cascaded shadow maps

Cameras/Camera.cs

@@ -2,22 +2,32 @@ using Microsoft.Xna.Framework;
 
 namespace Kav
 {
-    public struct Camera
+    public struct PerspectiveCamera
     {
-        public Matrix Transform { get; }
+        public Matrix View { get; }
-        public Matrix View
-        {
-            get
-            {
-                return Matrix.CreateLookAt(Transform.Translation, Transform.Translation + Transform.Forward, Transform.Up);
-            }
-        }
         public Matrix Projection { get; }
 
-        public Camera(Matrix transform, Matrix projection)
+        public Vector3 Position { get; }
+        public Vector3 Forward { get; }
+        public Vector3 Up { get; }
+
+        public float FieldOfView { get; }
+        public float AspectRatio { get; }
+        public float NearPlane { get; }
+        public float FarPlane { get; }
+
+        public PerspectiveCamera(Vector3 position, Vector3 forward, Vector3 up, float fieldOfView, float aspectRatio, float nearPlane, float farPlane)
         {
-            Transform = transform;
+            Position = position;
-            Projection = projection;
+            Forward = forward;
+            Up = up;
+            View = Matrix.CreateLookAt(Position, Position + Forward, Up);
+
+            FieldOfView = fieldOfView;
+            AspectRatio = aspectRatio;
+            NearPlane = nearPlane;
+            FarPlane = farPlane;    
+            Projection = Matrix.CreatePerspectiveFieldOfView(FieldOfView, AspectRatio, NearPlane, FarPlane);
         }
     }
 }

Effects/DeferredPBREffect.cs

@@ -9,13 +9,24 @@ namespace Kav
         EffectParameter gAlbedoParam;
         EffectParameter gNormalParam;
         EffectParameter gMetallicRoughnessParam;
-        EffectParameter shadowMapParam;
+
+        EffectParameter shadowMapOneParam;
+        EffectParameter shadowMapTwoParam;
+        EffectParameter shadowMapThreeParam;
+        EffectParameter shadowMapFourParam;
+
+        EffectParameter lightSpaceMatrixOneParam;
+        EffectParameter lightSpaceMatrixTwoParam;
+        EffectParameter lightSpaceMatrixThreeParam;
+        EffectParameter lightSpaceMatrixFourParam;
+
+        EffectParameter viewMatrixParam;
+        EffectParameter cascadeFarPlanesParam;
 
         EffectParameter directionalLightColorParam;
         EffectParameter directionalLightDirectionParam;
 
         EffectParameter eyePositionParam;
-        EffectParameter lightSpaceMatrixParam;
 
         PointLightCollection pointLightCollection;
 
@@ -23,11 +34,22 @@ namespace Kav
         public Texture2D GAlbedo { get; set; }
         public Texture2D GNormal { get; set; }
         public Texture2D GMetallicRoughness { get; set; }
-        public Texture2D ShadowMap { get; set; }
+
+        public Texture2D ShadowMapOne { get; set; }
+        public Texture2D ShadowMapTwo { get; set; }
+        public Texture2D ShadowMapThree { get; set; }
+        public Texture2D ShadowMapFour { get; set; }
+
+        public Matrix LightSpaceMatrixOne { get; set; }
+        public Matrix LightSpaceMatrixTwo { get; set; }
+        public Matrix LightSpaceMatrixThree { get; set; }
+        public Matrix LightSpaceMatrixFour { get; set; }
+
+        public Matrix ViewMatrix { get; set; }
+        public float[] CascadeFarPlanes;
 
         public Vector3 DirectionalLightColor { get; set; }
         public Vector3 DirectionalLightDirection { get; set; }
-        public Matrix LightSpaceMatrix { get; set; }
 
         public Vector3 EyePosition { get; set; }
 
@@ -41,6 +63,8 @@ namespace Kav
 
         public DeferredPBREffect(GraphicsDevice graphicsDevice) : base(graphicsDevice, Resources.DeferredPBREffect)
         {
+            CascadeFarPlanes = new float[4];
+
             CacheEffectParameters();
 
