drawshinylighting.dart

import 'dart:math';
import 'package:image/image.dart';
import 'pixel.dart';
import 'vector.dart';
import 'sphere.dart';
import 'postprocessor.dart';
import 'material.dart';
import 'lighting.dart';

/**
 * Draw spheres, with shiny ligthing.
 * Save it as a PNG.
 * Open it via the default Mac app.
 */

// Globals - Ugh
// ToDo - Clean this mess up
Vector3 hit, N; // point is aka hit

Vector3 reflect(Vector3 I, Vector3 N) {
  return I - N.timesDouble(2.0) * (I * N);
}

void main() {
  const filename = "shinylighting.png";
  const width = 1024;
  const height = 768;
  const FOV = pi / 2.0;

  List<Pixel> pixels = List<Pixel>(width * height);
  Image im = Image(width, height);

  // Image is prepped - draw!
  Material ivory =
      Material(Vector2(0.6, 0.3), Pixel(0.4, 0.4, 0.3), 50);
  Material red_rubber =
      Material(Vector2(0.9, 0.1), Pixel(0.3, 0.1, 0.1), 10);

  List<Sphere> spheres = List<Sphere>();
  spheres.add(Sphere(Vector3(-1, -1.5, -12), 2.0, red_rubber));
  spheres.add(Sphere(Vector3(1.5, -0.5, -18), 3.0, red_rubber));
  spheres.add(Sphere(Vector3(7, 5, -18), 4.0, ivory));
  spheres.add(Sphere(Vector3(-3, 0, -16), 2.0, ivory));

  List<Lighting> lights = List<Lighting>();
  lights.add(Lighting(Vector3(30, 50, -25), 1.8));
  lights.add(Lighting(Vector3(-20, 20, 20), 1.5));
  lights.add(Lighting(Vector3(30, 20, 30), 1.7));

  // Ray casting is triggered from here
  for (var x = 0; x < width; x++) {
    for (var y = 0; y < height; y++) {
      double xp = (2 * (x + 0.5) / width - 1) * tan(FOV / 2.0) * width / height;
      double yp = -(2 * (y + 0.5) / height - 1) * tan(FOV / 2.0);
      Vector3 direction = Vector3(xp, yp, -1);
      direction.normalise();
      pixels[x + (y * width)] =
          castRay(Vector3(0, 0, 0), direction, spheres, lights);
    }
  }

  PostProcessor.performPostProcesses(im, pixels, filename);
}

bool sceneIntersect(Vector3 origin, Vector3 direction, List<Sphere> spheres,
    Material material) {
  double spheresDistance = double.maxFinite;

  for (var i = 0; i < spheres.length; i++) {
    double dist_i = 10.0;

    if (spheres[i].rayIntersect(origin, direction, dist_i) &&
        (dist_i < spheresDistance)) {
      spheresDistance = dist_i;
      hit = origin + direction.timesDouble(dist_i);
      N = (hit - spheres[i].center).normalise();
      material.setDiffuseColour(spheres[i].material.diffuseColour);
    }
  }

  return spheresDistance < 1000;
}

Pixel castRay(Vector3 origin, Vector3 direction, List<Sphere> spheres,
    List<Lighting> lights) {
  Material material = Material(Vector2(0.5, 0.3), Pixel(0, 0, 128), 30.0);
  if (!sceneIntersect(origin, direction, spheres, material)) {
    return Pixel(0.2, 0.7, 0.8);
  }
  double diffuse_light_intensity = 0.0, specular_light_intensity = 0.0;

  for (var i = 0; i < lights.length; i++) {
    Vector3 lightdir = (lights[i].position - hit).normalise();
    diffuse_light_intensity += lights[i].intensity * max(0.0, lightdir & N);
    Vector3 ref = reflect(lightdir.timesDouble(-1.0), N).timesDouble(-1);
    specular_light_intensity = pow(max(0.0, direction & ref), material.specularExponent)*lights[i].intensity;
  }

  return material.timesDouble(diffuse_light_intensity * material.albedo.x) +
      Pixel(1.0, 1.0, 1.0).timesDouble(specular_light_intensity * material.albedo.y);
}