From d027b2daf669fc02eece47f3832d63ac18fce1cd Mon Sep 17 00:00:00 2001
From: "C. J. Howard" <cjhoward@cjhoward.org>
Date: Sat, 2 Sep 2023 23:32:00 +0800
Subject: [PATCH] Improve cascaded shadow maps

---
 CMakeLists.txt                                |   1 +
 src/engine/render/passes/material-pass.cpp    |  12 +-
 src/engine/render/passes/material-pass.hpp    |   3 +-
 src/engine/render/renderer.cpp                |   4 +
 src/engine/render/renderer.hpp                |   2 +
 .../cascaded-shadow-map-stage.cpp}            | 238 +++++++++++-------
 .../cascaded-shadow-map-stage.hpp}            |  44 ++--
 src/engine/scene/camera.cpp                   |  12 +-
 src/engine/scene/directional-light.cpp        |  28 +--
 src/engine/scene/directional-light.hpp        |  39 ++-
 src/engine/scene/point-light.cpp              |   2 +-
 src/game/game.cpp                             |   4 -
 src/game/game.hpp                             |   2 -
 .../treadmill-experiment-state.cpp            |   8 +-
 src/game/world.cpp                            |   3 +-
 15 files changed, 238 insertions(+), 164 deletions(-)
 rename src/engine/render/{passes/cascaded-shadow-map-pass.cpp => stages/cascaded-shadow-map-stage.cpp} (59%)
 rename src/engine/render/{passes/cascaded-shadow-map-pass.hpp => stages/cascaded-shadow-map-stage.hpp} (71%)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 21ca183..73e1a79 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,6 @@
 cmake_minimum_required(VERSION 3.25)
 
+
 option(APPLICATION_NAME "Application name" "Antkeeper")
 option(APPLICATION_VERSION "Application version string" "0.0.0")
 option(APPLICATION_AUTHOR "Application author" "C. J. Howard")
diff --git a/src/engine/render/passes/material-pass.cpp b/src/engine/render/passes/material-pass.cpp
index 43e36cb..f570151 100644
--- a/src/engine/render/passes/material-pass.cpp
+++ b/src/engine/render/passes/material-pass.cpp
@@ -394,11 +394,13 @@ void material_pass::evaluate_lighting(const render::context& ctx, std::uint32_t
 					{
 						directional_shadow_maps.resize(directional_shadow_count);
 						directional_shadow_splits.resize(directional_shadow_count);
+						directional_shadow_fade_ranges.resize(directional_shadow_count);
 						directional_shadow_matrices.resize(directional_shadow_count);
 					}
 					
 					directional_shadow_maps[index] = static_cast<const gl::texture_2d*>(directional_light.get_shadow_framebuffer()->get_depth_attachment());
 					directional_shadow_splits[index] = directional_light.get_shadow_cascade_distances();
+					directional_shadow_fade_ranges[index] = directional_light.get_shadow_fade_range();
 					directional_shadow_matrices[index] = directional_light.get_shadow_cascade_matrices();
 				}
 				break;
@@ -681,22 +683,24 @@ void material_pass::build_shader_command_buffer(std::vector<std::function<void()
 		if (auto directional_shadow_maps_var = shader_program.variable("directional_shadow_maps"))
 		{
 			auto directional_shadow_splits_var = shader_program.variable("directional_shadow_splits");
+			auto directional_shadow_fade_ranges_var = shader_program.variable("directional_shadow_fade_ranges");
 			auto directional_shadow_matrices_var = shader_program.variable("directional_shadow_matrices");
 			
-			if (directional_shadow_maps_var && directional_shadow_splits_var && directional_shadow_matrices_var)
+			if (directional_shadow_maps_var && directional_shadow_splits_var && directional_shadow_fade_ranges_var && directional_shadow_matrices_var)
 			{
 				command_buffer.emplace_back
 				(
-					[&, directional_shadow_maps_var, directional_shadow_splits_var, directional_shadow_matrices_var]()
+					[&, directional_shadow_maps_var, directional_shadow_splits_var, directional_shadow_fade_ranges_var, directional_shadow_matrices_var]()
 					{
 						directional_shadow_maps_var->update(std::span<const gl::texture_2d* const>{directional_shadow_maps.data(), directional_shadow_count});
 						
 						std::size_t offset = 0;
 						for (std::size_t i = 0; i < directional_shadow_count; ++i)
 						{
-							directional_shadow_splits_var->update(directional_shadow_splits[i], offset * 4);
+							directional_shadow_splits_var->update(directional_shadow_splits[i], i);
+							directional_shadow_fade_ranges_var->update(directional_shadow_fade_ranges[i], i);
 							directional_shadow_matrices_var->update(directional_shadow_matrices[i], offset);
-							offset += directional_shadow_splits[i].size();
+							offset += directional_shadow_matrices[i].size();
 						}
 					}
 				);
diff --git a/src/engine/render/passes/material-pass.hpp b/src/engine/render/passes/material-pass.hpp
index b9abeba..41bfe28 100644
--- a/src/engine/render/passes/material-pass.hpp
+++ b/src/engine/render/passes/material-pass.hpp
@@ -115,7 +115,8 @@ private:
 	
