protected void ComputeProjections(
List <SSObject> objects,
Matrix4 cameraView,
Matrix4 cameraProj,
float fov, float aspect, float cameraNearZ, float cameraFarZ)
{
if (m_light.GetType() != typeof(SSDirectionalLight))
{
throw new NotSupportedException();
}
SSDirectionalLight dirLight = (SSDirectionalLight)m_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
);
// Step 0: camera projection matrix (nearZ and farZ modified) for each frustum split
float prevFarZ = cameraNearZ;
for (int i = 0; i < c_numberOfSplits; ++i)
{
// generate frustum splits using Practical Split Scheme (GPU Gems 3, 10.2.1)
float iRatio = (float)(i + 1) / (float)c_numberOfSplits;
float cLog = cameraNearZ * (float)Math.Pow(cameraFarZ / cameraNearZ, iRatio);
float cUni = cameraNearZ + (cameraFarZ - cameraNearZ) * iRatio;
float nextFarZ = LogVsLinearSplitFactor * cLog + (1f - LogVsLinearSplitFactor) * cUni;
float nextNearZ = prevFarZ;
// exported to the shader
m_viewSplits [i] = nextFarZ;
// create a view proj matrix with the nearZ, farZ values for the current split
m_frustumViewProjMatrices[i] = cameraView
* Matrix4.CreatePerspectiveFieldOfView(fov, aspect, nextNearZ, nextFarZ);
// create light-aligned AABBs of frustums
m_frustumLightBB [i] = SSAABB.FromFrustum(ref lightTransform, ref m_frustumViewProjMatrices [i]);
prevFarZ = nextFarZ;
}
#if true
// Optional scene-dependent optimization
for (int i = 0; i < c_numberOfSplits; ++i)
{
m_objsLightBB[i] = new SSAABB(float.PositiveInfinity, float.NegativeInfinity);
m_splitFrustums[i] = new SSFrustumCuller(ref m_frustumViewProjMatrices[i]);
m_shrink[i] = false;
}
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
{
for (int i = 0; i < c_numberOfSplits; ++i)
{
if (m_splitFrustums[i].isSphereInsideFrustum(obj.worldBoundingSphere))
{
// determine AABB in light coordinates of the objects so far
m_shrink[i] = true;
Vector3 lightAlignedPos = Vector3.Transform(obj.worldBoundingSphereCenter, lightTransform);
Vector3 rad = new Vector3(obj.worldBoundingSphereRadius);
Vector3 localMin = lightAlignedPos - rad;
Vector3 localMax = lightAlignedPos + rad;
m_objsLightBB[i].UpdateMin(localMin);
m_objsLightBB[i].UpdateMax(localMax);
}
}
}
}
#endif
for (int i = 0; i < c_numberOfSplits; ++i)
{
if (m_shrink [i])
{
m_resultLightBB[i].Min = Vector3.ComponentMax(m_frustumLightBB [i].Min,
m_objsLightBB [i].Min);
m_resultLightBB [i].Max = Vector3.ComponentMin(m_frustumLightBB [i].Max,
m_objsLightBB [i].Max);
}
else
{
m_resultLightBB [i] = m_frustumLightBB [i];
}
}
for (int i = 0; i < c_numberOfSplits; ++i)
{
// Obtain view + projection + crop matrix, need it later
Matrix4 shadowView, shadowProj;
viewProjFromLightAlignedBB(ref m_resultLightBB [i], ref lightTransform, ref lightY,
out shadowView, out shadowProj);
m_shadowViewProjMatrices[i] = shadowView * shadowProj * c_cropMatrices[i];
// obtain view + projection + clio + bias
m_shadowViewProjBiasMatrices[i] = m_shadowViewProjMatrices[i] * c_biasMatrix;
// There is, currently, no mathematically derived solution to how much Poisson spread scaling
// you need for each split. Current improvisation combines 1) increasing spread for the near
// splits; reducing spread for the far splits and 2) reducing spread for splits with larger
// light-aligned areas; increasing spread for splits with smaller light-aligned areas
m_poissonScaling [i] = m_resultLightBB [i].Diff().Xy / (100f * (float)Math.Pow(3.0, i - 1));
}
// Combine all splits' BB into one and extend it to include shadow casters closer to light
SSAABB castersLightBB = new SSAABB(float.PositiveInfinity, float.NegativeInfinity);
for (int i = 0; i < c_numberOfSplits; ++i)
{
castersLightBB.Combine(ref m_resultLightBB [i]);
}
// extend Z of the AABB to cover shadow-casters closer to the light
foreach (var obj in objects)
{
if (obj.renderState.toBeDeleted || obj.localBoundingSphereRadius <= 0f ||
!obj.renderState.visible || !obj.renderState.castsShadow)
{
continue;
}
else
{
Vector3 lightAlignedPos = Vector3.Transform(obj.worldBoundingSphereCenter, lightTransform);
Vector3 rad = new Vector3(obj.worldBoundingSphereRadius);
Vector3 localMin = lightAlignedPos - rad;
Vector3 localMax = lightAlignedPos + rad;
if (localMin.Z < castersLightBB.Min.Z)
{
if (OpenTKHelper.RectsOverlap(castersLightBB.Min.Xy,
castersLightBB.Max.Xy,
localMin.Xy,
localMax.Xy))
{
castersLightBB.Min.Z = localMin.Z;
}
}
}
}
// Generate frustum culler from the BB extended towards light to include shadow casters
Matrix4 frustumView, frustumProj;
viewProjFromLightAlignedBB(ref castersLightBB, ref lightTransform, ref lightY,
out frustumView, out frustumProj);
Matrix4 frustumMatrix = frustumView * frustumProj;
FrustumCuller = new SSFrustumCuller(ref frustumMatrix);
}
