public static Vec trace(Vec origin, Vec direction)
{
var hitPoint = new Vec(0, 0, 0);
var normal = new Vec(0, 0, 0);
var result = new Vec(0, 0, 0);
double attenuation = 1.0;
var newDirection = new Vec(direction.x, direction.y, direction.z);
var newOrigin = new Vec(origin.x, origin.y, origin.z);
for (int bounceCount = 3; bounceCount > 0; --bounceCount)
{
Hit hitType = rayMarching(newOrigin, newDirection, ref hitPoint, ref normal);
if (hitType == Hit.None)
{
break;
}
if (hitType == Hit.Figure) // Specular bounce on a letter. No color acc.
{
newDirection.minusM(normal.times(normal.dot(newDirection) * 2.0));
newOrigin = hitPoint.plus(newDirection.times(0.1));
attenuation *= 0.2;
}
else if (hitType == Hit.Wall)
{
double incidence = normal.dot(lightDirection);
double p = 6.283185 * rnd.NextDouble();
double c = rnd.NextDouble();
double s = Math.Sqrt(1.0 - c);
double g = normal.z < 0 ? -1 : 1;
double u = -1 / (g + normal.z);
double v = normal.x * normal.y * u;
Vec a = new Vec(v, g + normal.y * normal.y * u, -normal.y);
a.timesM(s * Math.Cos(p));
Vec b = new Vec(1 + g * normal.x * normal.x * u, g * v, -g * normal.x);
b.timesM(s * Math.Sin(p));
newDirection = a;
newDirection.plusM(b);
newDirection.plusM(normal.times(Math.Sqrt(c)));
newOrigin = hitPoint.plus(newDirection.times(0.1));
attenuation *= 0.2;
var ptAbove = hitPoint.plus(normal.times(0.1));
if (incidence > 0)
{
var tmp = rayMarching(ptAbove, lightDirection, ref hitPoint, ref normal);
if (tmp == Hit.Sun)
{
result.plusM(colorWall.times(attenuation * incidence));
}
}
}
else if (hitType == Hit.Sun)
{
result.plusM(colorSun.times(attenuation));
break;
}
}
return(result);
}
public static Hit rayMarching(Vec origin, Vec direction, ref Vec hitPos, ref Vec hitNorm)
{
Hit hitType = Hit.None;
int noHitCount = 0;
double d = 0.0; // distance from the closest object in the world.
for (double totalD = 0; totalD < 100; totalD += d)
{
hitPos = origin.plus(direction.times(totalD));
d = queryDatabase(hitPos, ref hitType);
if (d < 0.01 || ++noHitCount > 99)
{
Hit temp = Hit.None;
double normX = queryDatabase(hitPos.plus(dX), ref temp) - d;
double normY = queryDatabase(hitPos.plus(dY), ref temp) - d;
double normZ = queryDatabase(hitPos.plus(dZ), ref temp) - d;
hitNorm = (new Vec(normX, normY, normZ)).normalize();
return(hitType);
}
}
return(Hit.None);
}