 	// Directional shadows
 	std::vector<const gl::texture_2d*> directional_shadow_maps;
-	std::vector<std::span<const float>> directional_shadow_splits;
+	std::vector<math::fvec4> directional_shadow_splits;
+	std::vector<float> directional_shadow_fade_ranges;
 	std::vector<std::span<const math::fmat4>> directional_shadow_matrices;
 	std::size_t directional_shadow_count;
 	
diff --git a/src/engine/render/renderer.cpp b/src/engine/render/renderer.cpp
index 8f69341..920dc0a 100644
--- a/src/engine/render/renderer.cpp
+++ b/src/engine/render/renderer.cpp
@@ -41,6 +41,7 @@ namespace render {
 renderer::renderer(gl::rasterizer& rasterizer, ::resource_manager& resource_manager)
 {
 	m_light_probe_stage = std::make_unique<render::light_probe_stage>(rasterizer, resource_manager);
+	m_cascaded_shadow_map_stage = std::make_unique<render::cascaded_shadow_map_stage>(rasterizer, resource_manager);
 	m_culling_stage = std::make_unique<render::culling_stage>();
 	m_queue_stage = std::make_unique<render::queue_stage>();
 }
@@ -78,6 +79,9 @@ void renderer::render(float t, float dt, float alpha, scene::collection& collect
 		m_ctx.objects.clear();
 		m_ctx.operations.clear();
 		
+		// Execute cascaded shadow map stage
+		m_cascaded_shadow_map_stage->execute(m_ctx);
+		
 		// Execute culling stage
 		m_culling_stage->execute(m_ctx);
 		
diff --git a/src/engine/render/renderer.hpp b/src/engine/render/renderer.hpp
index 2eafff2..68cc496 100644
--- a/src/engine/render/renderer.hpp
+++ b/src/engine/render/renderer.hpp
@@ -23,6 +23,7 @@
 #include <engine/render/context.hpp>
 #include <engine/render/stages/culling-stage.hpp>
 #include <engine/render/stages/queue-stage.hpp>
+#include <engine/render/stages/cascaded-shadow-map-stage.hpp>
 #include <engine/render/stages/light-probe-stage.hpp>
 #include <engine/scene/collection.hpp>
 #include <engine/gl/rasterizer.hpp>
@@ -58,6 +59,7 @@ public:
 private:
 	render::context m_ctx;
 	std::unique_ptr<render::light_probe_stage> m_light_probe_stage;
+	std::unique_ptr<render::cascaded_shadow_map_stage> m_cascaded_shadow_map_stage;
 	std::unique_ptr<render::culling_stage> m_culling_stage;
 	std::unique_ptr<render::queue_stage> m_queue_stage;
 };
diff --git a/src/engine/render/passes/cascaded-shadow-map-pass.cpp b/src/engine/render/stages/cascaded-shadow-map-stage.cpp
similarity index 59%
rename from src/engine/render/passes/cascaded-shadow-map-pass.cpp
rename to src/engine/render/stages/cascaded-shadow-map-stage.cpp
index f508f3b..12d8a5e 100644
--- a/src/engine/render/passes/cascaded-shadow-map-pass.cpp
+++ b/src/engine/render/stages/cascaded-shadow-map-stage.cpp
@@ -17,7 +17,7 @@
  * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <engine/render/passes/cascaded-shadow-map-pass.hpp>
+#include <engine/render/stages/cascaded-shadow-map-stage.hpp>
 #include <engine/resources/resource-manager.hpp>
 #include <engine/gl/rasterizer.hpp>
 #include <engine/gl/framebuffer.hpp>
@@ -26,7 +26,6 @@
 #include <engine/render/context.hpp>
 #include <engine/render/material.hpp>
 #include <engine/render/vertex-attribute.hpp>
-#include <engine/gl/shader-template.hpp>
 #include <engine/scene/camera.hpp>
 #include <engine/scene/collection.hpp>
 #include <engine/scene/light.hpp>
@@ -36,16 +35,19 @@
 #include <engine/math/matrix.hpp>
 #include <engine/math/quaternion.hpp>
 #include <engine/math/projection.hpp>
+#include <engine/geom/primitives/view-frustum.hpp>
 #include <cmath>
 #include <glad/glad.h>
+#include <algorithm>
 #include <execution>
+#include <mutex>
 
 namespace render {
 
 static bool operation_compare(const render::operation* a, const render::operation* b);
 
-cascaded_shadow_map_pass::cascaded_shadow_map_pass(gl::rasterizer* rasterizer, resource_manager* resource_manager):
-	pass(rasterizer, nullptr)
+cascaded_shadow_map_stage::cascaded_shadow_map_stage(gl::rasterizer& rasterizer, ::resource_manager& resource_manager):
+	m_rasterizer(&rasterizer)
 {
 	// Init shader template definitions
 	m_shader_template_definitions["VERTEX_POSITION"]    = std::to_string(vertex_attribute::position);
@@ -61,7 +63,7 @@ cascaded_shadow_map_pass::cascaded_shadow_map_pass(gl::rasterizer* rasterizer, r
 	// Static mesh shader
 	{
 		// Load static mesh shader template
-		m_static_mesh_shader_template = resource_manager->load<gl::shader_template>("shadow-cascade-static-mesh.glsl");
+		m_static_mesh_shader_template = resource_manager.load<gl::shader_template>("shadow-cascade-static-mesh.glsl");
 		
 		// Build static mesh shader program
 		rebuild_static_mesh_shader_program();
@@ -70,14 +72,14 @@ cascaded_shadow_map_pass::cascaded_shadow_map_pass(gl::rasterizer* rasterizer, r
 	// Skeletal mesh shader
 	{
 		// Load skeletal mesh shader template
-		m_skeletal_mesh_shader_template = resource_manager->load<gl::shader_template>("shadow-cascade-skeletal-mesh.glsl");
+		m_skeletal_mesh_shader_template = resource_manager.load<gl::shader_template>("shadow-cascade-skeletal-mesh.glsl");
 		
 		// Build static mesh shader program
 		rebuild_skeletal_mesh_shader_program();
 	}
 }
 
-void cascaded_shadow_map_pass::render(render::context& ctx)
+void cascaded_shadow_map_stage::execute(render::context& ctx)
 {
 	// For each light
 	const auto& lights = ctx.collection->get_objects(scene::light::object_type_id);
@@ -110,11 +112,13 @@ void cascaded_shadow_map_pass::render(render::context& ctx)
 		}
 		