             pointLightCollection = new PointLightCollection(
@@ -82,28 +106,50 @@ namespace Kav
             gAlbedoParam.SetValue(GAlbedo);
             gNormalParam.SetValue(GNormal);
             gMetallicRoughnessParam.SetValue(GMetallicRoughness);
-            shadowMapParam.SetValue(ShadowMap);
+
+            shadowMapOneParam.SetValue(ShadowMapOne);
+            shadowMapTwoParam.SetValue(ShadowMapTwo);
+            shadowMapThreeParam.SetValue(ShadowMapThree);
+            shadowMapFourParam.SetValue(ShadowMapFour);
+
+            lightSpaceMatrixOneParam.SetValue(LightSpaceMatrixOne);
+            lightSpaceMatrixTwoParam.SetValue(LightSpaceMatrixTwo);
+            lightSpaceMatrixThreeParam.SetValue(LightSpaceMatrixThree);
+            lightSpaceMatrixFourParam.SetValue(LightSpaceMatrixFour);
+
+            viewMatrixParam.SetValue(ViewMatrix);
+            cascadeFarPlanesParam.SetValue(CascadeFarPlanes);
 
             directionalLightColorParam.SetValue(DirectionalLightColor);
             directionalLightDirectionParam.SetValue(DirectionalLightDirection);
 
             eyePositionParam.SetValue(EyePosition);
-            lightSpaceMatrixParam.SetValue(LightSpaceMatrix);
         }
 
         void CacheEffectParameters()
         {
-            gPositionParam = Parameters["gPosition"];
+            gPositionParam                 = Parameters["gPosition"];
-            gAlbedoParam = Parameters["gAlbedo"];
+            gAlbedoParam                   = Parameters["gAlbedo"];
-            gNormalParam = Parameters["gNormal"];
+            gNormalParam                   = Parameters["gNormal"];
-            gMetallicRoughnessParam = Parameters["gMetallicRoughness"];
+            gMetallicRoughnessParam        = Parameters["gMetallicRoughness"];
-            shadowMapParam = Parameters["shadowMap"];
+
+            shadowMapOneParam              = Parameters["shadowMapOne"];
+            shadowMapTwoParam              = Parameters["shadowMapTwo"];
+            shadowMapThreeParam            = Parameters["shadowMapThree"];
+            shadowMapFourParam             = Parameters["shadowMapFour"];
+
+            lightSpaceMatrixOneParam       = Parameters["LightSpaceMatrixOne"];
+            lightSpaceMatrixTwoParam       = Parameters["LightSpaceMatrixTwo"];
+            lightSpaceMatrixThreeParam     = Parameters["LightSpaceMatrixThree"];
+            lightSpaceMatrixFourParam      = Parameters["LightSpaceMatrixFour"];
+
+            viewMatrixParam                = Parameters["ViewMatrix"];
+            cascadeFarPlanesParam          = Parameters["CascadeFarPlanes"];
 
             directionalLightDirectionParam = Parameters["DirectionalLightDirection"];
-            directionalLightColorParam = Parameters["DirectionalLightColor"];
+            directionalLightColorParam     = Parameters["DirectionalLightColor"];
-            lightSpaceMatrixParam = Parameters["LightSpaceMatrix"];
 
-            eyePositionParam = Parameters["EyePosition"];
+            eyePositionParam               = Parameters["EyePosition"];
         }
     }
 }

Effects/HLSL/DeferredPBREffect.fx

@@ -2,12 +2,16 @@
 
 static const float PI = 3.141592653589793;
 static const int MAX_POINT_LIGHTS = 64;
+static const int NUM_SHADOW_CASCADES = 4;
 
 DECLARE_TEXTURE(gPosition, 0);
 DECLARE_TEXTURE(gAlbedo, 1);
 DECLARE_TEXTURE(gNormal, 2);
 DECLARE_TEXTURE(gMetallicRoughness, 3);
-DECLARE_TEXTURE(shadowMap, 4);
+DECLARE_TEXTURE(shadowMapOne, 4);
+DECLARE_TEXTURE(shadowMapTwo, 5);
+DECLARE_TEXTURE(shadowMapThree, 6);
+DECLARE_TEXTURE(shadowMapFour, 7);
 
