Graphics/ShadowMapping: Replace bias by a position scale

Inspired by Godot (see https://github.com/godotengine/godot-proposals/issues/4517)

src/Nazara/Graphics/Graphics.cpp

@@ -264,6 +264,8 @@ namespace Nz
 			settings.AddPass(depthPassIndex, depthPass);
 
 			MaterialPass shadowPass = depthPass;
+			shadowPass.options[CRC32("ShadowPass")] = true;
+			shadowPass.states.frontFace = FrontFace::Clockwise;
 			shadowPass.states.depthClamp = enabledFeatures.depthClamping;
 			settings.AddPass(shadowPassIndex, shadowPass);
 
@@ -290,6 +292,8 @@ namespace Nz
 			settings.AddPass(depthPassIndex, depthPass);
 
 			MaterialPass shadowPass = depthPass;
+			shadowPass.options[CRC32("ShadowPass")] = true;
+			shadowPass.states.frontFace = FrontFace::Clockwise;
 			shadowPass.states.depthClamp = enabledFeatures.depthClamping;
 			settings.AddPass(shadowPassIndex, shadowPass);
 
@@ -316,6 +320,8 @@ namespace Nz
 			settings.AddPass(depthPassIndex, depthPass);
 
 			MaterialPass shadowPass = depthPass;
+			shadowPass.options[CRC32("ShadowPass")] = true;
+			shadowPass.states.frontFace = FrontFace::Clockwise;
 			shadowPass.states.depthClamp = enabledFeatures.depthClamping;
 			settings.AddPass(shadowPassIndex, shadowPass);
 

src/Nazara/Graphics/PredefinedMaterials.cpp

@@ -16,6 +16,8 @@ namespace Nz
 		settings.AddValueProperty<Color>("BaseColor", Color::White());
 		settings.AddValueProperty<bool>("AlphaTest", false);
 		settings.AddValueProperty<float>("AlphaTestThreshold", 0.2f);
+		settings.AddValueProperty<float>("ShadowMapNormalOffset", 0.f);
+		settings.AddValueProperty<float>("ShadowPosScale", 1.f - 0.0025f);
 		settings.AddTextureProperty("BaseColorMap", ImageType::E2D);
 		settings.AddTextureProperty("AlphaMap", ImageType::E2D);
 		settings.AddPropertyHandler(std::make_unique<OptionValuePropertyHandler>("AlphaTest", "AlphaTest"));
@@ -23,6 +25,8 @@ namespace Nz
 		settings.AddPropertyHandler(std::make_unique<TexturePropertyHandler>("AlphaMap", "HasAlphaTexture"));
 		settings.AddPropertyHandler(std::make_unique<UniformValuePropertyHandler>("BaseColor"));
 		settings.AddPropertyHandler(std::make_unique<UniformValuePropertyHandler>("AlphaTestThreshold"));
+		settings.AddPropertyHandler(std::make_unique<UniformValuePropertyHandler>("ShadowMapNormalOffset"));
+		settings.AddPropertyHandler(std::make_unique<UniformValuePropertyHandler>("ShadowPosScale"));
 	}
 
 	void PredefinedMaterials::AddPbrSettings(MaterialSettings& settings)

src/Nazara/Graphics/Resources/Shaders/BasicMaterial.nzsl

@@ -9,6 +9,7 @@ import SkinLinearPosition from Engine.SkinningLinear;
 // Pass-specific options
 option DepthPass: bool = false;
 option DistanceDepth: bool = false;
+option ShadowPass: bool = false;
 
 // Material options
 option HasBaseColorTexture: bool = false;
@@ -23,12 +24,14 @@ option BillboardSizeRotLocation: i32 = -1;
 
 // Vertex declaration related options
 option VertexColorLoc: i32 = -1;
+option VertexNormalLoc: i32 = -1;
 option VertexPositionLoc: i32;
 option VertexUvLoc: i32 = -1;
 
 option VertexJointIndicesLoc: i32 = -1;
 option VertexJointWeightsLoc: i32 = -1;
 
+const HasNormal = (VertexNormalLoc >= 0);
 const HasVertexColor = (VertexColorLoc >= 0);
 const HasColor = (HasVertexColor || Billboard);
 const HasUV = (VertexUvLoc >= 0);
@@ -40,6 +43,12 @@ struct MaterialSettings
 	[tag("AlphaTestThreshold")]
 	AlphaThreshold: f32,
 
+	[tag("ShadowMapNormalOffset")]
+	ShadowMapNormalOffset: f32,
+
+	[tag("ShadowPosScale")]
+	ShadowPosScale: f32,
+
 	[tag("BaseColor")]
 	BaseColor: vec4[f32]
 }
@@ -157,6 +166,9 @@ struct VertIn
 	[cond(HasVertexColor), location(VertexColorLoc)] 
 	color: vec4[f32],
 
+	[cond(HasNormal), location(VertexNormalLoc)]
+	normal: vec3[f32],
+
 	[cond(HasUV), location(VertexUvLoc)] 
 	uv: vec2[f32],
 
@@ -230,6 +242,13 @@ fn main(input: VertIn) -> VertToFrag
 	else
 		pos = input.pos;
 
+	const if (ShadowPass)
+	{
+		pos *= settings.ShadowPosScale;
+		const if (HasNormal)
+			pos -= input.normal * settings.ShadowMapNormalOffset;
+	}
+
 	let worldPosition = instanceData.worldMatrix * vec4[f32](pos, 1.0);
 
 	let output: VertToFrag;

src/Nazara/Graphics/Resources/Shaders/Modules/Engine/LightShadow.nzsl

@@ -33,10 +33,6 @@ fn ComputeDirectionalLightShadow(light: DirectionalLight, shadowmap: depth_sampl
 			let lightProjPos = light.viewProjMatrices[cascadeIndex] * vec4[f32](worldPos, 1.0);
 			let shadowCoords = lightProjPos.xyz / lightProjPos.w;
 
