Add parallel projection support

assignment-1/.gitignore

@@ -1,5 +1,6 @@
 /target
 /assignment-1
+/examples/*.png
 *.ppm
 *.zip
 *.pdf

assignment-1/Makefile

@@ -3,12 +3,17 @@
 DOCKER := docker
 ZIP := zip
 PANDOC := pandoc
+CONVERT := convert
 
 HANDIN := hw1a.michael.zhang.zip
-BINARY := assignment-1
+BINARY := ./assignment-1
 WRITEUP := writeup.pdf
 SOURCES := $(shell find -name "*.rs")
 
+EXAMPLES := $(shell find examples -name "*.txt")
+EXAMPLES_PPM := $(patsubst %.txt,%.ppm,$(EXAMPLES))
+EXAMPLES_PNG := $(patsubst %.txt,%.png,$(EXAMPLES))
+
 all: $(HANDIN)
 
 $(BINARY): $(SOURCES)
@@ -22,8 +27,14 @@ $(BINARY): $(SOURCES)
 		cargo build --release
 	mv target/release/assignment-1 $@
 
-$(HANDIN): $(BINARY) $(WRITEUP) Cargo.toml Cargo.lock README.md
-	$(ZIP) -r $@ src $^
+$(HANDIN): $(BINARY) $(WRITEUP) Cargo.toml Cargo.lock README.md $(EXAMPLES_PNG) $(EXAMPLES_PPM)
+	$(ZIP) -r $@ src examples $^
+
+examples/%.ppm: examples/%.txt
+	cargo run -- -o $@ $<
+
+examples/%.png: examples/%.ppm
+	convert $< $@
 
 writeup.pdf: writeup.md
 	$(PANDOC) -o $@ $<

assignment-1/README.md

@@ -1,11 +1,18 @@
 # Raycaster
 
+## Bundle contents
+
 Writeup is located at `/writeup.pdf`.
 
 The binary can be found at `/assignment-1`. Run `./assignment-1 --help` to see
 how to use it. The binary has been built using the Rust Docker image, which
 should have an environment similar to CSELabs. If there is trouble running the
-binary, try building form source:
+binary, try building from source, as documented below.
+
+Examples are found in the `examples` directory. The text files are the input
+sources, and the ppm files are the corresponding outputs. They have been
+generated by running this program. For convenience, pngs have also been provided
+using imagemagick.
 
 ## Building from source
 

assignment-1/examples/objects.txt

@@ -0,0 +1,21 @@
+imsize 640 480
+eye 0 0 3
+viewdir 0 0 -1
+hfov 120
+updir 0 1 0
+bkgcolor 0.1 0.1 0.1
+
+mtlcolor 0 0.5 0.5
+sphere -1 -2 -5 2
+sphere 3 -5 -1 0.5
+
+mtlcolor 0.5 0.5 1
+sphere 1 2 -3 3
+sphere -6 3 -4 1
+
+mtlcolor 0.5 0 0.5
+sphere 5 5 -1 1
+sphere -6 -4 -8 7
+
+mtlcolor 0.5 1 0.5
+cylinder 2 1 -2 1 -2 1 1 2

assignment-1/src/input_file.rs

@@ -4,7 +4,7 @@ use anyhow::Result;
 
 use crate::{
   image::Color,
-  scene_data::{Object, Scene, Sphere},
+  scene_data::{Cylinder, Object, ObjectKind, Scene, Sphere},
   vec3::Vec3,
 };
 
@@ -35,6 +35,10 @@ pub fn parse_input_file(path: impl AsRef<Path>) -> Result<Scene> {
         scene.image_width = width;
         scene.image_height = height;
       }
+    } else if keyword == "projection" {
+      if let Some("parallel") = parts.next() {
+        scene.parallel_projection = true;
+      }
     }
     // Do float parsing instead
     else {
@@ -42,11 +46,11 @@ pub fn parse_input_file(path: impl AsRef<Path>) -> Result<Scene> {
         .map(|s| s.parse::<f64>().map_err(|e| e.into()))
         .collect::<Result<Vec<_>>>()?;
 
