Implement shadow offsets for the new SM distortion function (#12191)

* Move shadow position calculation to vertex shaders
* Animate entire scene before rendering shadows to prevent lagging of shadows
* Remove unnecessary use of PolygonOffsetFactor
* Apply normal offset to both nodes and objects
* Rename getPerspectiveFactor -> applyPerspectiveDistortion
* Remove perspective distortion from fragment shaders

client/shaders/nodes_shader/opengl_fragment.glsl

@@ -18,10 +18,13 @@ uniform float animationTimer;
 	uniform float f_shadowfar;
 	uniform float f_shadow_strength;
 	uniform vec4 CameraPos;
-	varying float normalOffsetScale;
+	uniform float xyPerspectiveBias0;
+	uniform float xyPerspectiveBias1;
+	
 	varying float adj_shadow_strength;
 	varying float cosLight;
 	varying float f_normal_length;
+	varying vec3 shadow_position;
 #endif
 
 
@@ -45,24 +48,7 @@ varying float nightRatio;
 const float fogStart = FOG_START;
 const float fogShadingParameter = 1.0 / ( 1.0 - fogStart);
 
-
-
 #ifdef ENABLE_DYNAMIC_SHADOWS
-uniform float xyPerspectiveBias0;
-uniform float xyPerspectiveBias1;
-uniform float zPerspectiveBias;
-
-vec4 getPerspectiveFactor(in vec4 shadowPosition)
-{
-	vec2 s = vec2(shadowPosition.x > CameraPos.x ? 1.0 : -1.0, shadowPosition.y > CameraPos.y ? 1.0 : -1.0);
-	vec2 l = s * (shadowPosition.xy - CameraPos.xy) / (1.0 - s * CameraPos.xy);
-	float pDistance = length(l);
-	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
-	l /= pFactor;
-	shadowPosition.xy = CameraPos.xy * (1.0 - l) + s * l;
-	shadowPosition.z *= zPerspectiveBias;
-	return shadowPosition;
-}
 
 // assuming near is always 1.0
 float getLinearDepth()
@@ -72,15 +58,7 @@ float getLinearDepth()
 
 vec3 getLightSpacePosition()
 {
-	vec4 pLightSpace;
-	// some drawtypes have zero normals, so we need to handle it :(
-	#if DRAW_TYPE == NDT_PLANTLIKE
-	pLightSpace = m_ShadowViewProj * vec4(worldPosition, 1.0);
-	#else
-	pLightSpace = m_ShadowViewProj * vec4(worldPosition + normalOffsetScale * normalize(vNormal), 1.0);
-	#endif
-	pLightSpace = getPerspectiveFactor(pLightSpace);
-	return pLightSpace.xyz * 0.5 + 0.5;
+	return shadow_position * 0.5 + 0.5;
 }
 // custom smoothstep implementation because it's not defined in glsl1.2
 // https://docs.gl/sl4/smoothstep
@@ -499,14 +477,14 @@ void main(void)
 
 #ifdef COLORED_SHADOWS
 			vec4 visibility;
-			if (cosLight > 0.0)
+			if (cosLight > 0.0 || f_normal_length < 1e-3)
 				visibility = getShadowColor(ShadowMapSampler, posLightSpace.xy, posLightSpace.z);
 			else
 				visibility = vec4(1.0, 0.0, 0.0, 0.0);
 			shadow_int = visibility.r;
 			shadow_color = visibility.gba;
 #else
-			if (cosLight > 0.0)
+			if (cosLight > 0.0 || f_normal_length < 1e-3)
 				shadow_int = getShadow(ShadowMapSampler, posLightSpace.xy, posLightSpace.z);
 			else
 				shadow_int = 1.0;

client/shaders/nodes_shader/opengl_vertex.glsl

@@ -32,10 +32,13 @@ centroid varying vec2 varTexCoord;
 	uniform float f_shadowfar;
 	uniform float f_shadow_strength;
 	uniform float f_timeofday;
+	uniform vec4 CameraPos;
+
 	varying float cosLight;
 	varying float normalOffsetScale;
 	varying float adj_shadow_strength;
 	varying float f_normal_length;
+	varying vec3 shadow_position;
 #endif
 
