feat(renderer): add selectable debug render modes

crates/renderer/src/device.rs

@@ -53,9 +53,13 @@ pub fn create_logical_device(
     let mut dynamic_rendering_features =
         vk::PhysicalDeviceDynamicRenderingFeatures::default().dynamic_rendering(true);
 
+    // `fillModeNonSolid` unlocks the `POINT` and `LINE` polygon modes used by the debug render modes.
+    let enabled_features = vk::PhysicalDeviceFeatures::default().fill_mode_non_solid(true);
+
     let create_info = vk::DeviceCreateInfo::default()
         .queue_create_infos(std::slice::from_ref(&queue_info))
         .enabled_extension_names(&device_extensions)
+        .enabled_features(&enabled_features)
         .push_next(&mut synchronization2_features)
         .push_next(&mut dynamic_rendering_features);
 

crates/renderer/src/lib.rs

@@ -28,7 +28,7 @@ use raw_window_handle::{RawDisplayHandle, RawWindowHandle};
 use std::ffi::c_char;
 
 pub use error::RendererError;
-pub use renderer::{MeshKey, Renderer};
+pub use renderer::{MeshKey, RenderMode, Renderer};
 
 use std::collections::HashMap;
 
@@ -124,8 +124,17 @@ impl Renderer {
 
         // 12. Graphics Pipeline Configuration
         let pipeline_layout = pipeline::create_pipeline_layout(&device)?;
-        let graphics_pipeline =
+
-            pipeline::create_graphics_pipeline(&device, pipeline_layout, swapchain_format)?;
+        // One pipeline per render mode, built up front so switching modes is a bind-time choice rather than a pipeline compilation stall. All variants share `pipeline_layout`; only their rasterisation state differs.
+        let mut pipelines = [vk::Pipeline::null(); RenderMode::COUNT];
+        for mode in RenderMode::ALL {
+            pipelines[mode.index()] = pipeline::create_graphics_pipeline(
+                &device,
+                pipeline_layout,
+                swapchain_format,
+                mode.polygon_mode(),
+            )?;
+        }
 
         let (depth_image, depth_allocation, depth_image_view) =
             create_depth_resources(&device, &mut allocator, swapchain_extent)?;
@@ -155,7 +164,8 @@ impl Renderer {
             depth_allocation: Some(depth_allocation),
             depth_image_view,
             pipeline_layout,
-            graphics_pipeline,
+            pipelines,
+            render_mode: RenderMode::default(),
             sync: Some(sync),
             current_frame: 0,
         })

crates/renderer/src/pipeline.rs

@@ -67,6 +67,7 @@ pub fn create_graphics_pipeline(
     device: &Device,
     layout: vk::PipelineLayout,
     color_format: vk::Format,
+    polygon_mode: vk::PolygonMode,
 ) -> Result<vk::Pipeline, RendererError> {
     // 1. Load and compile shader modules
     let (vert_module, frag_module) = load_shader_modules(device)?;
@@ -101,7 +102,7 @@ pub fn create_graphics_pipeline(
     let rasterizer = vk::PipelineRasterizationStateCreateInfo::default()
         .depth_clamp_enable(false)
         .rasterizer_discard_enable(false)
-        .polygon_mode(vk::PolygonMode::FILL)
+        .polygon_mode(polygon_mode)
         .line_width(1.0)
         .cull_mode(vk::CullModeFlags::BACK)
         .front_face(vk::FrontFace::COUNTER_CLOCKWISE)

crates/renderer/src/renderer.rs

@@ -10,6 +10,41 @@ use std::collections::HashMap;
 /// Opaque, renderer-side identifier for one uploaded chunk mesh.
 pub type MeshKey = (i32, i32, i32);
 