-			// calculate bias (based on depth map resolution and slope)
-			let bias = max(0.05 * (1.0 - lambert), 0.005);
-			bias *= 1.0 / (light.cascadeDistances[cascadeIndex] * 0.05);
-
 			shadowFactor = 0.0;
 			[unroll]
 			for x in -1 -> 2
@@ -45,7 +41,7 @@ fn ComputeDirectionalLightShadow(light: DirectionalLight, shadowmap: depth_sampl
 				for y in -1 -> 2
 				{
 					let coords = shadowCoords.xy + vec2[f32](f32(x), f32(y)) * light.invShadowMapSize;
-					shadowFactor += shadowmap.SampleDepthComp(vec3[f32](coords, f32(cascadeIndex)), shadowCoords.z - bias).r;
+					shadowFactor += shadowmap.SampleDepthComp(vec3[f32](coords, f32(cascadeIndex)), shadowCoords.z).r;
 				}
 			}
 			shadowFactor /= 9.0;
@@ -74,8 +70,6 @@ fn ComputePointLightShadow(light: PointLight, shadowmap: sampler_cube[f32], dist
 			const start = vec3[f32](offset * 0.5, offset * 0.5, offset * 0.5);
 			const shadowContribution = 1.0 / f32(sampleCount * sampleCount * sampleCount);
 
-			let bias = 0.05;
-
 			[unroll]
 			for x in 0 -> sampleCount
 			{
@@ -91,7 +85,7 @@ fn ComputePointLightShadow(light: PointLight, shadowmap: sampler_cube[f32], dist
 						let closestDepth = shadowmap.Sample(sampleDir).r;
 						closestDepth *= light.radius;
 	
-						if (closestDepth > dist - bias)
+						if (closestDepth > dist)
 							shadowFactor += shadowContribution;
 					}
 				}
@@ -110,9 +104,6 @@ fn ComputeSpotLightShadow(light: SpotLight, shadowmap: depth_sampler2D[f32], wor
 	{
 		if (light.invShadowMapSize.x > 0.0)
 		{
-			let bias = 0.0005 * tan(acos(lambert));
-			bias = clamp(bias, 0.0, 0.01);
-
 			let lightProjPos = light.viewProjMatrix * vec4[f32](worldPos, 1.0);
 			let shadowCoords = lightProjPos.xyz / lightProjPos.w;
 
@@ -124,7 +115,7 @@ fn ComputeSpotLightShadow(light: SpotLight, shadowmap: depth_sampler2D[f32], wor
 				for y in -1 -> 2
 				{
 					let coords = shadowCoords.xy + vec2[f32](f32(x), f32(y)) * light.invShadowMapSize;
-					shadowFactor += shadowmap.SampleDepthComp(coords, shadowCoords.z - bias).r;
+					shadowFactor += shadowmap.SampleDepthComp(coords, shadowCoords.z).r;
 				}
 			}
 			shadowFactor /= 9.0;

src/Nazara/Graphics/Resources/Shaders/PhongMaterial.nzsl

@@ -12,6 +12,7 @@ import SkinLinearPosition, SkinLinearPositionNormal from Engine.SkinningLinear;
 // Pass-specific options
 option DepthPass: bool = false;
 option DistanceDepth: bool = false;
+option ShadowPass: bool = false;
 
 // Basic material options
 option HasBaseColorTexture: bool = false;
@@ -58,6 +59,12 @@ struct MaterialSettings
 	[tag("AlphaTestThreshold")]
 	AlphaThreshold: f32,
 
+	[tag("ShadowMapNormalOffset")]
+	ShadowMapNormalOffset: f32,
+
+	[tag("ShadowPosScale")]
+	ShadowPosScale: f32,
+
 	[tag("BaseColor")]
 	BaseColor: vec4[f32],
 
@@ -403,6 +410,13 @@ fn main(input: VertIn) -> VertToFrag
 			normal = input.normal;
 	}
 
+	const if (ShadowPass)
+	{
+		pos *= settings.ShadowPosScale;
+		const if (HasNormal)
+			pos -= input.normal * settings.ShadowMapNormalOffset;
+	}
+
 	let worldPosition = instanceData.worldMatrix * vec4[f32](pos, 1.0);
 
 	let output: VertToFrag;

src/Nazara/Graphics/Resources/Shaders/PhysicallyBasedMaterial.nzsl

@@ -12,6 +12,7 @@ import SkinLinearPosition, SkinLinearPositionNormal from Engine.SkinningLinear;
 // Pass-specific options
 option DepthPass: bool = false;
 option DistanceDepth: bool = false;
+option ShadowPass: bool = false;
 
 // Basic material options
 option HasBaseColorTexture: bool = false;
@@ -59,6 +60,12 @@ struct MaterialSettings
 	[tag("AlphaTestThreshold")]
 	AlphaThreshold: f32,
 
+	[tag("ShadowMapNormalOffset")]
+	ShadowMapNormalOffset: f32,
+
+	[tag("ShadowPosScale")]
+	ShadowPosScale: f32,
+
 	[tag("BaseColor")]
 	BaseColor: vec4[f32],
 }
@@ -387,6 +394,13 @@ fn main(input: VertIn) -> VertToFrag
 			normal = input.normal;
 	}
 
+	const if (ShadowPass)
+	{
+		pos *= settings.ShadowPosScale;
+		const if (HasNormal)
+			pos -= input.normal * settings.ShadowMapNormalOffset;
+	}
+
 	let worldPosition = instanceData.worldMatrix * vec4[f32](pos, 1.0);
 
 	let output: VertToFrag;