 
@@ -47,8 +50,36 @@ const float e = 2.718281828459;
 const float BS = 10.0;
 uniform float xyPerspectiveBias0;
 uniform float xyPerspectiveBias1;
+uniform float zPerspectiveBias;
 
 #ifdef ENABLE_DYNAMIC_SHADOWS
+
+vec4 getRelativePosition(in vec4 position)
+{
+	vec2 l = position.xy - CameraPos.xy;
+	vec2 s = l / abs(l);
+	s = (1.0 - s * CameraPos.xy);
+	l /= s;
+	return vec4(l, s);
+}
+
+float getPerspectiveFactor(in vec4 relativePosition)
+{
+	float pDistance = length(relativePosition.xy);
+	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
+	return pFactor;
+}
+
+vec4 applyPerspectiveDistortion(in vec4 position)
+{
+	vec4 l = getRelativePosition(position);
+	float pFactor = getPerspectiveFactor(l);
+	l.xy /= pFactor;
+	position.xy = l.xy * l.zw + CameraPos.xy;
+	position.z *= zPerspectiveBias;
+	return position;
+}
+
 // custom smoothstep implementation because it's not defined in glsl1.2
 // https://docs.gl/sl4/smoothstep
 float mtsmoothstep(in float edge0, in float edge1, in float x)
@@ -196,21 +227,32 @@ void main(void)
 
 #ifdef ENABLE_DYNAMIC_SHADOWS
 	if (f_shadow_strength > 0.0) {
-		vec3 nNormal = normalize(vNormal);
-		cosLight = dot(nNormal, -v_LightDirection);
-		
-		// Calculate normal offset scale based on the texel size adjusted for
-		// curvature of the SM texture. This code must be change together with
-		// getPerspectiveFactor or any light-space transformation.
-		vec3 eyeToVertex = worldPosition - eyePosition + cameraOffset;
-		// Distance from the vertex to the player
-		float distanceToPlayer = length(eyeToVertex - v_LightDirection * dot(eyeToVertex, v_LightDirection)) / f_shadowfar;
-		// perspective factor estimation according to the
-		float perspectiveFactor = distanceToPlayer * xyPerspectiveBias0 + xyPerspectiveBias1;
-		float texelSize = f_shadowfar * perspectiveFactor * perspectiveFactor /
-				(f_textureresolution * xyPerspectiveBias1  - perspectiveFactor * xyPerspectiveBias0);
-		float slopeScale = clamp(pow(1.0 - cosLight*cosLight, 0.5), 0.0, 1.0);
-		normalOffsetScale = texelSize * slopeScale;
+		vec3 nNormal;
+		f_normal_length = length(vNormal);
+
+		/* normalOffsetScale is in world coordinates (1/10th of a meter)
+		   z_bias is in light space coordinates */
+		float normalOffsetScale, z_bias;
+		float pFactor = getPerspectiveFactor(getRelativePosition(m_ShadowViewProj * mWorld * inVertexPosition));
+		if (f_normal_length > 0.0) {
+			nNormal = normalize(vNormal);
+			cosLight = dot(nNormal, -v_LightDirection);
+			float sinLight = pow(1 - pow(cosLight, 2.0), 0.5);
+			normalOffsetScale = 2.0 * pFactor * pFactor * sinLight * min(f_shadowfar, 500.0) / 
+					xyPerspectiveBias1 / f_textureresolution;
+			z_bias = 1.0 * sinLight / cosLight;
+		}
+		else {
+			nNormal = vec3(0.0);
+			cosLight = clamp(dot(v_LightDirection, normalize(vec3(v_LightDirection.x, 0.0, v_LightDirection.z))), 1e-2, 1.0);
+			float sinLight = pow(1 - pow(cosLight, 2.0), 0.5);
+			normalOffsetScale = 0.0;
+			z_bias = 3.6e3 * sinLight / cosLight;
+		}
+		z_bias *= pFactor * pFactor / f_textureresolution / f_shadowfar;
+
+		shadow_position = applyPerspectiveDistortion(m_ShadowViewProj * mWorld * (inVertexPosition + vec4(normalOffsetScale * nNormal, 0.0))).xyz;
+		shadow_position.z -= z_bias;
 
