camera: protoype supersampling for rayon render pass.

rtchallenge/Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "addr2line"
 version = "0.15.2"
@@ -306,6 +308,17 @@ dependencies = [
  "backtrace",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcd999463524c52659517fe2cea98493cfe485d10565e7b0fb07dbba7ad2753"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "gimli"
 version = "0.24.0"
@@ -508,6 +521,12 @@ dependencies = [
  "miniz_oxide 0.3.7",
 ]
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857"
+
 [[package]]
 name = "proc-macro-error"
 version = "1.0.4"
@@ -550,6 +569,46 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rand"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e7573632e6454cf6b99d7aac4ccca54be06da05aca2ef7423d22d27d4d4bcd8"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+ "rand_hc",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d34f1408f55294453790c48b2f1ebbb1c5b4b7563eb1f418bcfcfdbb06ebb4e7"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d51e9f596de227fda2ea6c84607f5558e196eeaf43c986b724ba4fb8fdf497e7"
+dependencies = [
+ "rand_core",
+]
+
 [[package]]
 name = "rayon"
 version = "1.5.1"
@@ -606,6 +665,7 @@ dependencies = [
  "enum-utils",
  "num_cpus",
  "png",
+ "rand",
  "rayon",
  "serde",
  "serde_json",
@@ -828,6 +888,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.10.2+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.74"

rtchallenge/Cargo.toml

@@ -16,6 +16,7 @@ criterion = "0.3.4"
 enum-utils = "0.1.2"
 num_cpus = "1.13.0"
 png = "0.16.8"
+rand = "0.8.4"
 rayon = "1.5.1"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0.64"

rtchallenge/src/camera.rs

@@ -7,6 +7,7 @@ use std::{
     thread,
 };
 
+use rand::Rng;
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use serde::Deserialize;
 use structopt::StructOpt;
@@ -114,6 +115,31 @@ impl Camera {
     pub fn pixel_size(&self) -> f32 {
         self.pixel_size
     }
+    pub fn supersample_rays_for_pixel(&self, px: usize, py: usize, samples: usize) -> Vec<Ray> {
+        let mut rng = rand::thread_rng();
+
+        (0..samples)
+            .map(|_| {
+                // The offset from the edge of the canvas to the pixel's corner.
+                let xoffset = (px as f32 + rng.gen::<f32>()) * self.pixel_size;
+                let yoffset = (py as f32 + rng.gen::<f32>()) * self.pixel_size;
+
+                // The untransformed coordinates of the pixle in world space.
+                // (Remember that the camera looks toward -z, so +x is to the left.)
+                let world_x = self.half_width - xoffset;
+                let world_y = self.half_height - yoffset;
+
+                // Using the camera matrix, transofmrm the canvas point and the origin,
+                // and then compute the ray's direction vector.
+                // (Remember that the canvas is at z>=-1).
+                let pixel = self.inverse_transform * Tuple::point(world_x, world_y, -1.);
+                let origin = self.inverse_transform * Tuple::point(0., 0., 0.);
+                let direction = (pixel - origin).normalize();
+
+                Ray::new(origin, direction)
+            })
+            .collect()
+    }
 
     /// Calculate ray that starts at the camera and passes through the (x,y)
     /// pixel on the canvas.
@@ -297,9 +323,19 @@ impl Camera {
         (0..self.vsize).into_par_iter().for_each(|y| {
             let mut row_image = Canvas::new(self.hsize, 1, BLACK);
             for x in 0..self.hsize {
-                let ray = self.ray_for_pixel(x, y);
+                const SAMPLES: usize = 0;
-                let color = w.color_at(&ray);
+                if SAMPLES > 0 {
-                row_image.set(x, 0, color);
+                    let color = self
+                        .supersample_rays_for_pixel(x, y, SAMPLES)
+                        .iter()
+                        .map(|ray| w.color_at(&ray))
+                        .fold(BLACK, |acc, c| acc + c);
+                    row_image.set(x, 0, color / SAMPLES as f32);
+                } else {
+                    let ray = self.ray_for_pixel(x, y);
+                    let color = w.color_at(&ray);
+                    row_image.set(x, 0, color);
+                }
             }
             // TODO(wathiede): create a row based setter for memcpying the row as a whole.
             let mut image = image_mu.lock().expect("failed to lock image mutex");