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Comments:
<0> blahtex >> texvc and does MathML as well as better PNG rendering, better parsing and better everything else, pretty much, but it's going to take a little while to overcome the inertia of texvc
<1> what is texvc?
<0> the program wikipedia currently uses to process <math>...</math> elements
<1> presumably some kind of wrapper around tex or something?
<0> it's a TeX mathematics parser and renderer. it's what turns your math tags into PNG, for example.
<2> I have two points (x,y,z), points A and B, I am located at point A, I need the Pitch and Yaw to look directly at point B.
<2> How can I get the Pitch and Yaw?
<1> probably from the vector AB
<3> yep
<2> how do I get the vector AB?
<2> multiply A * B?
<3> on the other hand wth is pitch and yaw ? :)
<2> rotation? :P
<1> afaik theya re just angles of the vector AB with some of the axes
<3> Scottc : are you kidding ? AB=B-A
<2> and what do I do with B-A?
<2> er AB
<3> _llll_ : that what i was kinda guessing
<1> first find the defnition of pitch and yaw
<3> and then use AB :)
<1> i tihnk pitch is angle "above" the positive x-axis, and yaw is with the positive y-axis,
<4> Scottc: it's stupid notation. By default, we call the line that joins a point A and point B, "AB"
<4> Scottc: the vector is called "AB" - as one word
<0> @yaw
<5> I want to kill everyone here with a cute colorful Hydrogen Bomb!!
<3> oh
<3> you read AB as A*B ? that didn't even occur to me
<2> So B - A = my angle that I want?
<3> Catfive : computing a hydrogen bomb ?
<3> no
<4> Scottc: no, B-A gives you the vector of the line from point A to point B
<1> how is B-A a vector?
<3> B-A is the vector AB
<1> argh
<2> How do I turn that into an angle?
<1> how is B-A an angle?
<1> i think you need to read a basic tex on vectors here
<2> I agree
<1> is this for a program?
<3> Scottc : well vectors have angles with other vectors or planes
<2> yea
<2> i'm working on a 3D game with C++ and I need to make a turret look at its target.
<1> yeah, dont try and program by "trying stuff until it seems to work", first learn the mathematics of vectors, at least basic stuff
<1> then yor program will be much better
<3> _llll_ : so it is like the angles oh sphere coordinates ?
<2> I prefer to learn as I go... learn what I need
<4> Scottc: http://en.wikipedia.org/wiki/Trigonometric_function
<4> Scottc: Look at that
<4> Scottc: look at the second picture - Right angle definitions
<4> Scottc: you have your points A and B just like that picture, right?
<1> kmh: i think so, i think when you fly a plane you use the joystick to control pitch/roll/yaw, which are the 3 angles in some order
<4> _llll_: plus you have gimbal lock and fun like that ;)
<3> _llll_ : why 3 and not 2 ?
<1> i may be completely wrong of course
<4> _llll_: which you need to understand
<1> well, cos it's in 3d?
<1> what is gimbal lock?
<3> yes
<3> but sphere coordinates have 2 angles + radius
<4> _llll_: if you are at point A and looking at point B, then where is your "up" direction?
<4> _llll_: you tend to just say the up direction is up
<0> http://wikipedia.org/wiki/Flight_dynamics
<1> oh, well the 3 things are the angles with the 3 axes. i tihnk
<4> _llll_: but then when you look straight up, there's no clear "up" direction for your picture anymore
<4> _llll_: hence gimbal lock
<3> hmmm that's different though
<1> perhaps sphere coordinates is the wrong word
<3> or to put it this way for the turret to look the right direction you would need only 2 angles
<3> independent of the flight stick thing
<2> how would I get those angles ?
<4> kmh: consider those two angles. now consider looking straight up
<4> kmh: can you see there's a problem?
<3> no
<2> are you trying to explain gimbal lock?
<3> what are you talking about now
<3> steering is different from just looking in the right direction
<4> Scottc: did you look at that diagram
<1> i dont follow this gimbal stuff
<2> I did johnflux
<3> and a turret wouldn't rotate
<3> ouch
<4> Scottc: so if you know where A and B, that diagram shows you how to get that angle
<3> i mean a turret doesn't roll
<3> it just rotates in 2 direction (yaw & pict i guess)
<4> imagine you point the turret West
<4> then point it upwards and upwards
<4> until it's point straight up
<2> with cos and sin, johnflux?
<4> Scottc: right
<4> kmh: now consider instead, you point the turret East
<2> cos and sin take angles in radians though
<4> kmh: and then point it up until it points straight up
<2> in programming
<4> kmh: can you see that the end result will be different
<2> so I guess I need the opposite of cos and sin?
<2> whats the opposite of cos and sin?
<3> JohnFlux_ : either way 2 angles are enough for the turret
<4> kmh: if you are just firing, sure
<3> exactly
<4> kmh: if you want to "look" that way (like in a computer game) then you have a problem
<3> the turret is stationary
<4> Scottc: 1 radian / PI * 180 = 1 degree
<2> JohnFlux
<2> sin and cos don't return radians
<3> JohnFlux_ : i'm not sure what you mean by looking
<4> Scottc: if you have x = cos() then acos(x) =
<2> ah
<4> same for tan and atan
<4> and sin and asin
<3> http://en.wikipedia.org/wiki/Image:Spherical_Coordinates.png
<3> P is your B and A is the origin
<2> I wonder if acos requires me to normalize the value...
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