 		if (f_timeofday < 0.2) {
 			adj_shadow_strength = f_shadow_strength * 0.5 *
@@ -223,7 +265,6 @@ void main(void)
 				mtsmoothstep(0.20, 0.25, f_timeofday) *
 				(1.0 - mtsmoothstep(0.7, 0.8, f_timeofday));
 		}
-		f_normal_length = length(vNormal);
 	}
 #endif
 }

client/shaders/object_shader/opengl_fragment.glsl

@@ -19,10 +19,13 @@ uniform float animationTimer;
 	uniform float f_shadowfar;
 	uniform float f_shadow_strength;
 	uniform vec4 CameraPos;
-	varying float normalOffsetScale;
+	uniform float xyPerspectiveBias0;
+	uniform float xyPerspectiveBias1;
+	
 	varying float adj_shadow_strength;
 	varying float cosLight;
 	varying float f_normal_length;
+	varying vec3 shadow_position;
 #endif
 
 
@@ -48,24 +51,7 @@ varying float vIDiff;
 const float fogStart = FOG_START;
 const float fogShadingParameter = 1.0 / (1.0 - fogStart);
 
-
-
 #ifdef ENABLE_DYNAMIC_SHADOWS
-uniform float xyPerspectiveBias0;
-uniform float xyPerspectiveBias1;
-uniform float zPerspectiveBias;
-
-vec4 getPerspectiveFactor(in vec4 shadowPosition)
-{
-	vec2 s = vec2(shadowPosition.x > CameraPos.x ? 1.0 : -1.0, shadowPosition.y > CameraPos.y ? 1.0 : -1.0);
-	vec2 l = s * (shadowPosition.xy - CameraPos.xy) / (1.0 - s * CameraPos.xy);
-	float pDistance = length(l);
-	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
-	l /= pFactor;
-	shadowPosition.xy = CameraPos.xy * (1.0 - l) + s * l;
-	shadowPosition.z *= zPerspectiveBias;
-	return shadowPosition;
-}
 
 // assuming near is always 1.0
 float getLinearDepth()
@@ -75,15 +61,7 @@ float getLinearDepth()
 
 vec3 getLightSpacePosition()
 {
-	vec4 pLightSpace;
-	// some drawtypes have zero normals, so we need to handle it :(
-	#if DRAW_TYPE == NDT_PLANTLIKE
-	pLightSpace = m_ShadowViewProj * vec4(worldPosition, 1.0);
-	#else
-	pLightSpace = m_ShadowViewProj * vec4(worldPosition + normalOffsetScale * normalize(vNormal), 1.0);
-	#endif
-	pLightSpace = getPerspectiveFactor(pLightSpace);
-	return pLightSpace.xyz * 0.5 + 0.5;
+	return shadow_position * 0.5 + 0.5;
 }
 // custom smoothstep implementation because it's not defined in glsl1.2
 // https://docs.gl/sl4/smoothstep
@@ -503,13 +481,14 @@ void main(void)
 
 #ifdef COLORED_SHADOWS
 			vec4 visibility;
-			if (cosLight > 0.0)
+			if (cosLight > 0.0 || f_normal_length < 1e-3)
 				visibility = getShadowColor(ShadowMapSampler, posLightSpace.xy, posLightSpace.z);
 			else
 				visibility = vec4(1.0, 0.0, 0.0, 0.0);
 			shadow_int = visibility.r;
 			shadow_color = visibility.gba;
 #else
+			if (cosLight > 0.0 || f_normal_length < 1e-3)
 			if (cosLight > 0.0)
 				shadow_int = getShadow(ShadowMapSampler, posLightSpace.xy, posLightSpace.z);
 			else

client/shaders/object_shader/opengl_vertex.glsl

@@ -24,10 +24,12 @@ centroid varying vec2 varTexCoord;
 	uniform float f_shadowfar;
 	uniform float f_shadow_strength;
 	uniform float f_timeofday;
+	uniform vec4 CameraPos;
+
 	varying float cosLight;
-	varying float normalOffsetScale;
 	varying float adj_shadow_strength;
 	varying float f_normal_length;
+	varying vec3 shadow_position;
 #endif
 
 varying vec3 eyeVec;
@@ -39,8 +41,36 @@ const float e = 2.718281828459;
 const float BS = 10.0;
 uniform float xyPerspectiveBias0;
 uniform float xyPerspectiveBias1;
+uniform float zPerspectiveBias;
 