 BEGIN_CONSTANTS
 
@@ -19,9 +23,17 @@ BEGIN_CONSTANTS
     float3 DirectionalLightDirection                           _ps(c129)   _cb(c129);
     float3 DirectionalLightColor                               _ps(c130)   _cb(c130);
 
+    float CascadeFarPlanes[NUM_SHADOW_CASCADES]                _ps(c131)   _cb(c131);
+
 MATRIX_CONSTANTS
 
-    float4x4 LightSpaceMatrix                                  _ps(c131)   _cb(c131);
+    float4x4 LightSpaceMatrixOne                               _ps(c135)   _cb(c135);
+    float4x4 LightSpaceMatrixTwo                               _ps(c139)   _cb(c139);
+    float4x4 LightSpaceMatrixThree                             _ps(c143)   _cb(c143);
+    float4x4 LightSpaceMatrixFour                              _ps(c147)   _cb(c147);
+
+    // used to select shadow cascade
+    float4x4 ViewMatrix                                        _ps(c151)   _cb(c151);
 
 END_CONSTANTS
 
@@ -89,11 +101,44 @@ float GeometrySmith(float3 N, float3 V, float3 L, float roughness)
     return ggx1 * ggx2;
 }
 
-float ComputeShadow(float4 positionLightSpace, float3 N, float L)
+float ComputeShadow(float3 positionWorldSpace, float3 N, float L)
 {
     float bias = 0.005 * tan(acos(dot(N, L)));
     bias = clamp(bias, 0, 0.01);
 
+    float4 positionCameraSpace = mul(float4(positionWorldSpace, 1.0), ViewMatrix);
+
+    int shadowCascadeIndex = 0; // 0 is closest
+    for (int i = 0; i < NUM_SHADOW_CASCADES; i++)
+    {
+        if (positionCameraSpace.z < CascadeFarPlanes[i])
+        {
+            shadowCascadeIndex = i;
+            break;
+        }
+    }
+
+    float4x4 lightSpaceMatrix;
+
+    if (shadowCascadeIndex == 0)
+    {
+        lightSpaceMatrix = LightSpaceMatrixOne;
+    }
+    else if (shadowCascadeIndex == 1)
+    {
+        lightSpaceMatrix = LightSpaceMatrixTwo;
+    }
+    else if (shadowCascadeIndex == 2)
+    {
+        lightSpaceMatrix = LightSpaceMatrixThree;
+    }
+    else
+    {
+        lightSpaceMatrix = LightSpaceMatrixFour;
+    }
+
+    float4 positionLightSpace = mul(float4(positionWorldSpace, 1.0), lightSpaceMatrix);
+   
     // maps to [-1, 1]
     float3 projectionCoords = positionLightSpace.xyz / positionLightSpace.w;
 
@@ -102,7 +147,24 @@ float ComputeShadow(float4 positionLightSpace, float3 N, float L)
     projectionCoords.y = (projectionCoords.y * 0.5) + 0.5;
     projectionCoords.y *= -1;
 
-    float closestDepth = SAMPLE_TEXTURE(shadowMap, projectionCoords.xy).r;
+    float closestDepth;
+    if (shadowCascadeIndex == 0)
+    {
+        closestDepth = SAMPLE_TEXTURE(shadowMapOne, projectionCoords.xy).r;
+    }
+    else if (shadowCascadeIndex == 1)
+    {
+        closestDepth = SAMPLE_TEXTURE(shadowMapTwo, projectionCoords.xy).r;
+    }
+    else if (shadowCascadeIndex == 2)
+    {
+        closestDepth = SAMPLE_TEXTURE(shadowMapThree, projectionCoords.xy).r;
+    }
+    else
+    {
+        closestDepth = SAMPLE_TEXTURE(shadowMapFour, projectionCoords.xy).r;
+    }
+
     float currentDepth = projectionCoords.z;
 
     if (currentDepth - bias > closestDepth)
@@ -176,8 +238,7 @@ float4 ComputeColor(
     float3 L = normalize(DirectionalLightDirection);
     float3 radiance = DirectionalLightColor;
 