 		// Render shadow atlas
-		render_atlas(directional_light, ctx);
+		render_shadow_atlas(ctx, directional_light);
 	}
+	
+	ctx.operations.clear();
 }
 
-void cascaded_shadow_map_pass::set_max_bone_count(std::size_t bone_count)
+void cascaded_shadow_map_stage::set_max_bone_count(std::size_t bone_count)
 {
 	if (m_max_bone_count != bone_count)
 	{
@@ -128,7 +132,69 @@ void cascaded_shadow_map_pass::set_max_bone_count(std::size_t bone_count)
 	}
 }
 
-void cascaded_shadow_map_pass::render_atlas(scene::directional_light& light, render::context& ctx)
+void cascaded_shadow_map_stage::queue(render::context& ctx, scene::directional_light& light, const math::fmat4& light_view_projection)
+{
+	// Clear pre-existing render operations
+	ctx.operations.clear();
+	
+	// Combine camera and light layer masks
+	const auto camera_light_layer_mask = ctx.camera->get_layer_mask() & light.get_layer_mask();
+	
+	// Build light view frustum from light view projection matrix
+	const geom::view_frustum<float> light_view_frustum(light_view_projection);
+	
+	// Tests whether a box is completely outside a plane
+	auto box_outside_plane = [](const geom::box<float>& box, const geom::plane<float>& plane) -> bool
+	{
+		const math::fvec3 p =
+		{
+			(plane.normal.x() > 0.0f) ? box.max.x() : box.min.x(),
+			(plane.normal.y() > 0.0f) ? box.max.y() : box.min.y(),
+			(plane.normal.z() > 0.0f) ? box.max.z() : box.min.z()
+		};
+		
+		return plane.distance(p) < 0.0f;
+	};
+	
+	// For each object in the scene collection
+	const auto& objects = ctx.collection->get_objects();
+	std::for_each
+	(
+		std::execution::seq,
+		std::begin(objects),
+		std::end(objects),
+		[&](scene::object_base* object)
+		{
+			// Cull object if it doesn't share a common layer with the camera and light
+			if (!(object->get_layer_mask() & camera_light_layer_mask))
+			{
+				return;
+			}
+			
+			// Ignore cameras and lights
+			if (object->get_object_type_id() == scene::camera::object_type_id || object->get_object_type_id() == scene::light::object_type_id)
+			{
+				return;
+			}
+			
+			// Cull object if it's outside of the light view frustum (excluding near plane [reverse-z, so far=near])
+			const auto& object_bounds = object->get_bounds();
+			if (box_outside_plane(object_bounds, light_view_frustum.left()) ||
+				box_outside_plane(object_bounds, light_view_frustum.right()) ||
+				box_outside_plane(object_bounds, light_view_frustum.bottom()) ||
+				box_outside_plane(object_bounds, light_view_frustum.top()) ||
+				box_outside_plane(object_bounds, light_view_frustum.near()))
+			{
+				return;
+			}
+			
+			// Add object render operations to render context
+			object->render(ctx);
+		}
+	);
+}
+
+void cascaded_shadow_map_stage::render_shadow_atlas(render::context& ctx, scene::directional_light& light)
 {
 	// Disable blending
 	glDisable(GL_BLEND);
@@ -138,114 +204,98 @@ void cascaded_shadow_map_pass::render_atlas(scene::directional_light& light, ren
 	glDepthFunc(GL_GREATER);
 	glDepthMask(GL_TRUE);
 	
+	// Disable depth clipping (enable "pancaking")
+	glEnable(GL_DEPTH_CLAMP);
+	
 	// Enable back-face culling
 	glEnable(GL_CULL_FACE);
 	glCullFace(GL_BACK);
 	bool two_sided = false;
 	
 	// Bind and clear shadow atlas framebuffer
-	rasterizer->use_framebuffer(*light.get_shadow_framebuffer());
-	rasterizer->clear_framebuffer(false, true, false);
-	
-	// Get light layer mask
-	const auto light_layer_mask = light.get_layer_mask();
+	m_rasterizer->use_framebuffer(*light.get_shadow_framebuffer());
+	m_rasterizer->clear_framebuffer(false, true, false);
 	
 	// Get camera
 	const scene::camera& camera = *ctx.camera;
 	
-	// Calculate distance to shadow cascade depth clipping planes
-	const auto shadow_clip_near = camera.get_clip_near();
-	const auto shadow_clip_far = camera.get_clip_near() + light.get_shadow_distance();
-	
 	// Get light shadow cascade distances and matrices
 	const auto cascade_count = light.get_shadow_cascade_count();
-	const auto cascade_distances = light.get_shadow_cascade_distances();
+	auto& cascade_distances = light.get_shadow_cascade_distances();
 	const auto cascade_matrices = light.get_shadow_cascade_matrices();
 	
 	// Calculate cascade far clipping plane distances
-	cascade_distances[cascade_count - 1] = shadow_clip_far;
+	cascade_distances[cascade_count - 1] = light.get_shadow_max_distance();
 	for (unsigned int i = 0; i < cascade_count - 1; ++i)
 	{
 		const float weight = static_cast<float>(i + 1) / static_cast<float>(cascade_count);
 		
 		// Calculate linear and logarithmic split distances
-		const float linear_distance = math::lerp(shadow_clip_near, shadow_clip_far, weight);
-		const float log_distance = math::log_lerp(shadow_clip_near, shadow_clip_far, weight);
+		const float linear_distance = math::lerp(camera.get_clip_near(), camera.get_clip_near() + light.get_shadow_max_distance(), weight);
+		const float log_distance = math::log_lerp(camera.get_clip_near(), camera.get_clip_near() + light.get_shadow_max_distance(), weight);
 		
 		// Interpolate between linear and logarithmic split distances
 		cascade_distances[i] = math::lerp(linear_distance, log_distance, light.get_shadow_cascade_distribution());
 	}
 	