 #ifdef ENABLE_DYNAMIC_SHADOWS
+
+vec4 getRelativePosition(in vec4 position)
+{
+	vec2 l = position.xy - CameraPos.xy;
+	vec2 s = l / abs(l);
+	s = (1.0 - s * CameraPos.xy);
+	l /= s;
+	return vec4(l, s);
+}
+
+float getPerspectiveFactor(in vec4 relativePosition)
+{
+	float pDistance = length(relativePosition.xy);
+	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
+	return pFactor;
+}
+
+vec4 applyPerspectiveDistortion(in vec4 position)
+{
+	vec4 l = getRelativePosition(position);
+	float pFactor = getPerspectiveFactor(l);
+	l.xy /= pFactor;
+	position.xy = l.xy * l.zw + CameraPos.xy;
+	position.z *= zPerspectiveBias;
+	return position;
+}
+
 // custom smoothstep implementation because it's not defined in glsl1.2
 // https://docs.gl/sl4/smoothstep
 float mtsmoothstep(in float edge0, in float edge1, in float x)
@@ -107,20 +137,31 @@ void main(void)
 #ifdef ENABLE_DYNAMIC_SHADOWS
 	if (f_shadow_strength > 0.0) {
 		vec3 nNormal = normalize(vNormal);
-		cosLight = dot(nNormal, -v_LightDirection);
+		f_normal_length = length(vNormal);
 
-		// Calculate normal offset scale based on the texel size adjusted for 
-		// curvature of the SM texture. This code must be change together with
-		// getPerspectiveFactor or any light-space transformation.
-		vec3 eyeToVertex = worldPosition - eyePosition + cameraOffset;
-		// Distance from the vertex to the player
-		float distanceToPlayer = length(eyeToVertex - v_LightDirection * dot(eyeToVertex, v_LightDirection)) / f_shadowfar;
-		// perspective factor estimation according to the
-		float perspectiveFactor = distanceToPlayer * xyPerspectiveBias0 + xyPerspectiveBias1;
-		float texelSize = f_shadowfar * perspectiveFactor * perspectiveFactor /
-				(f_textureresolution * xyPerspectiveBias1  - perspectiveFactor * xyPerspectiveBias0);
-		float slopeScale = clamp(pow(1.0 - cosLight*cosLight, 0.5), 0.0, 1.0);
-		normalOffsetScale = texelSize * slopeScale;
+		/* normalOffsetScale is in world coordinates (1/10th of a meter)
+		   z_bias is in light space coordinates */
+		float normalOffsetScale, z_bias;
+		float pFactor = getPerspectiveFactor(getRelativePosition(m_ShadowViewProj * mWorld * inVertexPosition));
+		if (f_normal_length > 0.0) {
+			nNormal = normalize(vNormal);
+			cosLight = dot(nNormal, -v_LightDirection);
+			float sinLight = pow(1 - pow(cosLight, 2.0), 0.5);
+			normalOffsetScale = 0.1 * pFactor * pFactor * sinLight * min(f_shadowfar, 500.0) / 
+					xyPerspectiveBias1 / f_textureresolution;
+			z_bias = 1e3 * sinLight / cosLight * (0.5 + f_textureresolution / 1024.0);
+		}
+		else {
+			nNormal = vec3(0.0);
+			cosLight = clamp(dot(v_LightDirection, normalize(vec3(v_LightDirection.x, 0.0, v_LightDirection.z))), 1e-2, 1.0);
+			float sinLight = pow(1 - pow(cosLight, 2.0), 0.5);
+			normalOffsetScale = 0.0;
+			z_bias = 3.6e3 * sinLight / cosLight;
+		}
+		z_bias *= pFactor * pFactor / f_textureresolution / f_shadowfar;
+
+		shadow_position = applyPerspectiveDistortion(m_ShadowViewProj * mWorld * (inVertexPosition + vec4(normalOffsetScale * nNormal, 0.0))).xyz;
+		shadow_position.z -= z_bias;
 
