How does NEWXVALUE, NEWYVALUE, and NEWZVALUE work?

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2Beastmode4u

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Posted: 21st Jul 2011 23:04

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As the title says, how do these commands work?

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Rich Dersheimer

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Posted: 21st Jul 2011 23:30

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Well, the help files on them explain them pretty good, but basically, you start with a location, then get a new location by giving the command an angle and a distance.

If you are only doing 2D instead of 3D, then you only need to calculate a new x and z value. The y value is not used, it is replaced by the z value.

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2Beastmode4u

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Posted: 21st Jul 2011 23:38

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Yes, but what is the equation it uses? Is it some intersect thing?

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Rich Dersheimer

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Posted: 21st Jul 2011 23:53 Edited at: 21st Jul 2011 23:55

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Not sure what you mean.

Here's an example...

+ Code Snippet

set display mode 800,600,32

do
    cls
    input "How many sides? "; sides
    input "Radius? "; radius
    slice = 360.0/sides
    
    for x = 0 to sides-1
        angle1# = slice*x
        angle2# = slice*(x+1)
        x1 = newxvalue(400.0,angle1#,radius)
        y1 = newzvalue(300.0,angle1#,radius)
        x2 = newxvalue(400.0,angle2#,radius)
        y2 = newzvalue(300.0,angle2#,radius)                       
        line x1,y1,x2,y2
    next x
    
    wait key
loop

It's just an easy way to calculate new coordinates, without using COS or SIN. A typical use might be where you know what angle your spaceship is pointed, and you know what velocity your spaceship is moving. These commands would give you the next location of your ship.

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Van B

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Posted: 22nd Jul 2011 00:03

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It's often used when moving something, like a sprite - you'd pass the current sprite coordinates, angle, and distance to move.

Newxvalue(100.0,45.0,1.0)
Newyvalue(100.0,45.0,1.0)

is the same as:

100.0+(sin(45.0)*1.0)
100.0+(cos(45.0)*1.0)

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2Beastmode4u

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Posted: 22nd Jul 2011 01:53

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Thanks guys. That equation was just what I needed.

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Rich Dersheimer

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Posted: 22nd Jul 2011 14:18 Edited at: 22nd Jul 2011 14:19

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@ Van B - if we're talking about sprites, then shouldn't newyvalue be newzvalue? When going from 3D to 2D, the new z coordinate is used for the 2D y coordinate.

Thus

+ Code Snippet

sync on
sync rate 60
circle 32,32,31
line 32,32,32,0
line 22,22,32,0
line 42,22,32,0
get image 1,0,0,64,64,1
sprite 1,400,300,1
offset sprite 1,32,32

do
    if leftkey() then rotate sprite 1, wrapvalue(sprite angle(1)-1)
    if rightkey() then rotate sprite 1, wrapvalue(sprite angle(1)+1)
    if upkey()
        x = newxvalue(sprite x(1),sprite angle(1),5)
        y = NEWZVALUE(sprite y(1),sprite angle(1),-5)
        sprite 1,x,y,1
    endif
    sync
loop

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TheComet

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Posted: 22nd Jul 2011 14:21 Edited at: 22nd Jul 2011 14:22

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@ Rich Dersheimer

Correct. I'm not sure myself, but I think newyvalue does something like this:

y=newyvalue(100,45,1)

y=100+(sin(45-90)*1)

What do you need that for anyway? That command has been confuzzling me for a while now.

TheComet

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Gencheff

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Posted: 22nd Jul 2011 14:52

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TheComet,
Let's say I have a camera I can tilt up/down with the mouse and want it to zoom in/out with the scroll.

IF the scroll<0 then I'd use this to fix the camera's y position : newyvalue(camera position y(CurrentViewport),wrapvalue(camera angle x(CurrentViewport)),-5)
You could just use move camera instead though.

Samotnijat vylk nasred gorata.
-3D,2D Artist,Animator,Web developer and Programmer.

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2Beastmode4u

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Posted: 29th Jul 2011 21:28

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Quote: "What do you need that for anyway?"

Just for a script I was working on. Now I just need to know the equation for sin, cos, and tan.

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TheComet

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Posted: 29th Jul 2011 23:11

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Quote: "[quote]What do you need that for anyway?"