-	// Calculate viewports for each shadow map
-	const int shadow_map_resolution = static_cast<int>(light.get_shadow_framebuffer()->get_depth_attachment()->get_width());
-	const int cascade_resolution = shadow_map_resolution >> 1;
-	math::ivec4 shadow_map_viewports[4];
-	for (int i = 0; i < 4; ++i)
-	{
-		int x = i % 2;
-		int y = i / 2;
-		
-		math::ivec4& viewport = shadow_map_viewports[i];
-		viewport[0] = x * cascade_resolution;
-		viewport[1] = y * cascade_resolution;
-		viewport[2] = cascade_resolution;
-		viewport[3] = cascade_resolution;
-	}
+	// Determine resolution of shadow atlas and cascades
+	const auto atlas_resolution = static_cast<int>(light.get_shadow_framebuffer()->get_depth_attachment()->get_width());
+	const auto cascade_resolution = atlas_resolution >> 1;
 	
 	// Sort render operations
 	std::sort(std::execution::par_unseq, ctx.operations.begin(), ctx.operations.end(), operation_compare);
 	
 	gl::shader_program* active_shader_program = nullptr;
 	
-	// Precalculate frustum minimal bounding sphere terms
-	const auto k = std::sqrt(1.0f + camera.get_aspect_ratio() * camera.get_aspect_ratio()) * std::tan(camera.get_vertical_fov() * 0.5f);
-	const auto k2 = k * k;
-	const auto k4 = k2 * k2;
-	
 	for (unsigned int i = 0; i < cascade_count; ++i)
 	{
-		// Set viewport for this shadow map
-		const math::ivec4& viewport = shadow_map_viewports[i];
-		rasterizer->set_viewport(viewport[0], viewport[1], viewport[2], viewport[3]);
+		// Get distances to near and far clipping planes of camera subfrustum
+		const auto subfrustum_near = i ? cascade_distances[i - 1] : camera.get_clip_near();
+		const auto subfrustum_far = cascade_distances[i];
 		
-		// Find minimal bounding sphere of subfrustum in view-space
-		// @see https://lxjk.github.io/2017/04/15/Calculate-Minimal-Bounding-Sphere-of-Frustum.html
-		geom::sphere<float> subfrustum_bounds;
-		{
-			// Get subfrustum near and far distances
-			const auto n = (i) ? cascade_distances[i - 1] : camera.get_clip_near();
-			const auto f = cascade_distances[i];
-			
-			if (k2 >= (f - n) / (f + n))
-			{
-				subfrustum_bounds.center = {0, 0, -f};
-				subfrustum_bounds.radius = f * k;
-			}
-			else
-			{
-				subfrustum_bounds.center = {0, 0, -0.5f * (f + n) * (1.0f + k2)};
-				subfrustum_bounds.radius = 0.5f * std::sqrt((k4 + 2.0f * k2 + 1.0f) * (f * f + n * n) + 2.0f * f * (k4 - 1.0f) * n);
-			}
-		}
+		// Find centroid of camera subfrustum
+		const auto subfrustum_centroid = camera.get_translation() + camera.get_forward() * ((subfrustum_near + subfrustum_far) * 0.5f);
 		
-		// Transform subfrustum bounds into world-space
-		subfrustum_bounds.center = camera.get_translation() + camera.get_rotation() * subfrustum_bounds.center;
+		// Construct light view matrix
+		const auto light_view = math::look_at_rh(subfrustum_centroid, subfrustum_centroid + light.get_direction(), light.get_rotation() * math::fvec3{0, 1, 0});
 		
-		// Discretize view-space subfrustum bounds
-		const auto texel_scale = static_cast<float>(cascade_resolution) / (subfrustum_bounds.radius * 2.0f);
-		subfrustum_bounds.center = math::conjugate(light.get_rotation()) * subfrustum_bounds.center;
-		subfrustum_bounds.center = math::floor(subfrustum_bounds.center * texel_scale) / texel_scale;
-		subfrustum_bounds.center = light.get_rotation() * subfrustum_bounds.center;
+		// Construct subfrustum inverse view-projection matrix
+		const auto [subfrustum_projection, subfrustum_inv_projection] = math::perspective_half_z_inv(camera.get_vertical_fov(), camera.get_aspect_ratio(), subfrustum_far, subfrustum_near);
+		const auto subfrustum_inv_view_projection = camera.get_inv_view() * subfrustum_inv_projection;
 		
-		// Construct light view matrix
-		const auto light_view = math::look_at_rh(subfrustum_bounds.center, subfrustum_bounds.center + light.get_direction(), light.get_rotation() * math::fvec3{0, 1, 0});
+		// Construct matrix which transforms clip space coordinates to light view space
+		const auto ndc_to_light_view = light_view * subfrustum_inv_view_projection;
 		
-		// Construct light projection matrix (reversed depth)
+		// Construct AABB containing subfrustum corners in light view space
+		geom::box<float> light_projection_bounds = {math::fvec3::infinity(), -math::fvec3::infinity()};
+		for (std::size_t j = 0; j < 8; ++j)
+		{
+			// Reverse half z clip-space coordinates of a cube
+			constexpr math::fvec4 ndc_cube[8] =
+			{
+				{-1, -1, 1, 1}, // NBL
+				{ 1, -1, 1, 1}, // NBR
+				{-1,  1, 1, 1}, // NTL
+				{ 1,  1, 1, 1}, // NTR
+				{-1, -1, 0, 1}, // FBL
+				{ 1, -1, 0, 1}, // FBR
+				{-1,  1, 0, 1}, // FTL
+				{ 1,  1, 0, 1}  // FTR
+			};
+			
+			// Find light view space coordinates of subfrustum corner
+			const auto corner = ndc_to_light_view * ndc_cube[j];
+			
+			// Expand light projection bounds to contain corner
+			light_projection_bounds.extend(math::fvec3(corner) / corner[3]);
+		}
+		
+		// Construct light projection matrix
 		const auto light_projection = math::ortho_half_z
 		(
-			-subfrustum_bounds.radius, subfrustum_bounds.radius,
-			-subfrustum_bounds.radius, subfrustum_bounds.radius,
-			subfrustum_bounds.radius, -subfrustum_bounds.radius
+			light_projection_bounds.min.x(), light_projection_bounds.max.x(),
+			light_projection_bounds.min.y(), light_projection_bounds.max.y(),
+			-light_projection_bounds.min.z(), -light_projection_bounds.max.z()
 		);
 		