-    float4 positionLightSpace = mul(float4(worldPosition, 1.0), LightSpaceMatrix);
+    float shadow = ComputeShadow(worldPosition, N, L);
-    float shadow = ComputeShadow(positionLightSpace, N, L);
 
     Lo += ComputeLight(L, radiance, F0, V, N, albedo, metallic, roughness, (1.0 - shadow));
 

Renderer.cs

@@ -6,12 +6,15 @@ namespace Kav
 {
     public class Renderer
     {
+        private const int MAX_SHADOW_CASCADES = 4;
+
         private GraphicsDevice GraphicsDevice { get; }
         private int RenderDimensionsX { get; }
         private int RenderDimensionsY { get; }
 
         private VertexBuffer FullscreenTriangle { get; }
-        private RenderTarget2D ShadowRenderTarget { get; }
+        private int NumShadowCascades { get; }
+        private RenderTarget2D[] ShadowRenderTargets { get; }
 
         private DeferredPBREffect DeferredPBREffect { get; }
         private SimpleDepthEffect SimpleDepthEffect { get; }
@@ -24,22 +27,26 @@ namespace Kav
 
         private RenderTargetBinding[] GBuffer { get; }
 
-        private SpriteBatch SpriteBatch { get; }
+        public Renderer(GraphicsDevice graphicsDevice, int renderDimensionsX, int renderDimensionsY, int numShadowCascades)
-
-        public Renderer(GraphicsDevice graphicsDevice, int renderDimensionsX, int renderDimensionsY)
         {
             GraphicsDevice = graphicsDevice;
             RenderDimensionsX = renderDimensionsX;
             RenderDimensionsY = renderDimensionsY;
 
-            ShadowRenderTarget = new RenderTarget2D(
+            NumShadowCascades = (int)MathHelper.Clamp(numShadowCascades, 1, MAX_SHADOW_CASCADES);
-                GraphicsDevice,
+            ShadowRenderTargets = new RenderTarget2D[numShadowCascades];
-                1024,
+
-                1024,
+            for (var i = 0; i < numShadowCascades; i++)
-                false,
+            {
-                SurfaceFormat.Single,
+                ShadowRenderTargets[i] = new RenderTarget2D(
-                DepthFormat.Depth24
+                    GraphicsDevice,
-            );
+                    1024,
+                    1024,
+                    false,
+                    SurfaceFormat.Single,
+                    DepthFormat.Depth24
+                );
+            }
 
             gPosition = new RenderTarget2D(
                 GraphicsDevice,
@@ -100,21 +107,18 @@ namespace Kav
                 new VertexPositionTexture(new Vector3(3, -1, 0), new Vector2(2, 0))
             });
 
-            SpriteBatch = new SpriteBatch(GraphicsDevice);
-
             GraphicsDevice.SetRenderTarget(deferredRenderTarget);
             graphicsDevice.Clear(Color.White);
             GraphicsDevice.SetRenderTarget(null);
         }
 
         public void DeferredRender(
-            Camera camera,
+            PerspectiveCamera camera,
             IEnumerable<(Model, Matrix)> modelTransforms,
             IEnumerable<PointLight> pointLights,
-            DirectionalLight directionalLight,
+            DirectionalLight directionalLight
-            int numCascades
         ) {
-            ShadowMapRender(camera, modelTransforms, directionalLight, numCascades);
+            ShadowMapRender(camera, modelTransforms, directionalLight);
 