-      let read_vec3 = || {
+      let read_vec3 = |start: usize| {
         if parts.len() < 3 {
           bail!("Vec3 requires 3 components.");
         }
-        Ok(Vec3::new(parts[0], parts[1], parts[2]))
+        Ok(Vec3::new(parts[start], parts[start + 1], parts[start + 2]))
       };
 
       let read_color = || {
@@ -57,9 +61,9 @@ pub fn parse_input_file(path: impl AsRef<Path>) -> Result<Scene> {
       };
 
       match keyword {
-        "eye" => scene.eye_pos = read_vec3()?,
-        "viewdir" => scene.view_dir = read_vec3()?,
-        "updir" => scene.up_dir = read_vec3()?,
+        "eye" => scene.eye_pos = read_vec3(0)?,
+        "viewdir" => scene.view_dir = read_vec3(0)?,
+        "updir" => scene.up_dir = read_vec3(0)?,
 
         "hfov" => scene.hfov = parts[0],
         "bkgcolor" => scene.bkg_color = read_color()?,
@@ -70,11 +74,30 @@ pub fn parse_input_file(path: impl AsRef<Path>) -> Result<Scene> {
           scene.material_colors.push(read_color()?);
         }
 
-        "sphere" => scene.objects.push(Object::Sphere(Sphere {
-          center: read_vec3()?,
-          radius: parts[3],
-          material: material_color.unwrap(),
-        })),
+        "sphere" => scene.objects.push(Object {
+          kind: ObjectKind::Sphere(Sphere {
+            center: read_vec3(0)?,
+            radius: parts[3],
+          }),
+          material: match material_color {
+            Some(v) => v,
+            None => bail!("Each sphere must be preceded by a `mtlcolor` line"),
+          },
+        }),
+
+        "cylinder" => scene.objects.push(Object {
+          kind: ObjectKind::Cylinder(Cylinder {
+            center: read_vec3(0)?,
+            direction: read_vec3(3)?,
+            radius: parts[6],
+            length: parts[7],
+          }),
+          material: match material_color {
+            Some(v) => v,
+            None => bail!("Each sphere must be preceded by a `mtlcolor` line"),
+          },
+        }),
+
         _ => bail!("Unknown keyword {keyword}"),
       }
     }

assignment-1/src/main.rs

@@ -14,14 +14,11 @@ use anyhow::Result;
 use clap::Parser;
 use ordered_float::NotNan;
 use rayon::prelude::{IntoParallelIterator, ParallelIterator};
+use scene_data::ObjectKind;
 
 use crate::image::Image;
 use crate::input_file::parse_input_file;
 use crate::ray::Ray;
-use crate::scene_data::Object;
-
-/// Viewing distance
-const ARBITRARY_D: f64 = 1.0;
 
 /// Simple raycaster.
 #[derive(Parser)]
@@ -35,6 +32,14 @@ struct Opt {
   /// with an extension of .ppm)
   #[clap(short = 'o', long = "output")]
   output_path: Option<PathBuf>,
+
+  /// Force parallel projection to be used
+  #[clap(long = "parallel")]
+  force_parallel: bool,
+
+  /// Override distance from eye
+  #[clap(long = "distance", default_value = "1.0")]
+  distance: f64,
 }
 
 fn main() -> Result<()> {
@@ -43,10 +48,15 @@ fn main() -> Result<()> {
     .output_path
     .unwrap_or_else(|| opt.input_path.with_extension("ppm"));
 
-  let scene = parse_input_file(&opt.input_path)?;
+  let mut scene = parse_input_file(&opt.input_path)?;
+  let distance = opt.distance;
+
+  if opt.force_parallel {
+    scene.parallel_projection = true;
+  }
 
   // Compute the viewing window
-  let view_window = scene.compute_viewing_window();
+  let view_window = scene.compute_viewing_window(distance);
 