Just for a script I was working on. Now I just need to know the equation for sin, cos, and tan.[/quote]

I mean, what do you need newyvalue for anyway as a command, not why you need it

Equation for cos, sin, tan?

cos

a^2 = b^2 + c^2 - 2bc*cos(alpha)
b^2 = a^2 + c^2 - 2ac*cos(beta)
c^2 = a^2 + b^2 - 2ab*cos(gamma)

sin

a/sin(alpha) = b/sin(beta) = c/sin(gamma)

tan

I forgot

TheComet

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Dar13

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Posted: 30th Jul 2011 00:31

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tan(alpha) = sin(alpha) / cos(alpha)

Game Dev Blog

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2Beastmode4u

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Posted: 29th Aug 2011 00:40

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[Sorry for the bump]

So,

If I wanted to recreate the equations would they be this:

NEWXVALUE=
100.0+Current_X_Value(Equation for Sin*AngleValue)*1.0

NEWYVALUE=

100.0+Current_y_Value(Equation for Cos*AngleValue)*1.0

NEWZVALUE=

100.0+Current_y_Value(Equation for Tan*AngleValue)*1.0

I just an not sure what to put for the equations part. If anyone has an example, I'd be very great full.

Quote: "what do you need newyvalue for anyway as a command"

To set the camera of a 3D object.

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God help me, Please.

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Neuro Fuzzy

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Posted: 29th Aug 2011 04:29 Edited at: 29th Aug 2011 04:31

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To find the equation for cos() and sin()?

Well... There's a problem. Cosine and sine are non-algebraic functions. That means that they cannot be expressed in any finite sequence of + - * / or power operators. They are called transcendental functions, because they "transcend" algebra.

If you're interested in how the approximations work... check out taylor series. If you want an algebraic function that's a good approximation of cosine and sine, the wikipedia article on taylor series has one.

In short: use the cos() and sin() functions.

[edit]
also, I don't think you're going the right direction for whatever it is you want to solve. Could you elaborate on what you're trying to do?

Why does blue text appear every time you are near?

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Bluespark

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Posted: 29th Aug 2011 20:31 Edited at: 29th Aug 2011 20:33

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Taylor series are only good very near the points that they are centered at, for cos() and sin(). I found that you can get very accurate results by using the mod operation since cos() and sin() are periodic functions.

Also, based on this:

Quote: "NEWXVALUE=
100.0+Current_X_Value(Equation for Sin*AngleValue)*1.0

NEWYVALUE=

100.0+Current_y_Value(Equation for Cos*AngleValue)*1.0

NEWZVALUE=

100.0+Current_y_Value(Equation for Tan*AngleValue)*1.0"

I would say that TC is trying to rewrite the functions for newxvalue, newyvalue, newzvalue.
The way TC is doing is is not correct, as they do not replicate the new value commands. Rather, this seems to be an incorrect attempt to generalize polar movement from 2D to 3D.
The correct generalization is spherical movement, where the equations you want to use involve TWO angles and a length.

inc x#,R*sin(Theta)*cos(Phi)
inc y#,R*sin(Theta)*sin(Phi)
inc z#,R*cos(Theta)

In this case, R, Theta, and Phi are floats (you may want to declare them as such at the beginning of the program).

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basjak

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Posted: 30th Aug 2011 04:17

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how about this simple radar:

+ Code Snippet

centrex#=screen width()/2.0
centrey#=screen height()/2.0

ink rgb(0,255,0)

do
    cls
    for i#=0 to 360 step .5 
        cls
    
        radarscreen(centrex#,centrey#)  `radar
    
        ink rgb(255,255,255)
        x#=newxvalue(centrex#,i#,200)
        y#=newzvalue(centrey#,-i#,200)
        line centrex#,centrey#,x#,y#   `rotating line
        wait 5
    next
loop

end

function radarscreen(x#,y#)
    ink rgb(0,255,0)
    circle x#,y#,200
    circle x#,y#,50
    line x#-220,y#,x#+220,y#
    line x#,y#-220,x#,y#+220
ENDFUNCTION

or this one:

+ Code Snippet

centrex#=screen width()/2.0
centrey#=screen height()/2.0

ink rgb(rnd(255),rnd(255),rnd(255)),0

for i#=0 to 2500 step .2
    x#=newxvalue(centrex#,i#,i#/10.0)
    y#=newzvalue(centrey#,i#,i#/10.0)   
    
    circle x#+i,y#+i,5    
next

wait key
end

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DarkBASIC Professional Discussion / How does NEWXVALUE, NEWYVALUE, and NEWZVALUE work?