algorithm to cast rays and build an image based on result

src/geometry.rs

@@ -1,10 +1,10 @@
-use cgmath::Vector3;
-use easy_gltf::Camera;
+use cgmath::{Angle, InnerSpace, Matrix4, SquareMatrix, Vector3, Vector4};
+use easy_gltf::{Camera, Projection};
 use easy_gltf::model::Triangle;
 
 pub struct Ray {
-    source: Vector3<f64>,
-    direction: Vector3<f64>,
+    source: Vector3<f32>,
+    direction: Vector3<f32>,
 }
 
 pub trait Intersectable {
@@ -18,10 +18,70 @@ pub trait Intersectable {
 impl Intersectable for Triangle {
     //perform muller trumbore intersection
     fn test_isec(&self, ray: &Ray) -> Option<Vector3<f32>> {
-        todo!()
+        //TODO: implement correct intersection here
+        if ray.direction.x > 0.5 &&
+            ray.direction.x < 0.6 &&
+            ray.direction.y > 0.1 &&
+            ray.direction.y < 0.6 {
+            return Some(Vector3::new(1.0, 1.0, 1.0));
+        }
+        return None;
     }
 }
 
-pub fn construct_rays(camera: &Camera) -> Vec<Ray> {
-    todo!()
+pub fn construct_primary_rays(camera: &Camera,
+                              (width, height): (usize, usize),
+                              (pixel_x_coord, pixel_y_coord): (usize, usize),
+) -> Vec<Ray> {
+    //only allow perspective rendering
+    //TODO: ignoring aspect ratio here
+    let fovy = match camera.projection {
+        Projection::Perspective { yfov, aspect_ratio: _aspect_ratio } => { yfov }
+        Projection::Orthographic { .. } => { panic!("Orthographic rendering not supported.") }
+    };
+
+    //ray origin in world space
+    let origin_world_space = camera.position();
+
+    //seems to be the distance from the camera origin to the view plane
+    let z: f32 = height as f32 / fovy.tan();
+
+    //obtain the inverse transformation Matrix
+    let inverse_transform = camera.transform.invert().unwrap_or_else(||
+        panic!("Non invertible transform Matrix. giving up.")
+    );
+
+    //TODO: take ray multiplier per pixel into account here
+    let mut rays: Vec<Ray> = Vec::with_capacity(height * width);
+
+    //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_ray(
+        width,
+        height,
+        &inverse_transform,
+        z,
+        pixel_x_coord,
+        pixel_y_coord,
+        origin_world_space));
+
+    rays
+}
+
+fn generate_ray(image_width: usize,
+                image_height: usize,
+                inverse_transform: &Matrix4<f32>,
+                focal_length: f32,
+                u: usize,
+                v: usize,
+                ray_origin: Vector3<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),
+                     -focal_length,
+                     0.0);
+    let direction_world_space = inverse_transform * direction_view_space;
+
+    Ray { source: ray_origin, direction: direction_world_space.normalize().truncate() }
 }

src/main.rs

@@ -2,31 +2,50 @@ mod renderer;
 mod geometry;
 
 use std::string::String;
+use std::sync::{Arc, Mutex};
 use clap::{Parser};
 use easy_gltf::Scene;
+use image::{DynamicImage};
 use crate::renderer::render;
 
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
-struct Args {
+pub struct Args {
     gltf_file_path: String,
     /// which scene to use in the gltf file
-    #[arg(short, long)]
+    #[arg(long)]
     scene_index: usize,
     /// which camera to render from
-    #[arg(short, long)]
+    #[arg(long)]
     camera_index: usize,
+    /// image width
+    #[arg(long)]
+    width: usize,
+    /// image height
+    #[arg(long)]
+    height: usize,
 }
 
 fn main() {
     //parse clargs
-    let args = Args::parse();
+    let args: Args = Args::parse();
 
     //load gltf scene
     let scenes: &Vec<Scene> = &easy_gltf::load(
         &args.gltf_file_path)
         .expect(&*format!("Failed to load glTF file {}", &args.gltf_file_path));
 
-    render(scenes, args.scene_index, args.camera_index)
+    //build an image
+    let output_image: Arc<Mutex<DynamicImage>> = Arc::new(Mutex::new(DynamicImage::new_rgba8(
+        args.width as u32, args.height as u32,
+    )));
+
+    render(scenes, &args, &output_image);
+    match output_image.lock() {
+        Ok(image) => {
+            image.save("result_image.png").expect("Unable to save image!");
+        }
+        Err(_) => { panic!("Error aquiring lock on image while saving!") }
+    };
 }
 

src/renderer.rs

@@ -1,26 +1,75 @@
+use std::sync::{Arc, Mutex};
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use easy_gltf::model::{Mode};
-use easy_gltf::Scene;
-use crate::geometry::{construct_rays, Intersectable, Ray};
+use easy_gltf::{Camera, Scene};
+use image::{DynamicImage, GenericImage, Rgba};
+use crate::Args;
+use crate::geometry::{construct_primary_rays, Intersectable, Ray};
 
 
-pub fn render(scenes: &Vec<Scene>, scene_idx: usize, camera_idx: usize) {
-    //construct all rays and cast them all
-    let rays: Vec<Ray> = construct_rays(&scenes[scene_idx].cameras[camera_idx]);
-    rays.into_par_iter().for_each(|ray| {
-        //test intersection with all models in the scene
-        //TODO: Improve, to avoid iterating all models
-        scenes[scene_idx].models.iter().for_each(|model| {
-            match model.mode() {
-                Mode::Triangles => {
-                    //in triangle mode there will always be a triangle vector
-                    let triangles = model.triangles().unwrap();
-                    triangles.iter().for_each(|triangle| {
-                        triangle.test_isec(&ray);
-                    });
+pub fn render(scenes: &Vec<Scene>,
+              cl_args: &Args,
+              output_image: &Arc<Mutex<DynamicImage>>) {
+    let render_scene: &Scene = &scenes[cl_args.scene_index];
+    let render_camera: &Camera = &scenes[cl_args.scene_index].cameras[cl_args.camera_index];
+
+    //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),
+            );
+
+            //let the initial pixel color be white and opaque
+            let mut pixel_color: Rgba<u8> = Rgba([0, 0, 0, 255]);
+
+            //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);
+            });
+
+            //save pixel to output image
+            match output_image.lock() {
+                Ok(mut image) => {
+                    image.put_pixel(px as u32, py as u32, pixel_color);
                 }
-                _ => { panic!("Unable to render model in mode {:?}", model.mode()) }
+                Err(_) => { panic!("Unable to obtain lock on image!") }
             }
         });
     });
+}
+
+
+fn raytrace(ray: &Ray, scene: &Scene) -> Rgba<u8> {
+    let mut pixel_color: Rgba<u8> = Rgba([0, 0, 0, 255]);
+
+    //test intersection with all models in the scene
+    //TODO: Improve, to avoid iterating all models
+    scene.models.iter().for_each(|model| {
+        //get all triangles in the model
+        let triangles = match model.mode() {
+            Mode::Triangles => {
+                //in triangle mode there will always be a triangle vector
+                model.triangles().unwrap()
+            }
+            _ => { panic!("Unable to render model in mode {:?}", model.mode()) }
+        };
+
+        //iterate all triangles in a model
+        triangles.iter().for_each(|triangle| {
+            match triangle.test_isec(&ray) {
+                //boilerplate implementation to set pixel to red if any intersection happened
+                None => {}
+                Some(point) => {
+                    pixel_color.0 = [255, 255, 255, 255];
+                    return
+                }
+            };
+        });
+    });
+    pixel_color
 }