   // Translate image pixels to real-world 3d coords
   let translate_pixel = {
@@ -79,34 +89,50 @@ fn main() -> Result<()> {
   let pixels = pixels_iter
     .map(|(px, py)| {
       let pixel_in_space = translate_pixel(px, py);
-      let ray = Ray::from_endpoints(scene.eye_pos, pixel_in_space);
+
+      let ray_start = if scene.parallel_projection {
+        // For a parallel projection, we'll just take the view direction and
+        // subtract it from the target point. This means every single
+        // ray will be viewed from a point at infinity, rather than a single eye
+        // position.
+        let n = scene.view_dir.unit();
+        let view_dir = n * distance;
+        pixel_in_space - view_dir
+      } else {
+        scene.eye_pos
+      };
+
+      let ray = Ray::from_endpoints(ray_start, pixel_in_space);
 
       let earliest_intersection = scene
         .objects
         .iter()
         .filter_map(|object| {
-          let sphere = match object {
-            Object::Sphere(v) => v,
-            _ => return None, /* TODO: Handle other object types for
-                               * intersection as well */
+          use ObjectKind::*;
+          let intersection_point_opt = match &object.kind {
+            Sphere(sphere) => ray.intersects_sphere_at(&sphere),
+            Cylinder(cylinder) => ray.intersects_cylinder_at(&cylinder),
           };
 
-          // Return both the t and the sphere, because we want to sort on the t
-          // but later retrieve attributes from the sphere
-          ray.intersects_at(sphere).and_then(|t| {
+          intersection_point_opt.and_then(|t| {
             // Unfortunately, IEEE floats in Rust don't have total ordering,
             // because NaNs violate ordering properties. The way to remedy this
             // is to ensure we don't have NaNs by wrapping it into this type,
             // which then implements total ordering
             let t = NotNan::new(t);
-            t.ok().map(|t| (t, sphere))
+
+            // Return both the t and the sphere, because we want to sort on the
+            // t but later retrieve attributes from the sphere
+            t.ok().map(|t| (t, object))
           })
         })
         // Sort the list of intersection times by the lowest one.
         .min_by_key(|(t, _)| *t);
 
       let pixel_color = match earliest_intersection {
-        Some((_, sphere)) => scene.material_colors[sphere.material],
+        // Take the object's material color
+        Some((_, object)) => scene.material_colors[object.material],
+
         // There was no intersection, so this should default to the scene's
         // background color
         None => scene.bkg_color,

assignment-1/src/ray.rs

@@ -1,4 +1,4 @@
-use crate::scene_data::Sphere;
+use crate::scene_data::{Cylinder, Sphere};
 use crate::vec3::Vec3;
 
 /// A normalized parametric Ray of the form (origin + direction * time)
@@ -30,7 +30,7 @@ impl Ray {
   /// sphere.
   ///
   /// If there is no intersection point, returns None.
-  pub fn intersects_at(&self, sphere: &Sphere) -> Option<f64> {
+  pub fn intersects_sphere_at(&self, sphere: &Sphere) -> Option<f64> {
     let a = self.direction.x.powi(2)
       + self.direction.y.powi(2)
       + self.direction.z.powi(2);
@@ -64,6 +64,15 @@ impl Ray {
       _ => unreachable!("Invalid determinant value: {discriminant}"),
     }
   }
+
+  /// Given a cylinder, returns the first time at which this ray intersects the
+  /// cylinder.
+  ///
+  /// If there is no intersection point, returns None.
+  pub fn intersects_cylinder_at(&self, cylinder: &Cylinder) -> Option<f64> {
+    // TODO: Implement
+    None
+  }
 }
 
 #[cfg(test)]
@@ -82,10 +91,9 @@ mod tests {
     let sphere = Sphere {
       center: Vec3::new(0.0, 0.0, -10.0),
       radius: 4.0,
-      material: 0,
     };
 
-    let point = ray.intersects_at(&sphere).map(|t| ray.eval(t));
+    let point = ray.intersects_sphere_at(&sphere).map(|t| ray.eval(t));
 
     // the intersection point in this case is (0, 0, -6)
     assert_eq!(point, Some(Vec3::new(0.0, 0.0, -6.0)));
@@ -100,10 +108,9 @@ mod tests {
     let sphere = Sphere {
       center: Vec3::new(0.0, 0.0, -10.0),
       radius: 4.0,
-      material: 0,
     };
 
     // oops! In this case, the ray does not intersect the sphere.
-    assert_eq!(ray.intersects_at(&sphere), None);
+    assert_eq!(ray.intersects_sphere_at(&sphere), None);
   }
 }

assignment-1/src/scene_data.rs

@@ -1,23 +1,31 @@
-use crate::{image::Color, vec3::Vec3, ARBITRARY_D};
+use crate::{image::Color, vec3::Vec3};
 