             GraphicsDevice.SetRenderTargets(GBuffer);
             GraphicsDevice.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1f, 0);
@@ -161,7 +165,23 @@ namespace Kav
             DeferredPBREffect.GAlbedo = gAlbedo;
             DeferredPBREffect.GNormal = gNormal;
             DeferredPBREffect.GMetallicRoughness = gMetallicRoughness;
-            DeferredPBREffect.ShadowMap = ShadowRenderTarget;
+            
+            DeferredPBREffect.ShadowMapOne = ShadowRenderTargets[0];
+            if (NumShadowCascades > 1)
+            {
+                DeferredPBREffect.ShadowMapTwo = ShadowRenderTargets[1];
+            }
+            if (NumShadowCascades > 2)
+            {
+                DeferredPBREffect.ShadowMapThree = ShadowRenderTargets[2];
+            }
+            if (NumShadowCascades > 3)
+            {
+                DeferredPBREffect.ShadowMapFour = ShadowRenderTargets[3];
+            }
+
+            DeferredPBREffect.ViewMatrix = camera.View;
+
             DeferredPBREffect.EyePosition = Matrix.Invert(camera.View).Translation;
 
             int i = 0;
@@ -182,19 +202,66 @@ namespace Kav
                 GraphicsDevice.SetVertexBuffer(FullscreenTriangle);
                 GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, 1);
             }
-
-            // SpriteBatch.Begin(SpriteSortMode.Deferred, BlendState.NonPremultiplied, null, null, null, DeferredPBREffect);
-            // SpriteBatch.Draw(deferredRenderTarget, Vector2.Zero, Color.White);
-            // SpriteBatch.End();
         }
 
         public void ShadowMapRender(
-            Camera camera, 
+            PerspectiveCamera camera, 
+            IEnumerable<(Model, Matrix)> modelTransforms, 
+            DirectionalLight directionalLight
+        ) {
+            // set up global light matrix
+
+            var right = Vector3.Cross(Vector3.Up, directionalLight.Direction);
+            var up = Vector3.Cross(directionalLight.Direction, right);
+            var cameraBoundingFrustum = new BoundingFrustum(camera.View * camera.Projection);
+            Vector3[] frustumCorners = cameraBoundingFrustum.GetCorners();
+
+            Vector3 frustumCenter = Vector3.Zero;
+            for (var i = 0; i < frustumCorners.Length; i++)
+            {
+                frustumCenter += frustumCorners[i];
+            }
+            frustumCenter /= 8f;
+
+            var lightView = Matrix.CreateLookAt(frustumCenter, frustumCenter - directionalLight.Direction, camera.View.Right);
+
+            for (var i = 0; i < frustumCorners.Length; i++)
+            {
+                frustumCorners[i] = Vector3.Transform(frustumCorners[i], lightView);
+            }
+
+            BoundingBox lightBox = BoundingBox.CreateFromPoints(frustumCorners);
+            Vector3 lightPosition = frustumCenter + directionalLight.Direction * -lightBox.Min.Z;
+            
+            // render the individual shadow maps
+
+            var frustumDistance = camera.FarPlane - camera.NearPlane;
+            var sectionDistance = frustumDistance / NumShadowCascades;
+
+            for (var i = 0; i < NumShadowCascades; i++)
+            {
+                // divide the view frustum 
+                var shadowCamera = new PerspectiveCamera(
+                    camera.Position,
+                    camera.Forward,
+                    camera.Up,
+                    camera.FieldOfView,
+                    camera.AspectRatio,
+                    camera.NearPlane + (i * sectionDistance),
+                    camera.NearPlane + ((i + 1) * sectionDistance)
+                );
+                
+                RenderShadowMap(shadowCamera, modelTransforms, directionalLight, i);
+            }
+        }
+
+        private void RenderShadowMap(
+            PerspectiveCamera camera, 
             IEnumerable<(Model, Matrix)> modelTransforms, 
             DirectionalLight directionalLight,
-            int numCascades
+            int shadowCascadeIndex
         ) {
-            GraphicsDevice.SetRenderTarget(ShadowRenderTarget);
+            GraphicsDevice.SetRenderTarget(ShadowRenderTargets[shadowCascadeIndex]);
             GraphicsDevice.Clear(Color.White);
             GraphicsDevice.DepthStencilState = DepthStencilState.Default;
             GraphicsDevice.BlendState = BlendState.Opaque;
@@ -230,70 +297,27 @@ namespace Kav
                 0,
                 lightBox.Max.Z - lightBox.Min.Z
             );
-            DeferredPBREffect.LightSpaceMatrix = SimpleDepthEffect.View * SimpleDepthEffect.Projection;
 
