Method UpdateSubSurfaceFrontScatterData

trinity/Tr2SSSSS.cpp:187–268

}

void Tr2SSSSS::UpdateSubSurfaceFrontScatterData( Tr2RenderContext& renderContext )
{

	// FUTUREWORK this will be exposed via a "quality" setting
	const int nSamples = 17;
	std::array<Vector4, nSamples> kernel;

	// Update front scattering kernal
	{


		const float RANGE = nSamples > 20 ? 3.0f : 2.0f;
		const float EXPONENT = 2.0f;


		// Calculate the offsets
		float step = 2.0f * RANGE / ( nSamples - 1 );
		for( int i = 0; i < nSamples; i++ )
		{
			float o = -RANGE + float( i ) * step;
			float sign = o < 0.0f ? -1.0f : 1.0f;
			kernel[i].w = RANGE * sign * abs( pow( o, EXPONENT ) ) / pow( RANGE, EXPONENT );
		}

		// Calculate the weights
		for( int i = 0; i < nSamples; i++ )
		{
			float w0 = i > 0 ? abs( kernel[i].w - kernel[i - 1].w ) : 0.0f;
			float w1 = i < nSamples - 1 ? abs( kernel[i].w - kernel[i + 1].w ) : 0.0f;
			float area = ( w0 + w1 ) / 2.0f;
			Vector3 t = profile( kernel[i].w ) * area;
			kernel[i].x = t.x;
			kernel[i].y = t.y;
			kernel[i].z = t.z;
		}


		// We want the offset 0.0 to come first
		Vector4 t = kernel[nSamples / 2];
		for( int i = nSamples / 2; i > 0; i-- )
			kernel[i] = kernel[i - 1];
		kernel[0] = t;


		// Calculate the sum of the weights, we will need to normalize them below
		Vector3 sum = Vector3( 0.0f, 0.0f, 0.0f );
		for( int i = 0; i < nSamples; i++ )
		{
			sum += Vector3( kernel[i].x, kernel[i].y, kernel[i].z );
		}

		// Normalize the weights
		for( int i = 0; i < nSamples; i++ )
		{
			kernel[i].x /= sum.x;
			kernel[i].y /= sum.y;
			kernel[i].z /= sum.z;
		}