[osg-users] [Re: to draw landscapes beginning from a matrix]

[aurora restivo]

Hi!

if I use a ShapeDrawable I get a figure with an only color, because 
"draw -> setColor (...)" it doesn't allow me to color every altitude

    osg::Geode* geode= new osg::Geode();
    osg::ShapeDrawable* draw= new osg::ShapeDrawable(hF);
    double highColor=1.0;
    double lowColor=0.2;

    double R=0.0, G=0.0, B=0.0;
   
        for(int i=0; i< 410; i++)
            {
                for(int j=0; j<296 ;j++)
                {
                    float altitude = hF->getHeight(j,i);

                    R =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;
                    G =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;
                    B =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;

                    draw->setColor(osg::Vec4(R,G,B,1.0));           
                }
            }   
   
    geode->addDrawable(draw);


if I draw a TerrainNode with GeometryTechnique and use
terrainNode - > setColorTransferFunction (0, tf.get());
I get a figure with an only color if I use "tf -> allocate (1);"
otherwise, if I use "tf -> allocate (2);" I get a colored figure to two 
zones, etc...

osg::ref_ptr<osg::TransferFunction1D> tf = new osg::TransferFunction1D;
        tf->setInputRange(min, max); //minAltitude = 0, maxAltitude = 1400
        tf->allocate(1);
       //or    tf->allocate(2);

        for(int i=0; i< 410; i++)
           {
               for(int j=0; j<296 ;j++)
               {
                   float altitude = hF->getHeight(j,i);

                   R =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;
                   G =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;
                   B =(highColor - lowColor) * ((altitude - min) / max) 
+ lowColor;

                   tf->setValue(0, osg::Vec4(R,G,B,1.0));
                   //tf->setValue(1, osg::Vec4(1.0,0.0,1.0,1.0));
                   terrainNode->setColorTransferFunction(0, tf.get());
                  
               }
           }

how can I color every altitude with different color?
I apologize for the trouble
Thanks
Aurora




Vincent Bourdier ha scritto:
> Hi Aurora,
>
> With his proposition, you can create the color that you need.
> Setcolor(vec4) uses RGBA (Red, Green, Blue, Alpha) color (if i 
> remember well) so put A to 1.0 (opacity) , and the RGB can be defined 
> using the function he gives to you... you can use it for each 
> component if you want a greyscale color (R=G=B) or only use it on one 
> component... try it and you will see...
>
> for greyscale image, you can try :
>
> hightcolor = 1.0
> lowcolor = 0.0
>
> and then
>
> R =(highColor - lowColor) * ((altitude - minAltitude) / maxAltitude) + 
> lowColor;
> G =(highColor - lowColor) * ((altitude - minAltitude) / maxAltitude) + 
> lowColor;
> B =(highColor - lowColor) * ((altitude - minAltitude) / maxAltitude) + 
> lowColor;
>
> this is just a simple example...
>
> Regards,
>
> Vincent.
>
> 2008/2/29, aurora restivo <aurora_re at tiscali.it 
> <mailto:aurora_re at tiscali.it>>:
>
>     The Sukender ha scritto:
>>     Hum... I don't have a global solution, but you may set a color for each vertex with something lile :
>>     color = (highColor - lowColor) * ((altitude - minAltitude) / maxAltitude) + lowColor;
>>       
>
>
>
>     I apologize but I am still inexperienced.
>
>     I have a HeightField associated to shapeDrawable (this because if
>     I use Locator and GeometryTechnique I succeed in visualizing the
>     alone ground "GEOCENTRIC"),
>     therefore if I use
>
>     shapeDrawable - > setColor (Vec4);
>
>     I don't know whether to plan the values of the Vec4 with the
>     formula that you have sent me
>
>     besides of what type it is color?
>
>     Aurora
>
>
>
>>     You can allso do it in HSL coordinates (instead of RGB).
>>
>>     Sukender
>>
>>     ----------------------------------------
>>       
>>>     Date: Fri, 29 Feb 2008 12:54:48 +0100
>>>     From: aurora_re at tiscali.it <mailto:aurora_re at tiscali.it>
>>>     To: osg-users at lists.openscenegraph.org <mailto:osg-users at lists.openscenegraph.org>
>>>
>>>     Subject: Re: [osg-users] [Fwd: Re: to draw landscapes beginning from a	matrix]
>>>
>>>     Hi!
>>>
>>>     does a way exists to color from the tallest altitude of a ground to the 
>>>     lowest with gradations of color?
>>>
>>>     thanks
>>>
>>>     Aurora
>>>
>>>             
>

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