 		// Construct light view-projection matrix
@@ -254,14 +304,21 @@ void cascaded_shadow_map_pass::render_atlas(scene::directional_light& light, ren
 		// Update world-space to cascade texture-space transformation matrix
 		cascade_matrices[i] = light.get_shadow_scale_bias_matrices()[i] * light_view_projection;
 		
+		// Queue render operations
+		queue(ctx, light, light_view_projection);
+		if (ctx.operations.empty())
+		{
+			continue;
+		}
+		
+		// Set viewport for this cascade
+		const auto viewport_x = static_cast<int>(i % 2) * cascade_resolution;
+		const auto viewport_y = static_cast<int>(i >> 1) * cascade_resolution;
+		m_rasterizer->set_viewport(viewport_x, viewport_y, cascade_resolution, cascade_resolution);
+		
+		// Render geometry
 		for (const render::operation* operation: ctx.operations)
 		{
-			// Skip operations which don't share any layers with the shadow-casting light
-			if (!(operation->layer_mask & light_layer_mask))
-			{
-				continue;
-			}
-			
 			const render::material* material = operation->material.get();
 			if (material)
 			{
@@ -291,11 +348,11 @@ void cascaded_shadow_map_pass::render_atlas(scene::directional_light& light, ren
 			if (active_shader_program != shader_program)
 			{
 				active_shader_program = shader_program;
-				rasterizer->use_program(*active_shader_program);
+				m_rasterizer->use_program(*active_shader_program);
 			}
 			
 			// Calculate model-view-projection matrix
-			math::fmat4 model_view_projection = light_view_projection * operation->transform;
+			const auto model_view_projection = light_view_projection * operation->transform;
 			
 			// Upload operation-dependent parameters to shader program
 			if (active_shader_program == m_static_mesh_shader_program.get())
@@ -309,12 +366,15 @@ void cascaded_shadow_map_pass::render_atlas(scene::directional_light& light, ren
 			}
 
 			// Draw geometry
-			rasterizer->draw_arrays(*operation->vertex_array, operation->drawing_mode, operation->start_index, operation->index_count);
+			m_rasterizer->draw_arrays(*operation->vertex_array, operation->drawing_mode, operation->start_index, operation->index_count);
 		}
 	}
+	
+	// Re-enable depth clipping (disable "pancaking")
+	glDisable(GL_DEPTH_CLAMP);
 }
 
-void cascaded_shadow_map_pass::rebuild_static_mesh_shader_program()
+void cascaded_shadow_map_stage::rebuild_static_mesh_shader_program()
 {
 	m_static_mesh_shader_program = m_static_mesh_shader_template->build(m_shader_template_definitions);
 	if (!m_static_mesh_shader_program->linked())
@@ -330,7 +390,7 @@ void cascaded_shadow_map_pass::rebuild_static_mesh_shader_program()
 	}
 }
 
-void cascaded_shadow_map_pass::rebuild_skeletal_mesh_shader_program()
+void cascaded_shadow_map_stage::rebuild_skeletal_mesh_shader_program()
 {
 	m_skeletal_mesh_shader_program = m_skeletal_mesh_shader_template->build(m_shader_template_definitions);
 	if (!m_skeletal_mesh_shader_program->linked())
diff --git a/src/engine/render/passes/cascaded-shadow-map-pass.hpp b/src/engine/render/stages/cascaded-shadow-map-stage.hpp
similarity index 71%
rename from src/engine/render/passes/cascaded-shadow-map-pass.hpp
rename to src/engine/render/stages/cascaded-shadow-map-stage.hpp
index 5fcc63d..38deeca 100644
--- a/src/engine/render/passes/cascaded-shadow-map-pass.hpp
+++ b/src/engine/render/stages/cascaded-shadow-map-stage.hpp
@@ -17,44 +17,37 @@
  * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_PASS_HPP
-#define ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_PASS_HPP
+#ifndef ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_STAGE_HPP
+#define ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_STAGE_HPP
 
-#include <engine/render/pass.hpp>
-#include <engine/math/vector.hpp>
-#include <engine/scene/directional-light.hpp>
+#include <engine/render/stage.hpp>
+#include <engine/gl/shader-template.hpp>
 #include <engine/gl/shader-program.hpp>
 #include <engine/gl/shader-variable.hpp>
+#include <engine/gl/rasterizer.hpp>
+#include <engine/scene/directional-light.hpp>
+#include <engine/resources/resource-manager.hpp>
 #include <memory>
 #include <string>
 #include <unordered_map>
 
-class resource_manager;
-
 namespace render {
 
 /**
  * Renders cascaded shadow maps for directional lights.
  */
-class cascaded_shadow_map_pass: public pass
+class cascaded_shadow_map_stage: public stage
 {
 public:
 	/**
-	 * Constructs a shadow map pass.
+	 * Constructs a cascaded shadow map stage.
 	 *
-	 * @param rasterizer Rasterizer.
-	 * @param framebuffer Shadow map framebuffer.
-	 * @param resource_manage Resource manager.
+	 * @param rasterizer GL rasterizer.
+	 * @param resource_manager Resource manager for loading shader templates.
 	 */
-	cascaded_shadow_map_pass(gl::rasterizer* rasterizer, resource_manager* resource_manager);
+	cascaded_shadow_map_stage(gl::rasterizer& rasterizer, ::resource_manager& resource_manager);
 	