 #[derive(Debug)]
 pub struct Sphere {
   pub center: Vec3,
   pub radius: f64,
+}
+
+#[derive(Debug)]
+pub struct Cylinder {
+  pub center: Vec3,
+  pub direction: Vec3,
+  pub radius: f64,
+  pub length: f64,
+}
+
+#[derive(Debug)]
+pub struct Object {
+  pub kind: ObjectKind,
 
   /// Index into the scene's material color list
   pub material: usize,
 }
 
 #[derive(Debug)]
-pub enum Object {
+pub enum ObjectKind {
   Sphere(Sphere),
-  Cylinder {
-    center: Vec3,
-    direction: Vec3,
-    radius: f64,
-    length: f64,
-  },
+  Cylinder(Cylinder),
 }
 
 #[derive(Debug)]
@@ -36,6 +44,7 @@ pub struct Scene {
 
   /// Horizontal field of view (in degrees)
   pub hfov: f64,
+  pub parallel_projection: bool,
 
   pub image_width: usize,
   pub image_height: usize,
@@ -49,7 +58,7 @@ pub struct Scene {
 
 impl Scene {
   /// Determine the boundaries of the viewing window in world coordinates
-  pub fn compute_viewing_window(&self) -> Rect {
+  pub fn compute_viewing_window(&self, distance: f64) -> Rect {
     // Compute viewing directions
     let u = Vec3::cross(self.view_dir, self.up_dir).unit();
     let v = Vec3::cross(u, self.view_dir).unit();
@@ -64,7 +73,7 @@ impl Scene {
       let w_over_2d = half_hfov.tan();
 
       // To find the viewing width we must multiply by 2d now
-      w_over_2d * 2.0 * ARBITRARY_D
+      w_over_2d * 2.0 * distance
     };
 
     let aspect_ratio = self.image_width as f64 / self.image_height as f64;
@@ -74,10 +83,10 @@ impl Scene {
     let n = self.view_dir.unit();
     #[rustfmt::skip] // Otherwise this line wraps over
     let view_window = Rect {
-      upper_left: self.eye_pos + n * ARBITRARY_D - u * (viewing_width / 2.0) + v * (viewing_height / 2.0),
-      upper_right: self.eye_pos + n * ARBITRARY_D + u * (viewing_width / 2.0) + v * (viewing_height / 2.0),
-      lower_left: self.eye_pos + n * ARBITRARY_D - u * (viewing_width / 2.0) - v * (viewing_height / 2.0),
-      lower_right: self.eye_pos + n * ARBITRARY_D + u * (viewing_width / 2.0) - v * (viewing_height / 2.0),
+      upper_left: self.eye_pos + n * distance - u * (viewing_width / 2.0) + v * (viewing_height / 2.0),
+      upper_right: self.eye_pos + n * distance + u * (viewing_width / 2.0) + v * (viewing_height / 2.0),
+      lower_left: self.eye_pos + n * distance - u * (viewing_width / 2.0) - v * (viewing_height / 2.0),
+      lower_right: self.eye_pos + n * distance + u * (viewing_width / 2.0) - v * (viewing_height / 2.0),
     };
 
     view_window

assignment-1/writeup.md

@@ -71,3 +71,12 @@ location for any pixel.
 
 (Technically really we would want the middle of the pixel, so just add
 $\frac{\Delta x + \Delta y}{2}$ to the point to get that)
+
+### Cylinder Intersection Notes
+
+First, we will transform the current point into the vector space of the
+cylinder, so that the cylinder location is $(0, 0, 0)$ and the direction vector
+is normalized into $(0, 0, 1)$.
+
+Then it's a matter of determining if the $x$ and $y$ coordinates fall into the
+space constrained by the equation $x^2 + y^2 = r^2$ and if $z \le L$.

flake.nix

@@ -20,6 +20,7 @@
             zip
             unzip
             texlive.combined.scheme-full
+            imagemagick
           ]) ++ (with toolchain; [
             cargo
             rustc