Add a stats display for scene complexity (#322)

examples/with_winit/README.md

@@ -20,5 +20,6 @@ $ cargo run -p with_winit --release -- [SVG FILES]
 - Space resets the position and zoom of the image.
 - S toggles the frame statistics layer
 - C resets the min/max frame time tracked by statistics
+- D toggles displaying the required number of each kind of dynamically allocated element (default: off)
 - V toggles VSync on/off (default: on)
 - Escape exits the program.

examples/with_winit/src/lib.rs

@@ -27,7 +27,7 @@ use vello::{
     util::RenderContext,
     Renderer, Scene, SceneBuilder,
 };
-use vello::{RendererOptions, SceneFragment};
+use vello::{BumpAllocators, RendererOptions, SceneFragment};
 
 use winit::{
     event_loop::{EventLoop, EventLoopBuilder},
@@ -100,6 +100,8 @@ fn run(
     let mut images = ImageCache::new();
     let mut stats = stats::Stats::new();
     let mut stats_shown = true;
+    let mut scene_complexity: Option<BumpAllocators> = None;
+    let mut complexity_shown = false;
     let mut vsync_on = true;
     let mut frame_start_time = Instant::now();
     let start = Instant::now();
@@ -150,6 +152,9 @@ fn run(
                             Some(VirtualKeyCode::S) => {
                                 stats_shown = !stats_shown;
                             }
+                            Some(VirtualKeyCode::D) => {
+                                complexity_shown = !complexity_shown;
+                            }
                             Some(VirtualKeyCode::C) => {
                                 stats.clear_min_and_max();
                             }
@@ -326,6 +331,7 @@ fn run(
                     width as f64,
                     height as f64,
                     stats.samples(),
+                    complexity_shown.then_some(scene_complexity).flatten(),
                     vsync_on,
                 );
             }
@@ -336,7 +342,7 @@ fn run(
                 .expect("failed to get surface texture");
             #[cfg(not(target_arch = "wasm32"))]
             {
-                vello::block_on_wgpu(
+                scene_complexity = vello::block_on_wgpu(
                     &device_handle.device,
                     renderers[render_state.surface.dev_id]
                         .as_mut()

examples/with_winit/src/stats.rs

@@ -19,7 +19,7 @@ use std::collections::VecDeque;
 use vello::{
     kurbo::{Affine, PathEl, Rect},
     peniko::{Brush, Color, Fill, Stroke},
-    SceneBuilder,
+    BumpAllocators, SceneBuilder,
 };
 
 const SLIDING_WINDOW_SIZE: usize = 100;
@@ -40,6 +40,7 @@ impl Snapshot {
         viewport_width: f64,
         viewport_height: f64,
         samples: T,
+        bump: Option<BumpAllocators>,
         vsync: bool,
     ) where
         T: Iterator<Item = &'a u64>,
@@ -59,13 +60,23 @@ impl Snapshot {
             &Rect::new(0., 0., width, height),
         );
 
-        let labels = [
+        let mut labels = vec![
             format!("Frame Time: {:.2} ms", self.frame_time_ms),
             format!("Frame Time (min): {:.2} ms", self.frame_time_min_ms),
             format!("Frame Time (max): {:.2} ms", self.frame_time_max_ms),
             format!("VSync: {}", if vsync { "on" } else { "off" }),
             format!("Resolution: {viewport_width}x{viewport_height}"),
         ];
+        if let Some(bump) = &bump {
+            if bump.failed >= 1 {
+                labels.push(format!("Allocation Failed!"));
+            }
+            labels.push(format!("binning: {}", bump.binning));
+            labels.push(format!("ptcl: {}", bump.ptcl));
+            labels.push(format!("tile: {}", bump.tile));
+            labels.push(format!("segments: {}", bump.segments));
+            labels.push(format!("blend: {}", bump.blend));
+        }
 
         // height / 2 is dedicated to the text labels and the rest is filled by the bar graph.
         let text_height = height * 0.5 / (1 + labels.len()) as f64;

src/lib.rs

@@ -37,6 +37,8 @@ pub use util::block_on_wgpu;
 use engine::{Engine, ExternalResource, Recording};
 use shaders::FullShaders;
 
+/// Temporary export, used in with_winit for stats
+pub use vello_encoding::BumpAllocators;
 use wgpu::{Device, Queue, SurfaceTexture, TextureFormat, TextureView};
 
 /// Catch-all error type.
@@ -196,6 +198,12 @@ impl Renderer {
     /// The texture is assumed to be of the specified dimensions and have been created with
     /// the [wgpu::TextureFormat::Rgba8Unorm] format and the [wgpu::TextureUsages::STORAGE_BINDING]
     /// flag set.
+    ///
+    /// The return value is the value of the `BumpAllocators` in this rendering, which is currently used
+    /// for debug output.
+    ///
+    /// This return type is not stable, and will likely be changed when a more principled way to access
+    /// relevant statistics is implemented
     pub async fn render_to_texture_async(
         &mut self,
         device: &Device,
@@ -203,13 +211,15 @@ impl Renderer {
         scene: &Scene,
         texture: &TextureView,
         params: &RenderParams,
-    ) -> Result<()> {
+    ) -> Result<Option<BumpAllocators>> {
         let mut render = Render::new();
         let encoding = scene.data();
         let recording = render.render_encoding_coarse(encoding, &self.shaders, params, true);
         let target = render.out_image();
         let bump_buf = render.bump_buf();
         self.engine.run_recording(device, queue, &recording, &[])?;
+
+        let mut bump: Option<BumpAllocators> = None;
         if let Some(bump_buf) = self.engine.get_download(bump_buf) {
             let buf_slice = bump_buf.slice(..);
             let (sender, receiver) = futures_intrusive::channel::shared::oneshot_channel();
@@ -219,8 +229,8 @@ impl Renderer {
             } else {
                 return Err("channel was closed".into());
             }
-            let _mapped = buf_slice.get_mapped_range();
-            // println!("{:?}", bytemuck::cast_slice::<_, u32>(&mapped));
+            let mapped = buf_slice.get_mapped_range();
+            bump = Some(bytemuck::pod_read_unaligned(&*mapped));
         }
         // TODO: apply logic to determine whether we need to rerun coarse, and also
         // allocate the blend stack as needed.
@@ -231,7 +241,7 @@ impl Renderer {
         let external_resources = [ExternalResource::Image(target, texture)];
         self.engine
             .run_recording(device, queue, &recording, &external_resources)?;
-        Ok(())
+        Ok(bump)
     }
 
     /// See [Self::render_to_surface]
@@ -242,7 +252,7 @@ impl Renderer {
         scene: &Scene,
         surface: &SurfaceTexture,
         params: &RenderParams,
-    ) -> Result<()> {
+    ) -> Result<Option<BumpAllocators>> {
         let width = params.width;
         let height = params.height;
         let mut target = self
@@ -254,7 +264,8 @@ impl Renderer {
         if target.width != width || target.height != height {
             target = TargetTexture::new(device, width, height);
         }
-        self.render_to_texture_async(device, queue, scene, &target.view, params)
+        let bump = self
+            .render_to_texture_async(device, queue, scene, &target.view, params)
             .await?;
         let blit = self
             .blit
@@ -292,7 +303,7 @@ impl Renderer {
         }
         queue.submit(Some(encoder.finish()));
         self.target = Some(target);
-        Ok(())
+        Ok(bump)
     }
 }