articles/article790.asp and i understand most of it except: x'=z*sin(yaw)+x*cos(yaw) y'=y z'=z*cos(yaw)-x*sin(yaw) x"=x' y"=y'*cos(pitch)-z'*sin(pitch) z"=y'*sin(pitch)+z'*cos(pitch) x"'=y"*sin(roll)+x"*cos(roll) y"'=y"*cos(roll)-x"*sin(roll) z"'=z" I was wondering if somone can explain the concept of rotation of one of the plains. x'=z*sin(yaw)+x*cos(yaw) y'=y z'=z*cos(yaw)-x*sin(yaw) I understand why the y in kept the same but why is x calcualated as it is? I am trying to figure it out with trig but dind;t get far yet. Thx Alot.
8. thx alot for that:D
9. so this should increase the precision by some small and prolly insignificant degree on the gravity simulation?
10. actually that was for a general case that had nothing to do with circular orbits but rather motion of an objecet when thrown up.
11. (dLastVelocity+dAcceleration*0.5*dTime)->First time calculation (dLastVelocity+dAcceleration*dTime)-> All other times. I am pretty sure this is correct as i found this in a binder from a physics class.... Why do i need a 0.5 for the first calculation?
12. Hello. I was looking at eulers implementation and i see that i have a 0.5 the first time i calculate the velocit, and this is becuase i am taking the average velocity between the initial time and time+timestep, and i need to use 0.5 for the first time i calculate the velocity. Is that correct?If not why do i need a 0.5 to calculate the velocity first time? Thx
13. thx...... but can momentum be negative? i do the cross produc and i get a few negative numbers....because of the velocties...
14. what about the momentum of the sun, it is really small value but it keeps chanign on me.... is that normal? btw if i flip the sign then i get negative momentum....that is impossible....