nested for/while loops

Discussion in 'C++' started by ahso, Dec 4, 2011.

  1. ahso

    ahso Guest

    Hi
    a function returns Z (height) after giving X and Y location. How
    would those two for (or while?) loops look like if I need all z points
    in a rectangle.
    Many thanks
    Michael
     
    ahso, Dec 4, 2011
    #1
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  2. ahso

    ralph Guest

    On Sun, 4 Dec 2011 07:04:41 -0800 (PST), ahso <>
    wrote:

    >Hi
    > a function returns Z (height) after giving X and Y location. How
    >would those two for (or while?) loops look like if I need all z points
    >in a rectangle.
    >Many thanks
    >Michael


    I'm probably missing something as that question doesn't make any
    sense.

    Even assuming each "X" and "Y" describes a point. Everything else
    would be simple linear addition or substraction.

    Need more info.

    -ralph
     
    ralph, Dec 4, 2011
    #2
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  3. On Dec 4, 3:04 pm, ahso <> wrote:
    > Hi
    >  a function returns Z (height) after giving X and Y location. How
    > would those two for (or while?) loops look like if I need all z points
    > in a rectangle.
    > Many thanks
    > Michael


    you need to work out how X,Y gets turned into Z
     
    Nick Keighley, Dec 4, 2011
    #3
  4. On 12/4/2011 12:23 PM, Nick Keighley wrote:
    > On Dec 4, 3:04 pm, ahso<> wrote:
    >> Hi
    >> a function returns Z (height) after giving X and Y location. How
    >> would those two for (or while?) loops look like if I need all z points
    >> in a rectangle.
    >> Many thanks
    >> Michael

    >
    > you need to work out how X,Y gets turned into Z


    No, he needs to work out how "a rectangle" turns into X and Y.

    V
    --
    I do not respond to top-posted replies, please don't ask
     
    Victor Bazarov, Dec 4, 2011
    #4
  5. ahso

    ahso Guest

    Ok it's a little more complicated:
    ---
    Probes the terrain. Pass in the XYZ coordinate of the probe point...
    Other fields are filled in if we hit terrain, and a probe result
    * is returned.
    ----
    So i give that function x,y,z coordinates and if it hits terrain I get
    a result. Now I see why i only get a few points to draw as it hits
    around the viewer but loses ground contact in the mountains etc.
    I want to get the z (ground contact) within a 128x128 square around my
    position, for a heightmap. (color z in different colors)
    Many thanks indeed as I'm stuck...
    Regards Michael
     
    ahso, Dec 5, 2011
    #5
  6. ahso

    Werner Guest

    On Dec 5, 8:56 am, ahso <> wrote:


    > Many thanks indeed as I'm stuck...
    > Regards Michael


    Post some code...
     
    Werner, Dec 5, 2011
    #6
  7. ahso

    ahso Guest

    Getting closer, now I have lines from top left to bottom right:

    for( int x=0; x< 16384; x++ ){
    draw x,y,z

    I need also a y for loop?
    Thanks
    Michael
     
    ahso, Dec 5, 2011
    #7
  8. On 12/5/2011 9:19 AM, ahso wrote:
    > Getting closer, now I have lines from top left to bottom right:
    >
    > for( int x=0; x< 16384; x++ ){
    > draw x,y,z
    >
    > I need also a y for loop?
    > Thanks
    > Michael


    Michael,

    You need to sit down and write your algorithm with a pencil on a piece
    of paper. "I have lines from top left to bottom right" - what does that
    mean? We have no idea. It's not a description of an algorithm.
    Perhaps you need to think about the algorithm for a while. Perhaps you
    should also look into some *formality* in your activities. So far your
    posts indicate that your work is very hap-hazard. Step back from
    programming for an hour and think what actions you would take if you
    were the computer and you needed to accomplish whatever goal you're
    setting for it.

    To make tea, what do you need? You need a cup, water source, dry tea
    (loose or in a bag) and a way to heat the water to the boiling point.
    Water source is in the kitchen (or the bathroom). So, as part of the
    algorithm for making tea you need to ensure you're in one of those
    locations. To boil water you need some energy source. A microwave
    would do (make sure it's plugged into an electrical outlet). And so on.
    You write down preconditions, then you write down your actions. It
    becomes the algorithm for accomplishing your goal.

