public virtual List<ZBufferItem> Trace(Ray ray, Matrix transform, Vector3 translation)
{
var intersections = new List<ZBufferItem>();
foreach (var primitive in Triangles)
{
var items = primitive.Trace(ray, transform, translation);
intersections.AddRange(items);
}
return intersections;
}
/// <summary>
/// Get the colour at this point on this triangle
/// </summary>
public Color Colorise(Scene scene, Shapes.Ray ray, Matrix transform, Vector3 translation, Vector3 intersection)
{
var colour = new Color();
foreach (var light in scene.Lights)
{
// get the vector between the light and the point
var lightv = Vector3.Normalize(intersection - light.Position);
var distance = Vector3.Distance(intersection, light.Position);
// get the texture colour
var a = Shader.Ambient(light, distance);
colour += a;
var lightraydir = light.Position - intersection;
lightraydir.Normalize();
// don't intersect with the object i'm on
var lightrayorigin = intersection + 0.01f*lightraydir;
var lightray = new Ray(lightrayorigin, lightraydir);
var lightx = scene.Trace(lightray, transform, translation);
if (!lightx.Any())
{
var l = Shader.Lambertian(Normal, light, lightv, distance);
var s = Shader.Specular(Normal, ray.Direction, light, lightv, distance);
colour += l;
colour += s;
}
}
return colour;
}
/// <summary>
/// Möller–Trumbore ray-triangle intersection algorithm
/// </summary>
/// <param name="ray">ray to test</param>
/// <param name="transform">world rotation transform</param>
/// <param name="translation">translation vector</param>
/// <returns>list of intersections</returns>
public List<ZBufferItem> Trace(Ray ray, Matrix transform, Vector3 translation)
{
var buffer = new List<ZBufferItem>();
var ts = Vertices.Select(vertex => Vector3.TransformCoordinate(vertex, transform)).Select(vertex => vertex + translation).ToArray();
// find vectors for two edges sharing ts[0]
var edge1 = ts[1] - ts[0];
var edge2 = ts[2] - ts[0];
var cross = Vector3.Cross(ray.Direction, edge2);
var det = Vector3.Dot(edge1, cross);
// if det is near 0 then ray is in the plane of the triangle i.e. parallel
if (det > -float.Epsilon && det < float.Epsilon)
{
return buffer;
}
var invDet = 1f/det;
var T = ray.Origin - ts[0];
var u = Vector3.Dot(T, cross)*invDet;
// if u is not 0->1 then intersection is outside the triangle
if (u < 0f || u > 1f)
{
return buffer;
}
var Q = Vector3.Cross(T, edge1);
var v = Vector3.Dot(ray.Direction, Q)*invDet;
// then intersection is outside the triangle
if (v < 0f || u + v > 1f)
{
return new List<ZBufferItem>();
}
var t = Vector3.Dot(edge2, Q)*invDet;
// ray intersection!
if (t > float.Epsilon)
{
// get the point of intersection
var ix = ray.Origin + t*ray.Direction;
buffer.Add(new ZBufferItem(this, ix, translation));
}
return buffer;
}
public Color Colorise(Scene scene, Ray ray, Matrix transform, Vector3 translation, Vector3 intersection)
{
// this is never called
return Color.BlanchedAlmond;
}
private Color TraceRay(Matrix transform, int x, int y, int width, int height)
{
var camPositionScaled = Vector3.Divide(_scene.Camera.Position, _scene.Camera.Scale);
// work out the orientation of the image plane
var camDir = _scene.Camera.Target - camPositionScaled;
var xDir = Vector3.Cross(Vector3.UnitY, camDir);
var yDir = Vector3.Cross(camDir, xDir); // now correct the up dir
camDir.Normalize();
xDir.Normalize();
yDir.Normalize();
// now get the uv coordinates on our image plane, scaled by unitsize
const float unitsize = 0.1f;
var u = (float)((x - 0.5 * width) * unitsize);
var v = (float)((y - 0.5 * height) * unitsize);
// now move u units along x, v units along y, starting at camposition
var uv = camPositionScaled + u * xDir + v * yDir;
// now the direction of the ray from uv to the target
var rayDir = _scene.Camera.Target - uv;
rayDir.Normalize();
// get the actual ray
var ray = new Shapes.Ray(uv, rayDir);
var bounces = new List<ZBufferItem>();
const int iterations = 2;
for (var i = 0; i < iterations; i++)
{
var items = _scene.Trace(ray, transform, _scene.Origin);
if (items.Any())
{
var closest = items.OrderByDescending(d => d.Distance(ray.Origin)).First();
bounces.Add(closest);
if (closest.Primitive.Shader.IsReflective)
{
var reflectedRay = -ray.Direction -
2*Vector3.Dot(-ray.Direction, closest.Primitive.Normal)*
closest.Primitive.Normal;
reflectedRay.Normalize();
// don't want to intersect the reflection plane
var reflectionOrigin = closest.Intersection + 0.01f*reflectedRay;
ray = new Shapes.Ray(reflectionOrigin, reflectedRay);
//var reflections = _scene.Trace(ray, transform, _scene.Origin);
//if (reflections.Any())
//{
// bounces.Add(reflections.OrderByDescending(d => d.Distance(ray.Origin)).First());
//}
}
}
}
if (bounces.Any())
{
var c = new Color();
foreach (var bounce in bounces)
{
var closestColour = bounce.Primitive.Colorise(_scene, ray, transform, bounce.Translation, bounce.Intersection);
var avgColour = Color.Scale(closestColour, 1f/bounces.Count);
c += avgColour;
}
c.A = 255;
return c;
}
return _scene.Ambient();
}