-	/**
-	 * Renders shadow maps for a single camera.
-	 *
-	 * @param ctx Render context.
-	 * @param queue Render queue.
-	 */
-	void render(render::context& ctx) override;
+	void execute(render::context& ctx) override;
 	
 	/**
 	 * Sets the maximum bone count for shadow-casting skeletal meshes.
@@ -72,13 +65,18 @@ public:
 	}
 
 private:
+	/**
+	 * Queues render operations of objects that may cast shadows visible to the current camera.
+	 */
+	void queue(render::context& ctx, scene::directional_light& light, const math::fmat4& light_view_projection);
+	
 	/**
 	 * Renders an atlas of cascaded shadow maps for a single directional light.
 	 *
 	 * @param light Shadow-casting directional light.
 	 * @param ctx Render context.
 	 */
-	void render_atlas(scene::directional_light& light, render::context& ctx);
+	void render_shadow_atlas(render::context& ctx, scene::directional_light& light);
 	
 	/// Rebuilds the shader program for static meshes.
 	void rebuild_static_mesh_shader_program();
@@ -86,6 +84,8 @@ private:
 	/// Rebuilds the shader program for skeletal meshes.
 	void rebuild_skeletal_mesh_shader_program();
 	
+	gl::rasterizer* m_rasterizer;
+	
 	std::size_t m_max_bone_count{64};
 	
 	std::unordered_map<std::string, std::string> m_shader_template_definitions;
@@ -102,4 +102,4 @@ private:
 
 } // namespace render
 
-#endif // ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_PASS_HPP
+#endif // ANTKEEPER_RENDER_CASCADED_SHADOW_MAP_STAGE_HPP
diff --git a/src/engine/scene/camera.cpp b/src/engine/scene/camera.cpp
index a5d051d..3576653 100644
--- a/src/engine/scene/camera.cpp
+++ b/src/engine/scene/camera.cpp
@@ -27,8 +27,8 @@ geom::ray<float, 3> camera::pick(const math::fvec2& ndc) const
 {
 	const auto near = m_inv_view_projection * math::fvec4{ndc[0], ndc[1], 1.0f, 1.0f};
 	const auto far = m_inv_view_projection * math::fvec4{ndc[0], ndc[1], 0.0f, 1.0f};
-	const auto origin = math::fvec3{near[0], near[1], near[2]} / near[3];
-	const auto direction = math::normalize(math::fvec3{far[0], far[1], far[2]} / far[3] - origin);
+	const auto origin = math::fvec3(near) / near[3];
+	const auto direction = math::normalize(math::fvec3(far) / far[3] - origin);
 	
 	return {origin, direction};
 }
@@ -36,12 +36,10 @@ geom::ray<float, 3> camera::pick(const math::fvec2& ndc) const
 math::fvec3 camera::project(const math::fvec3& object, const math::fvec4& viewport) const
 {
 	math::fvec4 result = m_view_projection * math::fvec4{object[0], object[1], object[2], 1.0f};
-	result[0] = (result[0] / result[3]) * 0.5f + 0.5f;
-	result[1] = (result[1] / result[3]) * 0.5f + 0.5f;
-	result[2] = (result[2] / result[3]) * 0.5f + 0.5f;
+	result /= result[3];
 	
-	result[0] = result[0] * viewport[2] + viewport[0];
-	result[1] = result[1] * viewport[3] + viewport[1];
+	result.x() = result.x() * viewport[2] + viewport[0];
+	result.y() = result.y() * viewport[3] + viewport[1];
 	
 	return math::fvec3(result);
 }
diff --git a/src/engine/scene/directional-light.cpp b/src/engine/scene/directional-light.cpp
index 77744e1..668225c 100644
--- a/src/engine/scene/directional-light.cpp
+++ b/src/engine/scene/directional-light.cpp
@@ -21,10 +21,7 @@
 
 namespace scene {
 
-directional_light::directional_light():
-	m_shadow_cascade_distances(m_shadow_cascade_count),
-	m_shadow_cascade_matrices(m_shadow_cascade_count),
-	m_shadow_scale_bias_matrices(m_shadow_cascade_count)
+directional_light::directional_light()
 {
 	set_shadow_bias(m_shadow_bias);
 	update_shadow_cascade_distances();
@@ -54,19 +51,21 @@ void directional_light::set_shadow_bias(float bias) noexcept
 void directional_light::set_shadow_cascade_count(unsigned int count) noexcept
 {
 	m_shadow_cascade_count = std::min(std::max(count, 1u), 4u);
-	m_shadow_cascade_distances.resize(m_shadow_cascade_count);
-	m_shadow_cascade_matrices.resize(m_shadow_cascade_count);
-	m_shadow_scale_bias_matrices.resize(m_shadow_cascade_count);
 	update_shadow_scale_bias_matrices();
 	update_shadow_cascade_distances();
 }
 
-void directional_light::set_shadow_distance(float distance) noexcept
+void directional_light::set_shadow_max_distance(float distance) noexcept
 {
-	m_shadow_distance = distance;
+	m_shadow_max_distance = distance;
 	update_shadow_cascade_distances();
 }
 
