Method SetupShadowSplit

trinity/Tr2ShadowMap.cpp:144–224

-------------------------------------------------------------------------------- Description: Go through all i count of frustum splits. Calculate the corresponding bounding box based on zNear and zFar values. --------------------------------------------------------------------------------

//	bounding box based on zNear and zFar values.
// --------------------------------------------------------------------------------
ShadowMap::SplitSetup Tr2ShadowMap::SetupShadowSplit( int splitIndex, Matrix invViewTransform, const Vector3 lightDirection, float zNear, float leftDivNear, float rightDivNear, float topDivNear, float bottomDivNear )
{
	CCP_STATS_ZONE( __FUNCTION__ );

	ShadowMap::SplitSetup splitSetup;

	if( splitIndex == 0 )
	{
		// reset this value
		m_oldZFar = zNear;
	}

	float zFar = m_splitValues[splitIndex];

	// to save some shader data mem we combine the zFar values into a float4 array of 4 so (x,y,z,w) are zFar values
	m_perSplitData.ShadowMapValues[splitIndex / 4][splitIndex % 4] = zFar;

	float left = leftDivNear * m_oldZFar;
	float right = rightDivNear * m_oldZFar;
	float top = topDivNear * m_oldZFar;
	float bottom = bottomDivNear * m_oldZFar;
	auto projection = PerspectiveOffCenterMatrix( left, right, bottom, top, m_oldZFar, zFar );

	m_oldZFar = zFar;

	// we can apply the inverse of the view and projection matrices on the corner points of the unit cube to get the frustum corners in world space
	splitSetup.invViewProj = Inverse( projection ) * invViewTransform;

	// Find light view
	Matrix lightView = Inverse( OrthoNormalBasisZ( -lightDirection ) );

	Vector3 corners[8];

	AxisAlignedBoundingBox aabb = CalculateAABB( projection, invViewTransform, lightView, corners );

	// Snap the projection in texel-sized increments to avoid crawling shadows on still objects
	if( m_disableShimmer )
	{
		// find max dist
		float maxDist = 0.0;

		// First take the farthest corners of our camera view projection
		// subtract them, get the length of the results and divide by 2 to get the radius
		for( unsigned int i = 0; i < 8; ++i )
		{
			// length between i and j is the same as between j and i so let's skip that comparison
			for( unsigned int j = i + 1; j < 8; ++j )
			{
				// longest dist between 2 corners
				maxDist = std::max( maxDist, Length( corners[i] - corners[j] ) );
			}
		}
		float radius = std::ceil( maxDist / 2.0f );
		Vector3 shipPos = Vector3( 0.0, 0.0, 0.0 );
		Vector3 center = aabb.Center();
		// rounding up
		float texelSize = ( radius * 2.0f ) / m_size;
		center.x = std::floor( center.x / texelSize + 0.5f ) * texelSize;