private static Vec3 trace (Ray ray, Scene scene, int depth)
{
var nearest = Num.MaxValue;
Sphere obj = null;
// search the scene for nearest intersection
foreach(var o in scene.Objects)
{
var distance = Num.MaxValue;
if (Sphere.Intersect(o, ray, out distance))
{
if (distance < nearest)
{
nearest = distance;
obj = o;
}
}
}
if (obj == null) return Vec3.Zero;
var point_of_hit = ray.Org + (ray.Dir * nearest);
var normal = Sphere.Normal(obj, point_of_hit);
bool inside = false;
if (Vec3.Dot(normal, ray.Dir) > 0)
{
inside = true;
normal = -normal;
}
Vec3 color = Vec3.Zero;
var reflection_ratio = obj.Reflection;
foreach(var l in scene.Lights)
{
var light_direction = Vec3.Normalize(l.Position - point_of_hit);
Ray r;
r.Org = point_of_hit + (normal * 1e-5f);
r.Dir = light_direction;
// go through the scene check whether we're blocked from the lights
bool blocked = false;
foreach (var o in scene.Objects)
{
if (Sphere.Intersect(o, r))
{
blocked = true;
break;
}
}
if (!blocked)
{
color += l.Color
* Math.Max(0, Vec3.Dot(normal, light_direction))
* obj.Color
* (1.0f - reflection_ratio);
}
}
var rayNormDot = Vec3.Dot(ray.Dir, normal);
Num facing = Math.Max(0, -rayNormDot);
Num fresneleffect = reflection_ratio + ((1 - reflection_ratio) * (Num)Math.Pow((1 - facing), 5));
// compute reflection
if (depth < maxDepth && reflection_ratio > 0)
{
var reflection_direction = ray.Dir + (normal * 2 * rayNormDot * (-1.0f));
Ray r;
r.Org = point_of_hit + (normal * 1e-5f);
r.Dir = reflection_direction;
var reflection = trace(r, scene, depth + 1);
color += reflection * fresneleffect;
}
// compute refraction
if (depth < maxDepth && (obj.Transparency > 0))
{
var ior = 1.5f;
var CE = Vec3.Dot(ray.Dir, normal) * (-1.0f);
ior = inside ? (1.0f) / ior : ior;
var eta = (1.0f) / ior;
var GF = (ray.Dir + normal * CE) * eta;
var sin_t1_2 = 1 - (CE * CE);
var sin_t2_2 = sin_t1_2 * (eta * eta);
if (sin_t2_2 < 1)
{
var GC = normal * (Num)Math.Sqrt(1 - sin_t2_2);
var refraction_direction = GF - GC;
Ray r;
r.Org = point_of_hit - (normal * 1e-4f);
r.Dir = refraction_direction;
var refraction = trace(r, scene, depth + 1);
color += refraction * (1 - fresneleffect) * obj.Transparency;
}
}
return color;
}
public static bool Intersect(Sphere sphere, Ray ray)
{
var l = sphere.Center - ray.Org;
var a = Vec3.Dot(l, ray.Dir);
if (a < 0) // opposite direction
return false;
var b2 = Vec3.Dot(l, l) - (a * a);
var r2 = sphere.Radius * sphere.Radius;
if (b2 > r2) // perpendicular > r
return false;
return true;
}
public static bool Intersect(Sphere sphere, Ray ray, out Num distance)
{
distance = 0;
var l = sphere.Center - ray.Org;
var a = Vec3.Dot(l, ray.Dir);
if (a < 0) // opposite direction
return false;
var b2 = Vec3.Dot(l, l) - (a * a);
var r2 = sphere.Radius * sphere.Radius;
if (b2 > r2) // perpendicular > r
return false;
var c = (Num)Math.Sqrt(r2 - b2);
var near = a - c;
var far = a + c;
distance = (near < 0) ? far : near;
// near < 0 means ray starts inside
return true;
}
private static Vec3 trace(Ray ray, Scene scene, int depth)
{
var nearest = Num.MaxValue;
Sphere obj = null;
// search the scene for nearest intersection
foreach (var o in scene.Objects)
{
var distance = Num.MaxValue;
if (Sphere.Intersect(o, ray, out distance))
{
if (distance < nearest)
{
nearest = distance;
obj = o;
}
}
}
if (obj == null)
{
return(Vec3.Zero);
}
var point_of_hit = ray.Org + (ray.Dir * nearest);
var normal = Sphere.Normal(obj, point_of_hit);
bool inside = false;
if (Vec3.Dot(normal, ray.Dir) > 0)
{
inside = true;
normal = -normal;
}
Vec3 color = Vec3.Zero;
var reflection_ratio = obj.Reflection;
foreach (var l in scene.Lights)
{
var light_direction = Vec3.Normalize(l.Position - point_of_hit);
Ray r;
r.Org = point_of_hit + (normal * 1e-5f);
r.Dir = light_direction;
// go through the scene check whether we're blocked from the lights
bool blocked = false;
foreach (var o in scene.Objects)
{
if (Sphere.Intersect(o, r))
{
blocked = true;
break;
}
}
if (!blocked)
{
color += l.Color
* Math.Max(0, Vec3.Dot(normal, light_direction))
* obj.Color
* (1.0f - reflection_ratio);
}
}
var rayNormDot = Vec3.Dot(ray.Dir, normal);
Num facing = Math.Max(0, -rayNormDot);
Num fresneleffect = reflection_ratio + ((1 - reflection_ratio) * (Num)Math.Pow((1 - facing), 5));
// compute reflection
if (depth < maxDepth && reflection_ratio > 0)
{
var reflection_direction = ray.Dir + (normal * 2 * rayNormDot * (-1.0f));
Ray r;
r.Org = point_of_hit + (normal * 1e-5f);
r.Dir = reflection_direction;
var reflection = trace(r, scene, depth + 1);
color += reflection * fresneleffect;
}
// compute refraction
if (depth < maxDepth && (obj.Transparency > 0))
{
var ior = 1.5f;
var CE = Vec3.Dot(ray.Dir, normal) * (-1.0f);
ior = inside ? (1.0f) / ior : ior;
var eta = (1.0f) / ior;
var GF = (ray.Dir + normal * CE) * eta;
var sin_t1_2 = 1 - (CE * CE);
var sin_t2_2 = sin_t1_2 * (eta * eta);
if (sin_t2_2 < 1)
{
var GC = normal * (Num)Math.Sqrt(1 - sin_t2_2);
var refraction_direction = GF - GC;
Ray r;
r.Org = point_of_hit - (normal * 1e-4f);
r.Dir = refraction_direction;
var refraction = trace(r, scene, depth + 1);
color += refraction * (1 - fresneleffect) * obj.Transparency;
}
}
return(color);
}