+void directional_light::set_shadow_fade_range(float range) noexcept
+{
+	m_shadow_fade_range = range;
+}
+
 void directional_light::set_shadow_cascade_distribution(float weight) noexcept
 {
 	m_shadow_cascade_distribution = weight;
@@ -90,10 +89,7 @@ void directional_light::illuminance_updated()
 
 void directional_light::update_shadow_scale_bias_matrices()
 {
-	// Construct shadow scale-bias matrix (depth range `[-1, 1]`)
-	// auto m = math::translate(math::fvec3{0.5f, 0.5f, 0.5f + m_shadow_bias}) * math::scale(math::fvec3{0.5f, 0.5f, 0.5f});
-	
-	// Construct shadow scale-bias matrix (depth range `[0, 1]`)
+	// Transform coordinate range from `[-1, 1]` to `[0, 1]` and apply shadow bias
 	auto m = math::translate(math::fvec3{0.5f, 0.5f, m_shadow_bias}) * math::scale(math::fvec3{0.5f, 0.5f, 1.0f});
 	
 	// Apply cascade scale
@@ -113,14 +109,14 @@ void directional_light::update_shadow_cascade_distances()
 		return;
 	}
 	
-	m_shadow_cascade_distances[m_shadow_cascade_count - 1] = m_shadow_distance;
+	m_shadow_cascade_distances[m_shadow_cascade_count - 1] = m_shadow_max_distance;
 	for (unsigned int i = 0; i < m_shadow_cascade_count - 1; ++i)
 	{
 		const auto weight = static_cast<float>(i + 1) / static_cast<float>(m_shadow_cascade_count);
 		
 		// Calculate linear and logarithmic distribution distances
-		const auto linear_distance = m_shadow_distance * weight;
-		// const auto log_distance = math::log_lerp(0.0f, m_shadow_distance, weight);
+		const auto linear_distance = m_shadow_max_distance * weight;
+		// const auto log_distance = math::log_lerp(0.0f, m_shadow_max_distance, weight);
 		
 		// Interpolate between linear and logarithmic distribution distances
 		// cascade_distances[i] = math::lerp(linear_distance, log_distance, light.get_shadow_cascade_distribution());
diff --git a/src/engine/scene/directional-light.hpp b/src/engine/scene/directional-light.hpp
index 45bdacc..fa8c982 100644
--- a/src/engine/scene/directional-light.hpp
+++ b/src/engine/scene/directional-light.hpp
@@ -24,7 +24,6 @@
 #include <engine/gl/texture-2d.hpp>
 #include <engine/math/vector.hpp>
 #include <memory>
-#include <vector>
 #include <span>
 
 namespace scene {
@@ -136,11 +135,18 @@ public:
 	void set_shadow_cascade_count(unsigned int count) noexcept;
 	
 	/**
-	 * Sets the distance from the camera up to which shadows are visible.
+	 * Sets the maximum distance from a camera's near clipping plane up to which shadows are visible.
 	 *
-	 * @param distance Shadow distance.
+	 * @param distance Maximum shadow distance.
 	 */
-	void set_shadow_distance(float distance) noexcept;
+	void set_shadow_max_distance(float distance) noexcept;
+	
+	/**
+	 * Sets the distance from the maximum shadow distance at which shadows will begin to fade out.
+	 *
+	 * @param range Shadow fade range.
+	 */
+	void set_shadow_fade_range(float range) noexcept;
 	
 	/**
 	 * Sets the shadow cascade distribution.
@@ -173,10 +179,16 @@ public:
 		return m_shadow_cascade_count;
 	}
 	
-	/// Returns the distance from the camera up to which shadows are visible.
-	[[nodiscard]] inline constexpr float get_shadow_distance() const noexcept
+	/// Returns the maximum distance from a camera's near clipping plane up to which shadows are visible.
+	[[nodiscard]] inline constexpr float get_shadow_max_distance() const noexcept
+	{
+		return m_shadow_max_distance;
+	}
+	
+	/// Returns the distance from the maximum shadow distance at which shadows will begin to fade out.
+	[[nodiscard]] inline constexpr float get_shadow_fade_range() const noexcept
 	{
-		return m_shadow_distance;
+		return m_shadow_fade_range;
 	}
 	
 	/// Returns the shadow cascade distribution weight.
@@ -187,11 +199,11 @@ public:
 	
 	/// Returns the array of shadow cascade far clipping plane distances.
 	/// @{
-	[[nodiscard]] inline constexpr std::span<const float> get_shadow_cascade_distances() const noexcept
+	[[nodiscard]] inline constexpr const math::fvec4& get_shadow_cascade_distances() const noexcept
 	{
 		return m_shadow_cascade_distances;
 	}
-	[[nodiscard]] inline constexpr std::span<float> get_shadow_cascade_distances() noexcept
+	[[nodiscard]] inline constexpr math::fvec4& get_shadow_cascade_distances() noexcept
 	{
 		return m_shadow_cascade_distances;
 	}
@@ -233,11 +245,12 @@ private:
 	std::shared_ptr<gl::framebuffer> m_shadow_framebuffer{nullptr};
 	float m_shadow_bias{0.005f};
 	unsigned int m_shadow_cascade_count{4};
-	float m_shadow_distance{1000.0f};
+	float m_shadow_max_distance{100.0f};
+	float m_shadow_fade_range{0.0f};
 	float m_shadow_cascade_distribution{0.8f};
-	std::vector<float> m_shadow_cascade_distances;
-	std::vector<math::fmat4> m_shadow_cascade_matrices;
-	std::vector<math::fmat4> m_shadow_scale_bias_matrices;
+	math::fvec4 m_shadow_cascade_distances;
+	math::fmat4 m_shadow_cascade_matrices[4];
+	math::fmat4 m_shadow_scale_bias_matrices[4];
 };
 
 } // namespace scene
diff --git a/src/engine/scene/point-light.cpp b/src/engine/scene/point-light.cpp
index 018ad61..d8b4485 100644
--- a/src/engine/scene/point-light.cpp
+++ b/src/engine/scene/point-light.cpp
@@ -26,7 +26,7 @@ void point_light::color_updated()
 	m_colored_luminous_flux = get_color() * m_luminous_flux;
 }
 