-            foreach (var (model, transform) in modelTransforms)
+            var lightSpaceMatrix = SimpleDepthEffect.View * SimpleDepthEffect.Projection;
+
+            if (shadowCascadeIndex == 0)
             {
-                foreach (var modelMesh in model.Meshes)
+                DeferredPBREffect.LightSpaceMatrixOne = lightSpaceMatrix;
-                {
-                    foreach (var meshPart in modelMesh.MeshParts)
-                    {
-                        GraphicsDevice.SetVertexBuffer(meshPart.VertexBuffer);
-                        GraphicsDevice.Indices = meshPart.IndexBuffer;
-
-                        SimpleDepthEffect.Model = transform;
-
-                        foreach (var pass in SimpleDepthEffect.CurrentTechnique.Passes)
-                        {
-                            pass.Apply();
-
-                            GraphicsDevice.DrawIndexedPrimitives(
-                                PrimitiveType.TriangleList,
-                                0,
-                                0,
-                                meshPart.VertexBuffer.VertexCount,
-                                0,
-                                meshPart.Triangles.Length
-                            );
-                        }
-                    }
-                }
             }
-        }
+            else if (shadowCascadeIndex == 1)
-
-        private void RenderShadowMap(Camera camera, IEnumerable<(Model, Matrix)> modelTransforms, DirectionalLight directionalLight)
-        {
-            var right = Vector3.Cross(Vector3.Up, directionalLight.Direction);
-            var up = Vector3.Cross(directionalLight.Direction, right);
-            var cameraBoundingFrustum = new BoundingFrustum(camera.View * camera.Projection);
-            Vector3[] frustumCorners = cameraBoundingFrustum.GetCorners();
-
-            Vector3 frustumCenter = Vector3.Zero;
-            for (var i = 0; i < frustumCorners.Length; i++)
             {
-                frustumCenter += frustumCorners[i];
+                DeferredPBREffect.LightSpaceMatrixTwo = lightSpaceMatrix;
             }
-            frustumCenter /= 8f;
+            else if (shadowCascadeIndex == 2)
-
-            var lightView = Matrix.CreateLookAt(frustumCenter, frustumCenter - directionalLight.Direction, camera.View.Right);
-
-            for (var i = 0; i < frustumCorners.Length; i++)
             {
-                frustumCorners[i] = Vector3.Transform(frustumCorners[i], lightView);
+                DeferredPBREffect.LightSpaceMatrixThree = lightSpaceMatrix;
+            }
+            else if (shadowCascadeIndex == 3)
+            {
+                DeferredPBREffect.LightSpaceMatrixFour = lightSpaceMatrix;
             }
 
-            BoundingBox lightBox = BoundingBox.CreateFromPoints(frustumCorners);
+            DeferredPBREffect.CascadeFarPlanes[shadowCascadeIndex] = camera.FarPlane;
-            Vector3 lightPosition = frustumCenter + directionalLight.Direction * -lightBox.Min.Z;
-            
-            SimpleDepthEffect.View = Matrix.CreateLookAt(lightPosition, frustumCenter, camera.View.Right);
-            SimpleDepthEffect.Projection = Matrix.CreateOrthographicOffCenter(
-                lightBox.Min.X,
-                lightBox.Max.X,
-                lightBox.Min.Y,
-                lightBox.Max.Y,
-                0,
-                lightBox.Max.Z - lightBox.Min.Z
-            );
 
             foreach (var (model, transform) in modelTransforms)
             {
@@ -325,7 +349,7 @@ namespace Kav
         }
 
         public void Render(
-            Camera camera, 
+            PerspectiveCamera camera, 
             IEnumerable<(Model, Matrix)> modelTransforms, 
             IEnumerable<PointLight> pointLights,
             IEnumerable<DirectionalLight> directionalLights