/**
* EvaluateSubBlock
* Iterates over all pixels in the specified rectangle, if the resulting pixel
* isn't black, mid grey or would result in X or Y being -1 or +1 then it is
* added to the average color and the number of samples count is incremented.
*/
void EvaluateSubBlock( int32 Left, int32 Top, int32 Width, int32 Height )
{
for ( int32 Y=Top; Y != (Top+Height); Y++ )
{
for ( int32 X=Left; X != (Left+Width); X++ )
{
FLinearColor ColorSample = Sampler.DoSampleColor( X, Y );
// Nearly black or transparent pixels don't contribute to the calculation
if (FMath::IsNearlyZero(ColorSample.A, AlphaComponentNearlyZeroThreshold) ||
ColorSample.IsAlmostBlack())
{
continue;
}
// Scale and bias, if required, to get a signed vector
float Vx = Sampler.ScaleAndBiasComponent( ColorSample.R );
float Vy = Sampler.ScaleAndBiasComponent( ColorSample.G );
float Vz = Sampler.ScaleAndBiasComponent( ColorSample.B );
const float Length = FMath::Sqrt(Vx * Vx + Vy * Vy + Vz * Vz);
if (Length < ColorComponentNearlyZeroThreshold)
{
// mid-grey pixels representing (0,0,0) are also not considered as they may be used to denote unused areas
continue;
}
// If the vector is sufficiently different in length from a unit vector, consider it invalid.
if (FMath::Abs(Length - 1.0f) > NormalVectorUnitLengthDeltaThreshold)
{
NumSamplesRejected++;
continue;
}
// If the vector is pointing backwards then it is an invalid sample, so consider it invalid
if (Vz < 0.0f)
{
NumSamplesRejected++;
continue;
}
AverageColor += ColorSample;
NumSamplesTaken++;
}
}
}
/**
* EvaluateSubBlock
* Iterates over all pixels in the specified rectangle, if the resulting pixel
* isn't black, mid grey or would result in X or Y being -1 or +1 then it is
* added to the average color and the number of samples count is incremented.
*/
void EvaluateSubBlock( int32 Left, int32 Top, int32 Width, int32 Height )
{
for ( int32 Y=Top; Y != (Top+Height); Y++ )
{
for ( int32 X=Left; X != (Left+Width); X++ )
{
FLinearColor ColorSample = Sampler.DoSampleColor( X, Y );
if ( !ColorSample.IsAlmostBlack() )
{
if (FMath::IsNearlyZero(ColorSample.A, AlphaComponentNearlyZeroThreshold))
{
AverageColor += FLinearColor::Transparent;
NumSamplesTaken++;
continue;
}
// Scale and bias, if required, to get a signed vector
float Vx = Sampler.ScaleAndBiasComponent( ColorSample.R );
float Vy = Sampler.ScaleAndBiasComponent( ColorSample.G );
float Vz = Sampler.ScaleAndBiasComponent( ColorSample.B );
// If the vector is close to zero (mid-gray) then ignore it as invalid
if ( FMath::IsNearlyZero(Vx, ColorComponentNearlyZeroThreshold) &&
FMath::IsNearlyZero(Vy, ColorComponentNearlyZeroThreshold) &&
FMath::IsNearlyZero(Vz, ColorComponentNearlyZeroThreshold) )
{
continue;
}
// Assume that if X or Y are very close to +1 or -1 then it is an invalid sample.
// If this were to happen in a real normal map, it would imply an impossible gradient
if ( !FMath::IsWithinInclusive( Vx, ColorComponentMinVectorThreshold, ColorComponentMaxVectorThreshold ) ||
!FMath::IsWithinInclusive( Vy, ColorComponentMinVectorThreshold, ColorComponentMaxVectorThreshold ) )
{
continue;
}
AverageColor += ColorSample;
NumSamplesTaken++;
}
}
}
}