    Same thing with making calculations. Or drawing a shape. Or
    controlling a nuclear reactor. You need the algorithm first, THEN you
    can put it in terms of the language you've chosen to implement it.

    V
    --
    I do not respond to top-posted replies, please don't ask
     
    Victor Bazarov, Dec 5, 2011
    #8
  9. ahso

    ahso Guest

    Look for yourself, your comments are all sick...
     
    ahso, Dec 6, 2011
    #9
  10. ahso

    Ian Collins Guest

    On 12/ 6/11 08:07 PM, ahso wrote:
    > Look for yourself, your comments are all sick...


    Who should look? What comments?

    Don't snip context.

    --
    Ian Collins
     
    Ian Collins, Dec 6, 2011
    #10
  11. ahso

    Werner Guest

    On Dec 5, 4:19 pm, ahso <> wrote:
    > Getting closer, now I have lines from top left to bottom right:
    >
    >         for( int x=0; x< 16384; x++ ){
    > draw x,y,z
    >
    > I need also a y for loop?
    > Thanks
    > Michael


    Michael,

    What you have given us is not code... It
    is not even psuedo code.

    Function...

    Output [Appropriate Name] (All necessary input parameters).

    is already a start...

    Kind regards,

    Werner
     
    Werner, Dec 6, 2011
    #11
  12. On Dec 6, 7:07 am, ahso <> wrote:

    > Look for yourself, your comments are all sick...


    smart move. Ask for advice then criticise it...

    you said

    ****
    So i give that function x,y,z coordinates and if it hits terrain I
    get
    a result. Now I see why i only get a few points to draw as it hits
    around the viewer but loses ground contact in the mountains etc.
    I want to get the z (ground contact) within a 128x128 square around
    my
    position, for a heightmap. (color z in different colors)
    Many thanks indeed as I'm stuck...
    ***

    you really do nedd to sit down and think about the problem. What is a
    "rectangle"? What is "terrain". What is a "result"?

    also: viewer, ground contact, mountains, heightmap, color...

    you add new terminology faster tahn you generate sensible requirements

    to me this sounds like you might be taking a "slice" though the
    terrain. In general this will yield a series of closed curves. And
    then finding the point on one of these closed curves that is nearest
    to your X,Y position. but I'm doing a *lot* of guessing.
     
    Nick Keighley, Dec 6, 2011
    #12
  13. ahso

    ahso Guest

    now I did a vector[x/y][rgb]
    x or y and the color seems ok now how to draw this?

    for( int laty=0; laty< Terrain_Size; laty++ ){
    for( int lonx=0; lonx< Terrain_Size; lonx++ ){
    draw in opengl colored points
    }
    }
    doesn't obviously work. how should those for loops look like?
    Thanks
     
    ahso, Dec 6, 2011
    #13
  14. "ahso" wrote in message
    news:...
    >
    >now I did a vector[x/y][rgb]
    >x or y and the color seems ok now how to draw this?
    >
    >for( int laty=0; laty< Terrain_Size; laty++ ){
    > for( int lonx=0; lonx< Terrain_Size; lonx++ ){
    >draw in opengl colored points
    >}
    >}
    >doesn't obviously work. how should those for loops look like?
    >Thanks


    I don't understand your "obviously". Can you explain why it doesn't work?
     
    Fred Zwarts \(KVI\), Dec 6, 2011
    #14
  15. On 12/6/2011 8:02 AM, ahso wrote:
    > now I did a vector[x/y][rgb]
    > x or y and the color seems ok now how to draw this?
    >
    > for( int laty=0; laty< Terrain_Size; laty++ ){
    > for( int lonx=0; lonx< Terrain_Size; lonx++ ){
    > draw in opengl colored points
    > }
    > }
    > doesn't obviously work.


    "Obviously"?... Well, yes, the

    draw in opengl colored points

    is not C++ code (unless those are names of some macros that, when
    substituted, produce compilable C++ code). Try replacing it with, say,

    printf("point: %d %d\n", laty, lonx);

    and see if it "works" then.

    > how should those for loops look like?


    The loops look OK, *given* certain assumptions. But my assumptions can
    be totally different from yours. State yours, and we can verify.

    Also visit: http://catb.org/~esr/faqs/smart-questions.html and
    http://www.parashift.com/c -faq-lite/how-to-post.html

    V
    --
    I do not respond to top-posted replies, please don't ask
     
    Victor Bazarov, Dec 6, 2011
    #15
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