stylized 1-bit rendering

CLAUDE.md

@@ -6,6 +6,8 @@ This file provides guidance to Claude Code when working with code in this reposi
 
 This is a pure Rust game project using SDL3 for windowing/input, wgpu for rendering, rapier3d for physics, and a low-res retro aesthetic with dithering. This is a migration from the Godot-based snow_trail project, implementing the same snow deformation system and character controller without engine dependencies.
 
+**Content Creation:** Blender 5.0 is used for terrain modeling and asset export (glTF meshes + EXR heightmaps).
+
 ## Code Style
 
 **Code Documentation Guidelines**:
@@ -143,12 +145,17 @@ SDL Events → InputState → player_input_system() → InputComponent → movem
 - Final blit pass upscales framebuffer to window using nearest-neighbor sampling
 - Depth buffer for 3D rendering with proper occlusion
 
-**Terrain Height Deformation:**
+**Terrain Rendering:**
+- glTF mesh exported from Blender 5.0 with baked height values in vertices
+- No runtime displacement in shader - vertices rendered directly
+- Separate terrain pipeline for terrain-specific rendering
+- Terrain mesh has heights pre-baked during export for optimal performance
+
+**Terrain Physics:**
 - EXR heightmap files loaded via `exr` crate (single-channel R32Float format)
-- Height displacement applied in vertex shader
-- Separate terrain pipeline with texture sampling in vertex stage
-- TerrainUniforms includes height_scale parameter for tweaking displacement strength
-- R32Float textures require non-filterable samplers (FilterMode::Nearest)
+- Heightmap loaded directly into rapier3d heightfield collider
+- No runtime sampling or computation - instant loading
+- Both glTF and EXR exported from same Blender terrain, guaranteed to match
 
 **Lighting Model:**
 - Directional light (like Godot's DirectionalLight3D)
@@ -194,7 +201,7 @@ cargo fmt
 
 WGSL shaders are stored in the `shaders/` directory:
 - `shaders/standard.wgsl` - Standard mesh rendering with directional lighting
-- `shaders/terrain.wgsl` - Terrain rendering with height displacement
+- `shaders/terrain.wgsl` - Terrain rendering with shadow mapping (no displacement)
 - `shaders/blit.wgsl` - Fullscreen blit for upscaling low-res framebuffer
 
 Shaders are loaded at runtime via `std::fs::read_to_string()`, allowing hot-reloading by restarting the application.
@@ -224,10 +231,9 @@ Shaders are loaded at runtime via `std::fs::read_to_string()`, allowing hot-relo
 **Rendering:**
 - `render.rs` - wgpu renderer, pipelines, bind groups, DrawCall execution
 - `shader.rs` - Standard mesh shader (WGSL) with diffuse+ambient lighting
-- `terrain.rs` - Terrain mesh generation and pipeline creation
+- `terrain.rs` - Terrain entity spawning, glTF loading, EXR heightmap → physics collider
 - `postprocess.rs` - Low-res framebuffer and blit shader for upscaling
 - `mesh.rs` - Vertex/Mesh structs, plane/cube mesh generation, glTF loading
-- `heightmap.rs` - EXR heightmap loading using `exr` crate
 - `draw.rs` - DrawManager (legacy, kept for compatibility)
 
 **Game Logic:**
@@ -260,32 +266,32 @@ Shaders are loaded at runtime via `std::fs::read_to_string()`, allowing hot-relo
 - **bytemuck**: Safe byte casting for GPU buffer uploads (Pod/Zeroable for vertex data)
 - **anyhow**: Ergonomic error handling
 - **gltf**: Loading 3D models in glTF format
-- **exr**: Loading EXR heightmap files (single-channel float data)
-- **image**: Image loading and processing (includes EXR support)
-- **half**: Float16 support (dependency of exr)
+- **exr**: Loading EXR heightmap files (single-channel float data for physics colliders)
 - **kurbo**: Bezier curve evaluation for movement acceleration curves
 
 ## Technical Notes
 
-### EXR Heightmap Loading
-When loading EXR files with the `exr` crate:
+### EXR Heightmap Loading (Physics Only)
+When loading EXR files with the `exr` crate for physics colliders:
 - Must import traits: `use exr::prelude::{ReadChannels, ReadLayers};`
 - Use builder pattern: `.no_deep_data().largest_resolution_level().all_channels().all_layers().all_attributes().from_file(path)`
 - Extract float data: `channel.sample_data.values_as_f32().collect()`
-- Create R32Float texture for height data
-- R32Float is non-filterable, requires `FilterMode::Nearest` sampler
+- Convert to nalgebra DMatrix for rapier3d heightfield collider
+- No GPU texture creation - physics data only
 
-### wgpu Texture Formats
-- R32Float = single-channel 32-bit float, **non-filterable**
-- Use `TextureSampleType::Float { filterable: false }` in bind group layout
-- Use `SamplerBindingType::NonFiltering` for sampler binding
-- Attempting linear filtering on R32Float causes validation errors
+### Blender Export Workflow
+**Using Blender 5.0** for terrain creation and export:
+- Export terrain as **glTF** with baked height values in mesh vertices
+- Export same terrain as **EXR** heightmap (single-channel R32Float)
+- Both files represent the same terrain data, guaranteeing visual/physics sync
+- glTF used for rendering (vertices rendered directly, no shader displacement)
+- EXR used for physics (loaded into rapier3d heightfield collider)
 
 ### Multiple Render Pipelines
 - `Pipeline` enum determines which pipeline to use per DrawCall
 - Different pipelines can have different shaders, bind group layouts, uniforms
-- Terrain pipeline: includes height texture binding in vertex stage
-- Standard pipeline: basic mesh rendering without height displacement
+- Terrain pipeline: shadow-mapped rendering with line hatching shading
+- Standard pipeline: basic mesh rendering with diffuse lighting
 - Each pipeline writes to its own uniform buffer before rendering
 
 ### ECS Component Storages
@@ -589,7 +595,8 @@ let time = Time::get_time_elapsed(); // Anywhere in code
 - ✅ Low-res framebuffer (160×120) with Bayer dithering
 - ✅ Multiple render pipelines (standard mesh + terrain)
 - ✅ Directional lighting with diffuse + ambient
-- ✅ EXR heightmap loading and terrain displacement
+- ✅ Terrain rendering (glTF with baked heights, no shader displacement)
+- ✅ EXR heightmap loading for physics colliders
 - ✅ glTF mesh loading
 - ✅ render_system (ECS-based DrawCall generation)