How to scale a 3DAR point view with distance from user

gistfile1.m

// This code belongs in a custom point/marker view class.

// 
// Calculate this view's size scale based on distance from user's current location.
//
- (CGFloat) rangeScale 
{
    CGFloat scale = 1.0;
    
    if (self.poi)
    {
        CGFloat poiDistance = [self.poi distanceInMetersFromCurrentLocation];
        CGFloat minRange = 0.0;
        CGFloat maxRange = 10000.0;
        CGFloat minScaleFactor = 0.1;
        
        if (poiDistance > maxRange || poiDistance < minRange) 
        {
            scale = minScaleFactor;		
        } 
        else 
        {
            CGFloat scaleFactor = 1.0;		
            CGFloat rangeU = (poiDistance - minRange) / (maxRange - minRange);		
            scale = scaleFactor * (1.0 - ((1.0 - minScaleFactor) * rangeU));
        }	
    }    
    
    return scale;
}


// 
// A point view's pointTransform is automatically applied for each visible point.
//
- (CGAffineTransform) pointTransform 
{
    CGFloat scale = [self rangeScale];
    return CGAffineTransformMakeScale(scale, scale);
}