+/// Selects how chunk meshes are rasterised.
+///
+/// Non-[`RenderMode::Filled`] variants are debug modes for inspecting the mesher's output; they are not gameplay state. One pipeline is built per variant at initialisation and held in [`Renderer::pipelines`], indexed by [`RenderMode::index`].
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub enum RenderMode {
+    /// Filled triangles; the normal presentation path.
+    #[default]
+    Filled,
+    /// One point per polygon vertex, exposing the density of the geometry the mesher emitted.
+    Points,
+}
+
+impl RenderMode {
+    /// Number of variants, and therefore the number of pipelines built at initialisation.
+    pub const COUNT: usize = 2;
+
+    /// Every variant, in discriminant order. The array length is checked against [`RenderMode::COUNT`] at compile time, so a new variant that is not listed here fails to build.
+    pub const ALL: [Self; Self::COUNT] = [Self::Filled, Self::Points];
+
+    /// Returns the rasterisation polygon mode backing this render mode.
+    #[must_use]
+    pub const fn polygon_mode(self) -> vk::PolygonMode {
+        match self {
+            Self::Filled => vk::PolygonMode::FILL,
+            Self::Points => vk::PolygonMode::POINT,
+        }
+    }
+
+    /// Returns this mode's position in [`RenderMode::ALL`], used to index [`Renderer::pipelines`].
+    #[must_use]
+    pub const fn index(self) -> usize {
+        self as usize
+    }
+}
+
 /// GPU resources for a single chunk mesh, drawn at a fixed world offset.
 pub(crate) struct GpuMesh {
     /// Buffer holding the chunk's vertex data.
@@ -70,8 +105,10 @@ pub struct Renderer {
     pub(crate) command_buffers: Vec<vk::CommandBuffer>,
     /// The layout of the graphics pipeline.
     pub(crate) pipeline_layout: vk::PipelineLayout,
-    /// The compiled graphics pipeline state.
+    /// One compiled pipeline per [`RenderMode`], indexed by [`RenderMode::index`]. All variants share [`Renderer::pipeline_layout`] and differ only in rasterisation state.
-    pub(crate) graphics_pipeline: vk::Pipeline,
+    pub(crate) pipelines: [vk::Pipeline; RenderMode::COUNT],
+    /// The rasterisation mode selected for subsequent frames, chosen by [`Renderer::set_render_mode`].
+    pub(crate) render_mode: RenderMode,
     /// Memory manager for GPU allocations.
     pub(crate) allocator: Option<Allocator>,
     /// Uploaded chunk meshes, keyed by an opaque renderer-side handle and drawn independently.
@@ -385,10 +422,11 @@ impl Renderer {
     /// Issues the actual draw calls for the frame.
     fn issue_draw_calls(&self, cmd: vk::CommandBuffer, camera_view: glam::Mat4) {
         unsafe {
+            // The bound pipeline is the sole difference between render modes; every other command recorded below is mode-independent.
             self.device.cmd_bind_pipeline(
                 cmd,
                 vk::PipelineBindPoint::GRAPHICS,
-                self.graphics_pipeline,
+                self.pipelines[self.render_mode.index()],
             );
 
             #[expect(
@@ -592,6 +630,17 @@ impl Renderer {
         Ok(())
     }
 
+    /// Sets the rasterisation mode used for subsequent frames.
+    pub const fn set_render_mode(&mut self, mode: RenderMode) {
+        self.render_mode = mode;
+    }
+
+    /// Returns the rasterisation mode currently in use.
+    #[must_use]
+    pub const fn render_mode(&self) -> RenderMode {
+        self.render_mode
+    }
+
     /// Frees the GPU mesh stored under `key`. Does nothing if no mesh is present.
     pub fn remove_mesh(&mut self, key: MeshKey) {
         let Some(mesh) = self.chunk_meshes.remove(&key) else {
@@ -617,7 +666,10 @@ impl Drop for Renderer {
         unsafe {
             let _ = self.device.device_wait_idle();
 
-            self.device.destroy_pipeline(self.graphics_pipeline, None);
+            // Every rasterisation variant is a distinct pipeline object and must be destroyed, or the validation layers report the survivors as leaked at teardown.
+            for pipeline in self.pipelines {
+                self.device.destroy_pipeline(pipeline, None);
+            }
             self.device
                 .destroy_pipeline_layout(self.pipeline_layout, None);