Anti aliasing by multisampling

Cargo.toml

@@ -11,3 +11,4 @@ clap = { version = "4.4.8", features = ["derive"] }
 cgmath = "0.18.0"
 rayon = "1.8.0"
 image = "0.24.7"
+rand = "0.8.5"

src/main.rs

@@ -1,3 +1,5 @@
+#![feature(array_zip)]
+
 mod renderer;
 mod geometry;
 mod ray;
@@ -25,6 +27,9 @@ pub struct Args {
     /// image height
     #[arg(long)]
     height: usize,
+    /// rays per pixel
+    #[arg(long)]
+    multiplier: usize,
 }
 
 fn main() {

src/ray.rs

@@ -1,52 +1,36 @@
-use std::ops::Mul;
-use cgmath::{Angle, InnerSpace, Matrix3, Matrix4, Point3, SquareMatrix, Vector3, Vector4};
-use easy_gltf::{Camera, Projection};
+use cgmath::{InnerSpace, Matrix4, Vector3, Vector4};
+use rand::{Rng};
 
 pub struct Ray {
     pub(crate) source: Vector3<f32>,
     pub(crate) direction: Vector3<f32>,
 }
 
-pub fn construct_primary_rays(camera: &Camera,
-                              (width, height): (usize, usize),
+pub fn construct_primary_rays((width, height): (usize, usize),
                               (pixel_x_coord, pixel_y_coord): (usize, usize),
+                              cam_to_world_matrix: &Matrix4<f32>,
+                              focal_length: f32,
+                              rays_per_pixel: usize,
 ) -> Vec<Ray> {
-    //only allow perspective rendering
-    //TODO: ignoring aspect ratio here
-    let (fovy, aspect_ratio) = match camera.projection {
-        Projection::Perspective { yfov, aspect_ratio } => {
-            (yfov, aspect_ratio)
-        }
-        Projection::Orthographic { .. } => { panic!("Orthographic rendering not supported.") }
-    };
 
-    //ray origin in world space
-    let origin_world_space = camera.position();
+    let mut rays: Vec<Ray> = Vec::with_capacity(rays_per_pixel);
 
-    //use a custom transform matrix because the one from easy_gltf is fucked
-    let transform_matrix = Matrix4::from_cols(
-        camera.right().extend(0.0),
-        -camera.up().extend(0.0),
-        -camera.forward().extend(0.0),
-        origin_world_space.extend(1.0),
-    );
-
-    // the distance from the camera origin to the view plane
-    let z: f32 = height as f32 / (2.0 * fovy.mul(0.5).tan());
-
-    //TODO: take ray multiplier per pixel into account here
-    let mut rays: Vec<Ray> = Vec::with_capacity(height * width);
+    let mut rng = rand::thread_rng();
 
     //generate all rays for this pixel and add them to the rays vector
     //TODO: use blue noise here to generate multiple rays per pixel
-    rays.push(generate_single_primary_ray(
-        width,
-        height,
-        &transform_matrix,
-        z,
-        pixel_x_coord,
-        pixel_y_coord,
-        origin_world_space));
+    for _ in 0..rays_per_pixel {
+        rays.push(generate_single_primary_ray(
+            width,
+            height,
+            cam_to_world_matrix,
+            focal_length,
+            pixel_x_coord,
+            pixel_y_coord,
+            rng.gen(),
+            rng.gen()
+        ));
+    }
 
     rays
 }
@@ -57,15 +41,20 @@ fn generate_single_primary_ray(image_width: usize,
                                focal_length: f32,
                                u: usize,
                                v: usize,
-                               ray_origin: Vector3<f32>) -> Ray {
+                               u_offset: f32,
+                               v_offset: f32) -> Ray {
     //calculate the ray direction and translate it to world space
-    let direction_view_space: Vector4<f32> =
-        Vector4::new(u as f32 - (image_width as f32 / 2.0),
-                     v as f32 - (image_height as f32 / 2.0),
+    let direction_camera_space: Vector4<f32> =
+        Vector4::new(u as f32 - (image_width as f32 / 2.0) + u_offset,
+                     v as f32 - (image_height as f32 / 2.0) + v_offset,
                      focal_length,
                      0.0);
 
-    let direction_world_space = cam_to_world_transform * direction_view_space.normalize();
+    let direction_world_space =
+        cam_to_world_transform * direction_camera_space.normalize();
 
-    Ray { source: ray_origin, direction: direction_world_space.truncate().normalize() }
+    Ray {
+        source: cam_to_world_transform.w.truncate(),
+        direction: direction_world_space.truncate().normalize(),
+    }
 }

src/renderer.rs

@@ -1,9 +1,9 @@
-use std::cmp::max;
+use std::ops::Mul;
 use std::sync::{Arc, Mutex};
-use cgmath::{Vector2, Vector3, Vector4, Zero};
+use cgmath::{Angle, Matrix4, Vector2, Vector3};
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use easy_gltf::model::{Mode};
-use easy_gltf::{Camera, Scene};
+use easy_gltf::{Camera, Projection, Scene};
 use image::{DynamicImage, GenericImage, Rgba};
 use crate::Args;
 use crate::geometry::{Intersectable};
@@ -15,29 +15,61 @@ pub fn render(scenes: &Vec<Scene>,
     let render_scene: &Scene = &scenes[cl_args.scene_index];
     let render_camera: &Camera = &scenes[cl_args.scene_index].cameras[cl_args.camera_index];
 
