protected override void OnProcess(RenderContext context)
{
context.ThrowIfCameraMissing();
context.ThrowIfGBuffer0Missing();
var graphicsDevice = GraphicsService.GraphicsDevice;
var renderTargetPool = GraphicsService.RenderTargetPool;
var source = context.SourceTexture;
var target = context.RenderTarget;
var viewport = context.Viewport;
// Get temporary render targets.
var sourceSize = new Vector2F(source.Width, source.Height);
var isFloatingPointFormat = TextureHelper.IsFloatingPointFormat(source.Format);
var sceneFormat = new RenderTargetFormat(source.Width, source.Height, false, source.Format, DepthFormat.None);
var maskedScene = renderTargetPool.Obtain2D(sceneFormat);
var rayFormat = new RenderTargetFormat(
Math.Max(1, (int)(sourceSize.X / DownsampleFactor)),
Math.Max(1, (int)(sourceSize.Y / DownsampleFactor)),
false,
source.Format,
DepthFormat.None);
var rayImage0 = renderTargetPool.Obtain2D(rayFormat);
var rayImage1 = renderTargetPool.Obtain2D(rayFormat);
// Get view and view-projection transforms.
var cameraNode = context.CameraNode;
Matrix44F projection = cameraNode.Camera.Projection.ToMatrix44F();
Matrix44F view = cameraNode.View;
Matrix44F viewProjection = projection * view;
// We simply place the light source "far away" in opposite light ray direction.
Vector4F lightPositionWorld = new Vector4F(-LightDirection * 10000, 1);
// Convert to clip space.
Vector4F lightPositionProj = viewProjection * lightPositionWorld;
Vector3F lightPositionClip = Vector4F.HomogeneousDivide(lightPositionProj);
// Convert from clip space [-1, 1] to texture space [0, 1].
Vector2 lightPosition = new Vector2(lightPositionClip.X * 0.5f + 0.5f, -lightPositionClip.Y * 0.5f + 0.5f);
// We use dot²(forward, -LightDirection) as a smooth S-shaped attenuation
// curve to reduce the god ray effect when we look orthogonal or away from the sun.
var lightDirectionView = view.TransformDirection(LightDirection);
float z = Math.Max(0, lightDirectionView.Z);
float attenuation = z * z;
// Common effect parameters.
_parameters0Parameter.SetValue(new Vector4(lightPosition.X, lightPosition.Y, LightRadius * LightRadius, Scale));
_parameters1Parameter.SetValue(new Vector2(Softness, graphicsDevice.Viewport.AspectRatio));
_intensityParameter.SetValue((Vector3)Intensity * attenuation);
_numberOfSamplesParameter.SetValue(NumberOfSamples);
_gBuffer0Parameter.SetValue(context.GBuffer0);
// First, create a scene image where occluders are black.
graphicsDevice.SetRenderTarget(maskedScene);
_viewportSizeParameter.SetValue(new Vector2(graphicsDevice.Viewport.Width, graphicsDevice.Viewport.Height));
_sourceTextureParameter.SetValue(source);
graphicsDevice.SamplerStates[0] = isFloatingPointFormat ? SamplerState.PointClamp : SamplerState.LinearClamp;
graphicsDevice.SamplerStates[1] = SamplerState.PointClamp; // G-Buffer 0.
_createMaskPass.Apply();
graphicsDevice.DrawFullScreenQuad();
// Downsample image.
context.SourceTexture = maskedScene;
context.RenderTarget = rayImage0;
context.Viewport = new Viewport(0, 0, rayImage0.Width, rayImage0.Height);
_downsampleFilter.Process(context);
// Compute light shafts.
_viewportSizeParameter.SetValue(new Vector2(context.Viewport.Width, context.Viewport.Height));
graphicsDevice.SamplerStates[0] = isFloatingPointFormat ? SamplerState.PointClamp : SamplerState.LinearClamp;
for (int i = 0; i < NumberOfPasses; i++)
{
graphicsDevice.SetRenderTarget(rayImage1);
_sourceTextureParameter.SetValue(rayImage0);
_blurPass.Apply();
graphicsDevice.DrawFullScreenQuad();
// Put the current result in variable rayImage0.
MathHelper.Swap(ref rayImage0, ref rayImage1);
}
// Combine light shaft image with scene.
graphicsDevice.SetRenderTarget(target);
graphicsDevice.Viewport = viewport;
_viewportSizeParameter.SetValue(new Vector2(graphicsDevice.Viewport.Width, graphicsDevice.Viewport.Height));
_sourceTextureParameter.SetValue(source);
_rayTextureParameter.SetValue(rayImage0);
graphicsDevice.SamplerStates[0] = isFloatingPointFormat ? SamplerState.PointClamp : SamplerState.LinearClamp;
graphicsDevice.SamplerStates[1] = isFloatingPointFormat ? SamplerState.PointClamp : SamplerState.LinearClamp;
_combinePass.Apply();
graphicsDevice.DrawFullScreenQuad();
// Clean-up
_sourceTextureParameter.SetValue((Texture2D)null);
_gBuffer0Parameter.SetValue((Texture2D)null);
_rayTextureParameter.SetValue((Texture2D)null);
renderTargetPool.Recycle(maskedScene);
renderTargetPool.Recycle(rayImage0);
renderTargetPool.Recycle(rayImage1);
context.SourceTexture = source;
context.RenderTarget = target;
context.Viewport = viewport;
}