// shader
private static Vector Shade(Ray ray, int n)
{
var record = new HitRecord();
if (World.Hit(ray, 0.01f, float.MaxValue, ref record))
{
var scattered = new Ray();
var attenuation = new Vector();
if (n > 0 && record.Material.Scatter(ray, record, ref attenuation, ref scattered))
{
return(Shade(scattered, n - 1).Scale(attenuation));
}
return(Vector.Zero);
}
var u = ray.Direction.Normalize();
var t = 0.5f * (u.Y + 1);
return(new Vector(1, 1, 1) * (1f - t) + new Vector(0.5f, 0.7f, 1.0f) * t);
}
private static Vec3 Color(Ray r, Hitable world, int depth)
{
HitRecord rec = new HitRecord();
if (world.Hit(r, 0.001, double.MaxValue, out rec))
{
Ray scattered = new Ray();
Vec3 attenuation = new Vec3();
Vec3 emitted = rec.Material.emitted(rec.U, rec.V, rec.P);
if (depth < 50 && rec.Material.Scatter(r, rec, out attenuation, out scattered))
{
return(emitted + attenuation * Color(scattered, world, depth + 1));
}
else
{
return(emitted);
}
}
else
{
return(new Vec3(0.0, 0.0, 0.0));
}
}
static void Main(string[] args)
{
var width = 200;
var height = 100;
var samples = 100;
var camera = new Camera();
var rand = new Random();
var world = new HitableList();
world.Add(new Sphere(
new Vector3(0, 0, -1),
0.5f
));
world.Add(new Sphere(
new Vector3(0, -100.5f, -1),
100f
));
using (var image = new Image <Rgba32>(width, height))
{
for (int j = height - 1; j >= 0; j--)
{
for (int i = 0; i < width; i++)
{
var col = new Vector3(0);
for (int s = 0; s < samples; s++)
{
// the horizontal distance from the origin as a float between 0 and 1
// with a random number between 0 and 1 added to it for each sample
var u = (i + (float)rand.NextDouble()) / (float)width;
// the vertical distance from the origin as a float between 0 and 1
// with a random number between 0 and 1 added to it for each sample
var v = 1 - ((j + (float)rand.NextDouble()) / (float)height);
var r = camera.GetRay(u, v);
col += Color(r, world);
}
// generates the average color over all the samples
col /= (float)samples;
// gamma correction
// basically fixes the color
// this is gamma 2 so you raise the color to the power 1/gamma which in this case means sqrt
col = new Vector3((float)Math.Sqrt(col.X), (float)Math.Sqrt(col.Y), (float)Math.Sqrt(col.Z));
image[i, j] = new Rgba32(col);
}
}
image.Save("images/gammacorr.png");
}
Vector3 Color(Ray r, Hitable world)
{
var rec = new HitRecord();
if (world.Hit(r, 0.001f, float.MaxValue, rec))
{
// generates a random point in a sphere that is tangent to the hitpoint
var target = rec.P + rec.Normal + RandomInUnitSphere();
// sends out a new ray in the direction of the target from the hitpoint
// returns when one of the subsequent rays either hits the sky or the t values become so close that they're basically zero
// the 0.5 means that 50% of the rays are absorbed into the material
return(0.5f * Color(new Ray(rec.P, target - rec.P), world));
}
else
{
// this creates the sky
var unitDirection = Vector3.Normalize(r.Direction); // makes direction vector go between -1 and 1
var t = 0.5f * (unitDirection.Y + 1.0f); // scales vector so it goes between 0 and 1
return((1 - t) * new Vector3(1f) + t * new Vector3(0.5f, 0.7f, 1.0f)); // linearly interpolates color
}
}
Vector3 RandomInUnitSphere()
{
var p = new Vector3();
do
{
// This generates a random point with XYZ between -1 and 1
p = 2 * new Vector3((float)rand.NextDouble(), (float)rand.NextDouble(), (float)rand.NextDouble()) - new Vector3(1);
} while (p.LengthSquared() >= 1f);
return(p);
}
}
public abstract bool Scatter(Ray rIn, HitRecord record, Vector3 attenuation, Ray scattered);
public abstract bool Hit(Ray r, float tMin, float tMax, HitRecord record);