private Vector3 CastRay(Ray ray, int depth = 0)
{
(float i1, float i2)minIntersection = (float.MaxValue, float.MaxValue);
IIntersectable minObj = null;
// find closest intersection if it exists
foreach (IIntersectable obj in objects)
{
(float i1, float i2)intersection = obj.Intersect(ray);
if (intersection.i1 > 0 && intersection.i1 < minIntersection.i1)
{
minIntersection = intersection;
minObj = obj;
}
}
if (minObj == null)
{
if (depth == 0)
{
return(BackgroundColour);
}
else
{
return(new Vector3(0));
}
}
Vector3 iPoint = ray.ToPoint(minIntersection.i1);
Vector3 iNormal = minObj.CalcNormal(iPoint, true);
Vector3 pointCol = minObj.Colour * minObj.Ambient;
foreach (Light light in lights)
{
// cast shadow ray for each object. if collide, shadow
Vector3 il = (light.Pos - iPoint).Normalized();
Ray ilRay = new Ray(iPoint + iNormal, il);
bool shadow = false;
foreach (IIntersectable obj in objects)
{
if (obj.Intersect(ilRay).i1 > 0)
{
shadow = true;
break;
}
}
// calculate actual lighting if not in shadow
// based on https://en.wikipedia.org/wiki/Phong_reflection_model and https://en.wikipedia.org/wiki/Blinn%E2%80%93Phong_reflection_model
if (!shadow)
{
float angleCoeff = Math.Max(0f, Vector3.Dot(il, iNormal));
Vector3 diffuse = minObj.Colour * angleCoeff * light.Brightness * minObj.Diffuse;
Vector3 lv = il - ray.Dir;
Vector3 h = lv / lv.Length;
float nh = Math.Max(0f, Vector3.Dot(iNormal, h));
Vector3 specular = minObj.SpecularColour * (float)Math.Pow(nh, minObj.Shininess) * minObj.Specular;
pointCol += diffuse * specular;
}
// handle reflective materials
if (minObj.Reflectivity > 0 && depth < 5)
{
Vector3 rVec = (il - 2 * Vector3.Dot(il, iNormal) * iNormal).Normalized();
Ray subRay = new Ray(iPoint + iNormal, rVec);
Vector3 rColour = CastRay(subRay, depth + 1);
pointCol += rColour * minObj.Reflectivity;
}
}
return(pointCol);
}