 		if (f_timeofday < 0.2) {
 			adj_shadow_strength = f_shadow_strength * 0.5 *
@@ -133,7 +174,6 @@ void main(void)
 				mtsmoothstep(0.20, 0.25, f_timeofday) *
 				(1.0 - mtsmoothstep(0.7, 0.8, f_timeofday));
 		}
-		f_normal_length = length(vNormal);
 	}
 #endif
 }

client/shaders/shadow_shaders/pass1_trans_vertex.glsl

@@ -9,24 +9,37 @@ uniform float xyPerspectiveBias0;
 uniform float xyPerspectiveBias1;
 uniform float zPerspectiveBias;
 
-vec4 getPerspectiveFactor(in vec4 shadowPosition)
+vec4 getRelativePosition(in vec4 position)
 {
-	vec2 s = vec2(shadowPosition.x > CameraPos.x ? 1.0 : -1.0, shadowPosition.y > CameraPos.y ? 1.0 : -1.0);
-	vec2 l = s * (shadowPosition.xy - CameraPos.xy) / (1.0 - s * CameraPos.xy);
-	float pDistance = length(l);
-	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
-	l /= pFactor;
-	shadowPosition.xy = CameraPos.xy * (1.0 - l) + s * l;
-	shadowPosition.z *= zPerspectiveBias;
-	return shadowPosition;
+	vec2 l = position.xy - CameraPos.xy;
+	vec2 s = l / abs(l);
+	s = (1.0 - s * CameraPos.xy);
+	l /= s;
+	return vec4(l, s);
 }
 
+float getPerspectiveFactor(in vec4 relativePosition)
+{
+	float pDistance = length(relativePosition.xy);
+	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
+	return pFactor;
+}
+
+vec4 applyPerspectiveDistortion(in vec4 position)
+{
+	vec4 l = getRelativePosition(position);
+	float pFactor = getPerspectiveFactor(l);
+	l.xy /= pFactor;
+	position.xy = l.xy * l.zw + CameraPos.xy;
+	position.z *= zPerspectiveBias;
+	return position;
+}
 
 void main()
 {
 	vec4 pos = LightMVP * gl_Vertex;
 
-	tPos = getPerspectiveFactor(LightMVP * gl_Vertex);
+	tPos = applyPerspectiveDistortion(LightMVP * gl_Vertex);
 
 	gl_Position = vec4(tPos.xyz, 1.0);
 	gl_TexCoord[0].st = gl_MultiTexCoord0.st;

client/shaders/shadow_shaders/pass1_vertex.glsl

@@ -6,24 +6,37 @@ uniform float xyPerspectiveBias0;
 uniform float xyPerspectiveBias1;
 uniform float zPerspectiveBias;
 
-vec4 getPerspectiveFactor(in vec4 shadowPosition)
+vec4 getRelativePosition(in vec4 position)
 {
-	vec2 s = vec2(shadowPosition.x > CameraPos.x ? 1.0 : -1.0, shadowPosition.y > CameraPos.y ? 1.0 : -1.0);
-	vec2 l = s * (shadowPosition.xy - CameraPos.xy) / (1.0 - s * CameraPos.xy);
-	float pDistance = length(l);
-	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
-	l /= pFactor;
-	shadowPosition.xy = CameraPos.xy * (1.0 - l) + s * l;
-	shadowPosition.z *= zPerspectiveBias;
-	return shadowPosition;
+	vec2 l = position.xy - CameraPos.xy;
+	vec2 s = l / abs(l);
+	s = (1.0 - s * CameraPos.xy);
+	l /= s;
+	return vec4(l, s);
 }
 
