/*****************************************************************************
 *
 * Author: Andy Zupko 
 * http://blog.zupko.info
 * 
 * Write me if you use this for anything cool!
 *
 *****************************************************************************/

kernel Spotlight
{
   
    parameter float radius 
    <       
        minValue:float(0.1);
        maxValue:float(2000.0); 
        defaultValue:float(200.0);
    >;
    
     parameter float intensity
    <       
        minValue:float(0.1);
        maxValue:float(4.0); 
        defaultValue:float(2.0);
    >;
    
    parameter float lightSize
     <       
        minValue:float(0.1);
        maxValue:float(100.0); 
        defaultValue:float(4.0);
    >;

    parameter float2 center
    <
        minValue:float2(0.0, 0.0);
        maxValue:float2(2048.0, 2048.0);
        defaultValue:float2(256.0, 256.0);
    >;
    parameter float4 colors
    <
        minValue:float4(0.1, 0.1, 0.1, 0.1);
        maxValue:float4(2.1, 2.1, 2.1, 2.1);
        defaultValue:float4(1.0, 1.0, 1.0, 1.0);
    >;
    void evaluatePixel(image4 oImage, out float4 outputColor)
    {
        float2 relativePos = outCoord()-center;
        //get distance from center   
        float distFromCenter = length( relativePos );
        
        //get the "shade percent"
        float per = (distFromCenter < lightSize) ? intensity : intensity-((distFromCenter-lightSize)/radius);
       
        float4 shade = float4(per*colors.r, per*colors.g, per*colors.b, 1.0);
        
        //return new shaded pixel
        outputColor = shade*sampleNearest(oImage, outCoord());
        
    }
}