private void ComputeProjections(List <SSObject> objects,
SSLightBase light,
Matrix4 cameraView, Matrix4 cameraProj)
{
if (light.GetType() != typeof(SSDirectionalLight))
{
throw new NotSupportedException();
}
SSDirectionalLight dirLight = (SSDirectionalLight)light;
// light-aligned unit vectors
Vector3 lightZ = dirLight.Direction.Normalized();
Vector3 lightX, lightY;
OpenTKHelper.TwoPerpAxes(lightZ, out lightX, out lightY);
// transform matrix from regular space into light aligned space
Matrix4 lightTransform = new Matrix4(
lightX.X, lightX.Y, lightX.Z, 0f,
lightY.X, lightY.Y, lightY.Z, 0f,
lightZ.X, lightZ.Y, lightZ.Z, 0f,
0f, 0f, 0f, 0f
);
// Find AABB of frustum corners in light coordinates
Matrix4 cameraViewProj = cameraView * cameraProj;
SSAABB frustumLightBB = SSAABB.FromFrustum(ref lightTransform, ref cameraViewProj);
bool shrink = false;
SSAABB objsLightBB = new SSAABB(float.PositiveInfinity, float.NegativeInfinity);
#if true
// (optional) scene dependent optimization
// Trim the light-bounding box by the shadow receivers (only in light-space x,y,maxz)
FrustumCuller cameraFrustum = new FrustumCuller(ref cameraViewProj);
foreach (var obj in objects)
{
// pass through all shadow casters and receivers
if (obj.renderState.toBeDeleted || obj.localBoundingSphereRadius <= 0f ||
!obj.renderState.visible || !obj.renderState.receivesShadows)
{
continue;
}
else if (cameraFrustum.isSphereInsideFrustum(obj.worldBoundingSphere))
{
// determine AABB in light coordinates of the objects so far
shrink = true;
Vector3 lightAlignedPos = Vector3.Transform(obj.worldBoundingSphereCenter, lightTransform);
Vector3 rad = new Vector3(obj.worldBoundingSphereRadius);
Vector3 localMin = lightAlignedPos - rad;
Vector3 localMax = lightAlignedPos + rad;
objsLightBB.UpdateMin(localMin);
objsLightBB.UpdateMax(localMax);
}
}
#endif
// Optimize the light-frustum-projection bounding box by the object-bounding-box
SSAABB resultLightBB = new SSAABB(float.PositiveInfinity, float.NegativeInfinity);
if (shrink)
{
// shrink the XY & far-Z coordinates..
resultLightBB.Min.Xy = Vector2.ComponentMax(frustumLightBB.Min.Xy, objsLightBB.Min.Xy);
resultLightBB.Min.Z = objsLightBB.Min.Z;
resultLightBB.Max = Vector3.ComponentMin(frustumLightBB.Max, objsLightBB.Max);
}
else
{
resultLightBB = frustumLightBB;
}
// View and projection matrices, used by the scene later
viewProjFromLightAlignedBB(ref resultLightBB, ref lightTransform, ref lightY,
out m_shadowViewMatrix, out m_shadowProjMatrix);
// Now extend Z of the result AABB to cover shadow-casters closer to the light inside the
// original box
foreach (var obj in objects)
{
if (obj.renderState.toBeDeleted || obj.localBoundingSphereRadius <= 0f ||
!obj.renderState.visible || !obj.renderState.castsShadow)
{
continue;
}
Vector3 lightAlignedPos = Vector3.Transform(obj.worldBoundingSphereCenter, lightTransform);
Vector3 rad = new Vector3(obj.worldBoundingSphereRadius);
Vector3 localMin = lightAlignedPos - rad;
if (localMin.Z < resultLightBB.Min.Z)
{
Vector3 localMax = lightAlignedPos + rad;
if (OpenTKHelper.RectsOverlap(resultLightBB.Min.Xy,
resultLightBB.Max.Xy,
localMin.Xy,
localMax.Xy))
{
resultLightBB.Min.Z = localMin.Z;
}
}
}
// Generate frustum culler from the BB extended towards light to include shadow casters
Matrix4 frustumView, frustumProj;
viewProjFromLightAlignedBB(ref resultLightBB, ref lightTransform, ref lightY,
out frustumView, out frustumProj);
Matrix4 frustumMatrix = frustumView * frustumProj;
FrustumCuller = new FrustumCuller(ref frustumMatrix);
}