-void point_light::luminous_flux_updated()
+void point_light::luminous_flux_updated() noexcept
 {
 	m_colored_luminous_flux = get_color() * m_luminous_flux;
 }
diff --git a/src/game/game.cpp b/src/game/game.cpp
index a4ddd9b..87f6d1b 100644
--- a/src/game/game.cpp
+++ b/src/game/game.cpp
@@ -85,7 +85,6 @@
 #include <engine/render/passes/material-pass.hpp>
 #include <engine/render/passes/outline-pass.hpp>
 #include <engine/render/passes/resample-pass.hpp>
-#include <engine/render/passes/cascaded-shadow-map-pass.hpp>
 #include <engine/render/passes/sky-pass.hpp>
 #include <engine/render/renderer.hpp>
 #include <engine/render/vertex-attribute.hpp>
@@ -735,8 +734,6 @@ void game::setup_rendering()
 	
 	// Setup surface compositor
 	{
-		surface_cascaded_shadow_map_pass = std::make_unique<render::cascaded_shadow_map_pass>(window->get_rasterizer(), resource_manager.get());
-		
 		surface_clear_pass = std::make_unique<render::clear_pass>(window->get_rasterizer(), hdr_framebuffer.get());
 		surface_clear_pass->set_clear_color({0.0f, 0.0f, 0.0f, 1.0f});
 		surface_clear_pass->set_clear_depth(0.0f);
@@ -754,7 +751,6 @@ void game::setup_rendering()
 		surface_outline_pass->set_outline_color(math::fvec4{1.0f, 1.0f, 1.0f, 1.0f});
 		
 		surface_compositor = std::make_unique<render::compositor>();
-		surface_compositor->add_pass(surface_cascaded_shadow_map_pass.get());
 		surface_compositor->add_pass(surface_clear_pass.get());
 		surface_compositor->add_pass(sky_pass.get());
 		surface_compositor->add_pass(surface_material_pass.get());
diff --git a/src/game/game.hpp b/src/game/game.hpp
index 3bebb97..b0339cc 100644
--- a/src/game/game.hpp
+++ b/src/game/game.hpp
@@ -90,7 +90,6 @@ namespace render
 	class material_pass;
 	class renderer;
 	class outline_pass;
-	class cascaded_shadow_map_pass;
 	class simple_render_pass;
 	class sky_pass;
 }
@@ -333,7 +332,6 @@ public:
 	std::unique_ptr<render::clear_pass> underground_clear_pass;
 	std::unique_ptr<render::material_pass> underground_material_pass;
 	std::unique_ptr<render::compositor> underground_compositor;
-	std::unique_ptr<render::cascaded_shadow_map_pass> surface_cascaded_shadow_map_pass;
 	std::unique_ptr<render::clear_pass> surface_clear_pass;
 	std::unique_ptr<render::sky_pass> sky_pass;
 	std::unique_ptr<render::material_pass> surface_material_pass;
diff --git a/src/game/states/experiments/treadmill-experiment-state.cpp b/src/game/states/experiments/treadmill-experiment-state.cpp
index d41c211..7982675 100644
--- a/src/game/states/experiments/treadmill-experiment-state.cpp
+++ b/src/game/states/experiments/treadmill-experiment-state.cpp
@@ -117,10 +117,10 @@ treadmill_experiment_state::treadmill_experiment_state(::game& ctx):
 	// Create nest exterior
 	{
 		scene_component nest_exterior_scene_component;
-		nest_exterior_scene_component.object = std::make_shared<scene::static_mesh>(ctx.resource_manager->load<render::model>("cube-nest-200mm-exterior.mdl"));
+		nest_exterior_scene_component.object = std::make_shared<scene::static_mesh>(ctx.resource_manager->load<render::model>("cube-nest-200mm-interior.mdl"));
 		nest_exterior_scene_component.layer_mask = 1;
 		
-		auto nest_exterior_mesh = ctx.resource_manager->load<geom::brep_mesh>("cube-nest-200mm-exterior.msh");
+		auto nest_exterior_mesh = ctx.resource_manager->load<geom::brep_mesh>("cube-nest-200mm-interior.msh");
 		
 		auto nest_exterior_rigid_body = std::make_unique<physics::rigid_body>();
 		nest_exterior_rigid_body->set_mass(0.0f);
@@ -349,8 +349,8 @@ void treadmill_experiment_state::create_third_person_camera_rig()
 	spring_arm.near_focal_plane_height = 8.0 * subject_scale;
 	spring_arm.far_focal_plane_height = 80.0 * subject_scale;
 	spring_arm.near_hfov = math::radians(90.0);
-	spring_arm.far_hfov = math::radians(45.0);
-	// spring_arm.far_hfov = math::radians(90.0);
+	// spring_arm.far_hfov = math::radians(45.0);
+	spring_arm.far_hfov = math::radians(90.0);
 	spring_arm.zoom = 0.25;
 	spring_arm.focal_point_offset = {0, static_cast<double>(worker_phenome->legs->standing_height) * subject_scale, 0};
 	
diff --git a/src/game/world.cpp b/src/game/world.cpp
index 32ad064..9277f74 100644
--- a/src/game/world.cpp
+++ b/src/game/world.cpp
@@ -362,7 +362,8 @@ void create_sun(::game& ctx)
 		ctx.sun_light->set_shadow_caster(true);
 		ctx.sun_light->set_shadow_framebuffer(ctx.shadow_map_framebuffer);
 		ctx.sun_light->set_shadow_bias(0.005f);
-		ctx.sun_light->set_shadow_distance(50.0f);
+		ctx.sun_light->set_shadow_max_distance(20.0f);
+		ctx.sun_light->set_shadow_fade_range(5.0f);
 		ctx.sun_light->set_shadow_cascade_count(4);
 		ctx.sun_light->set_shadow_cascade_distribution(0.8f);