fixing CSM gaps

Effects/DeferredPBREffect.cs

@@ -46,7 +46,7 @@ namespace Kav
         public Matrix LightSpaceMatrixFour { get; set; }
 
         public Matrix ViewMatrix { get; set; }
-        public float[] CascadeFarPlanes;
+        public readonly float[] CascadeFarPlanes;
 
         public Vector3 DirectionalLightColor { get; set; }
         public Vector3 DirectionalLightDirection { get; set; }

Effects/HLSL/DeferredPBREffect.fx

@@ -111,7 +111,7 @@ float ComputeShadow(float3 positionWorldSpace, float3 N, float L)
     int shadowCascadeIndex = 0; // 0 is closest
     for (int i = 0; i < NUM_SHADOW_CASCADES; i++)
     {
-        if (positionCameraSpace.z < CascadeFarPlanes[i])
+        if (abs(positionCameraSpace.z) < CascadeFarPlanes[i])
         {
             shadowCascadeIndex = i;
             break;
@@ -146,35 +146,61 @@ float ComputeShadow(float3 positionWorldSpace, float3 N, float L)
     projectionCoords.x = (projectionCoords.x * 0.5) + 0.5;
     projectionCoords.y = (projectionCoords.y * 0.5) + 0.5;
     projectionCoords.y *= -1;
+    // in XNA clip z is 0 to 1 already
 
+    float inc = 1.0 / 1024.0;
+
+    float shadowFactor = 0;
+    for (int row = -1; row <= 1; row++)
+    {
+        for (int col = -1; col <= 1; col++)
+        {
             float closestDepth;
             if (shadowCascadeIndex == 0)
             {
-        closestDepth = SAMPLE_TEXTURE(shadowMapOne, projectionCoords.xy).r;
+                closestDepth = SAMPLE_TEXTURE(shadowMapOne, projectionCoords.xy + float2(row, col) * inc).r;
             }
             else if (shadowCascadeIndex == 1)
             {
-        closestDepth = SAMPLE_TEXTURE(shadowMapTwo, projectionCoords.xy).r;
+                closestDepth = SAMPLE_TEXTURE(shadowMapTwo, projectionCoords.xy + float2(row, col) * inc).r;
             }
             else if (shadowCascadeIndex == 2)
             {
-        closestDepth = SAMPLE_TEXTURE(shadowMapThree, projectionCoords.xy).r;
+                closestDepth = SAMPLE_TEXTURE(shadowMapThree, projectionCoords.xy + float2(row, col) * inc).r;
             }
             else
             {
-        closestDepth = SAMPLE_TEXTURE(shadowMapFour, projectionCoords.xy).r;
+                closestDepth = SAMPLE_TEXTURE(shadowMapFour, projectionCoords.xy + float2(row, col) * inc).r;
+            }
+            shadowFactor += projectionCoords.z - bias > closestDepth ? 1.0 : 0.0;
+        }
     }
 
-    float currentDepth = projectionCoords.z;
+    shadowFactor /= 9.0;
 
-    if (currentDepth - bias > closestDepth)
+    if (projectionCoords.z > 1.0)
     {
-        return 1.0;
+        shadowFactor = 1.0;
-    }
-    else
-    {
-        return 0.0;
     }
+
+    return shadowFactor;
+
+
+    // float currentDepth = projectionCoords.z;
+
+    // if (currentDepth > 1.0)
+    // {
+    //     return 0.0;
+    // }
+
+    // if (currentDepth - bias > closestDepth)
+    // {
+    //     return 1.0;
+    // }
+    // else
+    // {
+    //     return 0.0;
+    // }
 }
 
 float3 ComputeLight(
@@ -239,7 +265,6 @@ float4 ComputeColor(
     float3 radiance = DirectionalLightColor;
 
     float shadow = ComputeShadow(worldPosition, N, L);
-
     Lo += ComputeLight(L, radiance, F0, V, N, albedo, metallic, roughness, (1.0 - shadow));
 
     float3 ambient = float3(0.03, 0.03, 0.03) * albedo; // * AO;

Effects/HLSL/SimpleDepthEffect.fx

@@ -24,7 +24,7 @@ VertexShaderOutput main_vs(VertexShaderInput input)
     VertexShaderOutput output;
 
     output.Position = mul(input.Position, ModelViewProjection);
-    output.Depth = output.Position.z / output.Position.w;
+    output.Depth = output.Position.z;
 
     return output;
 }

Renderer.cs

@@ -8,6 +8,7 @@ namespace Kav
     {
         private const int MAX_SHADOW_CASCADES = 4;
 
+
         private GraphicsDevice GraphicsDevice { get; }
         private int RenderDimensionsX { get; }
         private int RenderDimensionsY { get; }
@@ -235,11 +236,11 @@ namespace Kav
             
             // render the individual shadow maps
 
-            var frustumDistance = camera.FarPlane - camera.NearPlane;
+            var previousFarPlane = camera.NearPlane;
-            var sectionDistance = frustumDistance / NumShadowCascades;
-
             for (var i = 0; i < NumShadowCascades; i++)
             {
+                var farPlane = camera.FarPlane / (MathHelper.Max((NumShadowCascades - i - 1) * 5f, 1f));
+
                 // divide the view frustum 
                 var shadowCamera = new PerspectiveCamera(
                     camera.Position,
@@ -247,11 +248,13 @@ namespace Kav
                     camera.Up,
                     camera.FieldOfView,
                     camera.AspectRatio,
-                    camera.NearPlane + (i * sectionDistance),
+                    previousFarPlane,
-                    camera.NearPlane + ((i + 1) * sectionDistance)
+                    farPlane
                 );
                 
                 RenderShadowMap(shadowCamera, modelTransforms, directionalLight, i);
+
+                previousFarPlane = farPlane;
             }
         }
 
@@ -266,8 +269,6 @@ namespace Kav
             GraphicsDevice.DepthStencilState = DepthStencilState.Default;
             GraphicsDevice.BlendState = BlendState.Opaque;
             
-            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();
 
@@ -278,7 +279,7 @@ namespace Kav
             }
             frustumCenter /= 8f;
 
-            var lightView = Matrix.CreateLookAt(frustumCenter, frustumCenter - directionalLight.Direction, camera.View.Right);
+            var lightView = Matrix.CreateLookAt(frustumCenter + directionalLight.Direction, frustumCenter, Vector3.Backward);
 
             for (var i = 0; i < frustumCorners.Length; i++)
             {
@@ -286,16 +287,15 @@ namespace Kav
             }
 
             BoundingBox lightBox = BoundingBox.CreateFromPoints(frustumCorners);
-            Vector3 lightPosition = frustumCenter + directionalLight.Direction * -lightBox.Min.Z;
             
-            SimpleDepthEffect.View = Matrix.CreateLookAt(lightPosition, frustumCenter, camera.View.Right);
+            SimpleDepthEffect.View = lightView;
             SimpleDepthEffect.Projection = Matrix.CreateOrthographicOffCenter(
                 lightBox.Min.X,
                 lightBox.Max.X,
                 lightBox.Min.Y,
                 lightBox.Max.Y,
-                0,
+                -lightBox.Max.Z - 10f, // TODO: near clip plane needs scene AABB info to get rid of this magic value
-                lightBox.Max.Z - lightBox.Min.Z
+                -lightBox.Min.Z
             );
 
             var lightSpaceMatrix = SimpleDepthEffect.View * SimpleDepthEffect.Projection;