+float getPerspectiveFactor(in vec4 relativePosition)
+{
+	float pDistance = length(relativePosition.xy);
+	float pFactor = pDistance * xyPerspectiveBias0 + xyPerspectiveBias1;
+	return pFactor;
+}
+
+vec4 applyPerspectiveDistortion(in vec4 position)
+{
+	vec4 l = getRelativePosition(position);
+	float pFactor = getPerspectiveFactor(l);
+	l.xy /= pFactor;
+	position.xy = l.xy * l.zw + CameraPos.xy;
+	position.z *= zPerspectiveBias;
+	return position;
+}
 
 void main()
 {
 	vec4 pos = LightMVP * gl_Vertex;
 
-	tPos = getPerspectiveFactor(pos);
+	tPos = applyPerspectiveDistortion(pos);
 
 	gl_Position = vec4(tPos.xyz, 1.0);
 	gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;

src/client/render/core.cpp

@@ -76,8 +76,11 @@ void RenderingCore::draw(video::SColor _skycolor, bool _show_hud, bool _show_min
 	draw_wield_tool = _draw_wield_tool;
 	draw_crosshair = _draw_crosshair;
 
-	if (shadow_renderer)
+	if (shadow_renderer) {
+		// This is necessary to render shadows for animations correctly
+		smgr->getRootSceneNode()->OnAnimate(device->getTimer()->getTime());
 		shadow_renderer->update();
+	}
 
 	beforeDraw();
 	drawAll();

src/client/shadows/dynamicshadows.h

@@ -69,12 +69,18 @@ public:
 	const core::matrix4 &getFutureProjectionMatrix() const;
 	core::matrix4 getViewProjMatrix();
 
-	/// Gets the light's far value.
+	/// Gets the light's maximum far value, i.e. the shadow boundary
 	f32 getMaxFarValue() const
 	{
 		return farPlane * BS;
 	}
 
+	/// Gets the current far value of the light
+	f32 getFarValue() const
+	{
+		return shadow_frustum.zFar;
+	}
+
 
 	/// Gets the light's color.
 	const video::SColorf &getLightColor() const

src/client/shadows/dynamicshadowsrender.cpp

@@ -143,7 +143,7 @@ size_t ShadowRenderer::getDirectionalLightCount() const
 f32 ShadowRenderer::getMaxShadowFar() const
 {
 	if (!m_light_list.empty()) {
-		float zMax = m_light_list[0].getMaxFarValue();
+		float zMax = m_light_list[0].getFarValue();
 		return zMax;
 	}
 	return 0.0f;
@@ -418,10 +418,6 @@ void ShadowRenderer::renderShadowMap(video::ITexture *target,
 
 		material.BackfaceCulling = false;
 		material.FrontfaceCulling = true;
-		material.PolygonOffsetFactor = 4.0f;
-		material.PolygonOffsetDirection = video::EPO_BACK;
-		//material.PolygonOffsetDepthBias = 1.0f/4.0f;
-		//material.PolygonOffsetSlopeScale = -1.f;
 
 		if (m_shadow_map_colored && pass != scene::ESNRP_SOLID) {
 			material.MaterialType = (video::E_MATERIAL_TYPE) depth_shader_trans;
@@ -431,9 +427,6 @@ void ShadowRenderer::renderShadowMap(video::ITexture *target,
 			material.BlendOperation = video::EBO_MIN;
 		}
 
-		// FIXME: I don't think this is needed here
-		map_node->OnAnimate(m_device->getTimer()->getTime());
-
 		m_driver->setTransform(video::ETS_WORLD,
 				map_node->getAbsoluteTransformation());
 
@@ -479,10 +472,6 @@ void ShadowRenderer::renderShadowObjects(
 
 			current_mat.BackfaceCulling = true;
 			current_mat.FrontfaceCulling = false;
-			current_mat.PolygonOffsetFactor = 1.0f/2048.0f;
-			current_mat.PolygonOffsetDirection = video::EPO_BACK;
-			//current_mat.PolygonOffsetDepthBias = 1.0 * 2.8e-6;
-			//current_mat.PolygonOffsetSlopeScale = -1.f;
 		}
 
 		m_driver->setTransform(video::ETS_WORLD,