/// <summary>
/// Renders the shadow map using the orthographic camera created in
/// CalculateFrustum.
/// </summary>
protected void renderShadowMap(RenderPrimitives renderDelegate, int splitIndex)
{
// Set the viewport for the current split
Viewport splitViewport = new Viewport();
splitViewport.MinZ = 0;
splitViewport.MaxZ = 1;
splitViewport.Width = ShadowMapSize;
splitViewport.Height = ShadowMapSize;
splitViewport.X = splitIndex * ShadowMapSize;
splitViewport.Y = 0;
context.Rasterizer.SetViewports(splitViewport);
renderDelegate(lightCameras[splitIndex]);
}
/// <summary>
/// Renders a list of models to the shadow map, and returns a surface
/// containing the shadow occlusion factor
/// </summary>
/// <param name="modelList">The list of models to render</param>
/// <param name="depthTexture">Texture containing depth for the scene</param>
/// <param name="light">The light for which the shadow is being calculated</param>
/// <param name="mainCamera">The camera viewing the scene containing the light</param>
/// <returns>The shadow occlusion texture</returns>
public void UpdateShadowMap(RenderPrimitives renderDelegate, DirectionalLight light, ICamera mainCamera)
{
context.ClearDepthStencilView(shadowMapDsv, DepthStencilClearFlags.Depth, 1, 0);
context.ClearState();
context.OutputMerger.SetTargets(shadowMapDsv);
// Get corners of the main camera's bounding frustum
Matrix cameraTransform, viewMatrix;
viewMatrix = mainCamera.View;
cameraTransform = Matrix.Invert(viewMatrix);
BoundingFrustum frustum = new BoundingFrustum(mainCamera.ViewProjection);
frustum.GetCorners(frustumCornersWS);
Vector3.TransformCoordinate(frustumCornersWS, ref viewMatrix, frustumCornersVS);
for (int i = 0; i < 4; i++)
{
farFrustumCornersVS[i] = frustumCornersVS[i + 4];
}
// Calculate the cascade splits. We calculate these so that each successive
// split is larger than the previous, giving the closest split the most amount
// of shadow detail.
float N = NumSplits;
float near = mainCamera.NearClip, far = mainCamera.FarClip;
splitDepths[0] = near;
splitDepths[NumSplits] = far;
const float splitConstant = 0.95f;
for (int i = 1; i < splitDepths.Length - 1; i++)
{
splitDepths[i] = splitConstant * near * (float)Math.Pow(far / near, i / N) + (1.0f - splitConstant) * ((near + (i / N)) * (far - near));
}
// Render our scene geometry to each split of the cascade
for (int i = 0; i < NumSplits; i++)
{
float minZ = splitDepths[i];
float maxZ = splitDepths[i + 1];
lightCameras[i] = CalculateFrustum(light, mainCamera, minZ, maxZ);
renderShadowMap(renderDelegate, i);
}
// We'll use these clip planes to determine which split a pixel belongs to
for (int i = 0; i < NumSplits; i++)
{
lightClipPlanes[i].X = -splitDepths[i];
lightClipPlanes[i].Y = -splitDepths[i + 1];
lightViewProjectionMatrices[i] = lightCameras[i].ViewProjection;
//lightProjectionMatrices[i] = lightCameras[i].Projection;
//lightCameras[ i ].GetViewProjMatrix( out );
}
}
