/// <summary>
/// this method tests for an intersection. It will try to find the closest
/// object that intersects with the ray.
/// it will inspect every object in the scene. also here there is room for increased performance.
/// </summary>
/// <param name="ray"></param>
/// <param name="scene"></param>
/// <param name="exclude"></param>
/// <returns></returns>
private IntersectInfo TestIntersection(Ray ray, Scene scene, IShape exclude)
{
var hitcount = 0;
var best = new IntersectInfo()
{
Distance = double.MaxValue
};
foreach (var elt in scene.Shapes)
{
if (elt == exclude)
{
continue;
}
var info = elt.Intersect(ray);
if (info.IsHit && info.Distance < best.Distance && info.Distance >= 0)
{
best = info;
hitcount++;
}
}
best.HitCount = hitcount;
return(best);
}
/// <summary>
/// This is the main RayTrace controller algorithm, the core of the RayTracer
/// recursive method setup
/// this does the actual tracing of the ray and determines the color of each pixel
/// supports:
/// - ambient lighting
/// - diffuse lighting
/// - Gloss lighting
/// - shadows
/// - reflections
/// </summary>
/// <param name="info"></param>
/// <param name="ray"></param>
/// <param name="scene"></param>
/// <param name="depth"></param>
/// <returns></returns>
private Vector RayTrace(IntersectInfo info, Ray ray, Scene scene, int depth)
{
// calculate ambient light
var color = info.Color * scene.Background.Ambience;
// Console.WriteLine($"color ({color}) from info.color({info.Color})");
var shininess = Math.Pow(10, info.Element.Material.Gloss + 1);
foreach (var light in scene.Lights)
{
// calculate diffuse lighting
var v = (light.Position - info.Position).Normalize();
if (scene.RenderDiffuse)
{
var l = v.DotProduct(info.Normal);
if (l > 0.0f)
{
color += info.Color * light.Color * l;
}
}
// this is the max depth of raytracing.
// increasing depth will calculate more accurate color, however it will
// also take longer (exponentially)
if (depth < _traceDepth)
{
// calculate reflection ray
if (scene.RenderReflection && info.Element.Material.Reflection > 0)
{
var reflectionray = GetReflectionRay(info.Position, info.Normal, ray.Direction);
var refl = TestIntersection(reflectionray, scene, info.Element);
if (refl.IsHit && refl.Distance > 0)
{
// recursive call, this makes reflections expensive
refl.Color = RayTrace(refl, reflectionray, scene, depth + 1);
}
else // does not reflect an object, then reflect background color
{
refl.Color = scene.Background.Color;
}
color = color.Blend(refl.Color, info.Element.Material.Reflection);
}
//calculate refraction ray
if (scene.RenderRefraction && info.Element.Material.Transparency > 0)
{
var refractionray = GetRefractionRay(info.Position, info.Normal, ray.Direction, info.Element.Material.Refraction);
var refr = info.Element.Intersect(refractionray);
if (refr.IsHit)
{
//refractionray = new Ray(refr.Position, ray.Direction);
refractionray = GetRefractionRay(refr.Position, refr.Normal, refractionray.Direction, refr.Element.Material.Refraction);
refr = TestIntersection(refractionray, scene, info.Element);
if (refr.IsHit && refr.Distance > 0)
{
// recursive call, this makes refractions expensive
refr.Color = RayTrace(refr, refractionray, scene, depth + 1);
}
else
{
refr.Color = scene.Background.Color;
}
}
else
{
refr.Color = scene.Background.Color;
}
color = color.Blend(refr.Color, info.Element.Material.Transparency);
}
}
var shadow = new IntersectInfo();
if (scene.RenderShadow)
{
// calculate shadow, create ray from intersection point to light
var shadowray = new Ray(info.Position, v);
// find any element in between intersection point and light
shadow = TestIntersection(shadowray, scene, info.Element);
if (shadow.IsHit && shadow.Element != info.Element)
{
// only cast shadow if the found interesection is another
// element than the current element
color *= 0.5 + 0.5 * Math.Pow(shadow.Element.Material.Transparency, 0.5); // Math.Pow(.5, shadow.HitCount);
}
}
// only show highlights if it is not in the shadow of another object
if (scene.RenderHighlights && !shadow.IsHit && info.Element.Material.Gloss > 0)
{
// only show Gloss light if it is not in a shadow of another element.
// calculate Gloss lighting (Phong)
var lv = (info.Element.Position - light.Position).Normalize();
var e = (scene.Camera.Position - info.Element.Position).Normalize();
var h = (e - lv).Normalize();
var glossweight = 0.0;
glossweight = Math.Pow(Math.Max(info.Normal.DotProduct(h), 0), shininess);
color += light.Color * (glossweight);
}
}
return(color);
}