+    //use a custom transform matrix because the one from easy_gltf is fucked
+    let transform_matrix = Matrix4::from_cols(
+        render_camera.right().extend(0.0),
+        -render_camera.up().extend(0.0),
+        -render_camera.forward().extend(0.0),
+        render_camera.position().extend(1.0),
+    );
+
+    //only allow perspective rendering
+    //TODO: ignoring aspect ratio here. Maybe implement an assertion?
+    let fovy = match render_camera.projection {
+        Projection::Perspective { yfov, aspect_ratio: _aspect_ratio } => {
+            yfov
+        }
+        Projection::Orthographic { .. } => { panic!("Orthographic rendering not supported.") }
+    };
+
+
+    // the distance from the camera origin to the view plane
+    let z: f32 = cl_args.height as f32 / (2.0 * fovy.mul(0.5).tan());
+
     //iterate over all pixels in the image
     (0..cl_args.width).into_par_iter().for_each(|px| {
         (0..cl_args.height).into_par_iter().for_each(|py| {
             //construct all rays
             let rays: Vec<Ray> = construct_primary_rays(
-                render_camera,
                 (cl_args.width, cl_args.height),
                 (px, py),
+                &transform_matrix,
+                z,
+                cl_args.multiplier,
             );
 
-            //let the initial pixel color be black and transparent
-            let mut pixel_color: Rgba<u8> = Rgba::from([0, 0, 0, 255]);
+            //let the initial pixel color be black and opaque
+            let mut pixel_luminosity: [f32; 4] = [0.0, 0.0, 0.0, 255.0];
 
             //cast each ray and get the output color
-            //TODO: in the end we will want to average the colors out here
             rays.iter().for_each(|ray| {
-                pixel_color = raytrace(ray, render_scene);
+                pixel_luminosity = raytrace(ray, render_scene, 4)
+                    .zip(pixel_luminosity)
+                    .map(|(a, b)| a as f32 + b);
             });
 
+
             //save pixel to output image
             match output_image.lock() {
                 Ok(mut image) => {
-                    image.put_pixel(px as u32, py as u32, pixel_color);
+                    //save pixel
+                    image.put_pixel(
+                        px as u32,
+                        py as u32,
+                        colormap(
+                            pixel_luminosity,
+                            cl_args.multiplier),
+                    );
                 }
                 Err(_) => { panic!("Unable to obtain lock on image!") }
             }
@@ -46,13 +78,13 @@ pub fn render(scenes: &Vec<Scene>,
 }
 
 
-fn raytrace(ray: &Ray, scene: &Scene) -> Rgba<u8> {
-    let mut pixel_color: Rgba<u8> = Rgba::from([0, 0, 0, 255]);
+fn raytrace(ray: &Ray, scene: &Scene, recursion_depth: u32) -> [u8; 4] {
+    let mut pixel_color: [u8; 4] = [0, 0, 0, 255];
 
 
     let mut smallest_t: f32 = f32::MAX;
     let mut clostest_intersection_point: Option<Vector3<f32>> = None;
-    let mut color_at_isec = [0, 0, 0, 0];
+    let mut color_at_isec: [u8; 4] = [0, 0, 0, 255];
 
     //test intersection with all models in the scene
     //TODO: Improve, to avoid iterating all models
@@ -81,7 +113,12 @@ fn raytrace(ray: &Ray, scene: &Scene) -> Rgba<u8> {
                             Vector2::new(0.0, 0.0)
                         ).map(|comp| comp * 255.0);
 
-                        color_at_isec = [color_vec[0] as u8, color_vec[1] as u8, color_vec[2] as u8, color_vec[3] as u8]
+                        color_at_isec = [
+                            color_vec[0] as u8,
+                            color_vec[1] as u8,
+                            color_vec[2] as u8,
+                            color_vec[3] as u8
+                        ]
                     }
                 }
             };
@@ -91,10 +128,28 @@ fn raytrace(ray: &Ray, scene: &Scene) -> Rgba<u8> {
     //make pixel opaque if intersection is found
     match clostest_intersection_point {
         Some(_) => {
-            pixel_color = Rgba::from(color_at_isec);
+            pixel_color = color_at_isec;
         }
         None {} => {}
     }
 
     pixel_color
 }
+
+fn colormap(luminosity_array: [f32; 4], rays_per_pixel: usize) -> Rgba<u8> {
+    luminosity_array.map(|component|
+        f32::ceil(component / rays_per_pixel as f32) as u8
+    );
+
+    //linearly map luminosity values to [0..255]
+    let range: f32 =
+        luminosity_array.iter().fold(f32::NEG_INFINITY, |a, b| a.max(*b)) -
+            luminosity_array.iter().fold(f32::INFINITY, |a, b| a.min(*b));
+
+    let color_value: [u8; 4] =
+        luminosity_array.map(|lum_val|
+            f32::ceil((lum_val / range) * 255.0) as u8
+        );
+
+    Rgba::from(color_value)
+}