void ComputeFrustum(float minZ, float maxZ, RenderView cameraRenderView, int split)
{
// Shorten the view frustum according to the shadow view distance
Matrix cameraMatrix = cameraRenderView.GetWorldMatrix();
Vector4 camPos = cameraRenderView.GetEyePosShader();
for (int i = 0; i < 4; i++)
splitFrustumCornersVS[i] = frustumCornersVS[i + 4] * (minZ / camPos.W);
for (int i = 4; i < 8; i++)
splitFrustumCornersVS[i] = frustumCornersVS[i] * (maxZ / camPos.W);
Vector3.Transform(splitFrustumCornersVS, ref cameraMatrix, frustumCornersWS);
// Position the shadow-caster camera so that it's looking at the centroid,
// and backed up in the direction of the sunlight
BoundingBox sceneBounds = scene.GetSceneDimensions();
Vector3 sceneCenter = (sceneBounds.Min + sceneBounds.Max) * 0.5f;
Vector3 sceneExtents = (sceneBounds.Max - sceneBounds.Min) * 0.5f;
Vector3 lightDir = -this.Transformation.GetPosition();
lightDir.Normalize();
Matrix viewMatrix = Matrix.CreateLookAt(sceneCenter - (lightDir * sceneExtents.Length()), sceneCenter, new Vector3(0, 1, 0));
// Determine the position of the frustum corners in light space
Vector3.Transform(frustumCornersWS, ref viewMatrix, frustumCornersLS);
// Calculate an orthographic projection by sizing a bounding box
// to the frustum coordinates in light space
Vector3 mins = frustumCornersLS[0];
Vector3 maxes = frustumCornersLS[0];
for (int i = 0; i < 8; i++)
{
maxes = Vector3.Max(frustumCornersLS[i], maxes);
mins = Vector3.Min(frustumCornersLS[i], mins);
}
// Create an orthographic camera for use as a shadow caster
//const float nearClipOffset = 380.0f;
float nearPlane = -maxes.Z-sceneExtents.Length();
float farPlane = -mins.Z;
renderViews[split].SetPosition(viewMatrix.Translation);
renderViews[split].SetView(viewMatrix);
renderViews[split].SetNearPlane(nearPlane);
renderViews[split].SetFarPlane(farPlane);
renderViews[split].SetProjection(Matrix.CreateOrthographicOffCenter(mins.X, maxes.X, mins.Y, maxes.Y, nearPlane, farPlane));
lightViewProjectionMatrices[split] = renderViews[split].GetViewProjection();
lightClipPositions[split] = renderViews[split].GetEyePosShader();
}
