func (self *SurfacePoint) Emission(toPosition Vector3f,
outDirection Vector3f,
isSolidAngle bool) Vector3f {
ray := toPosition.Sub(self.Position)
normal := self.Tri.Normal()
distance2 := ray.Dot(normal)
cosOut := outDirection.Dot(normal)
area := self.Tri.Area()
/* emit front face of surface only */
var mulval1, mulval2 float32
mulval1 = math32.Bool2Float(cosOut > 0.0)
if isSolidAngle {
/* with infinity clamped-out */
var divval, powval float32
powval = math32.Pow10(-6)
if distance2 >= powval {
divval = distance2
} else {
divval = powval
}
mulval2 = (cosOut * area) / divval
} else {
mulval2 = 1.0
}
solidAngle := mulval1 * mulval2
return self.Tri.Emitivity.Mulf(solidAngle)
}
func (self *SurfacePoint) Reflection(inDirection,
inRadiance,
outDirection Vector3f) Vector3f {
normal := self.Tri.Normal()
inDot := inDirection.Dot(normal)
outDot := outDirection.Dot(normal)
/* directions must be same side of surface (no transmission) */
isSameSide := !(math32.Xor(inDot < 0.0, outDot < 0.0))
/* ideal diffuse BRDF:
radiance sacaled by reflectivity, cosine and 1/pi */
r := inRadiance.Mulv(self.Tri.Reflectivity)
mulval1 := (math32.Abs(inDot) / math32.Pi)
mulval2 := math32.Bool2Float(isSameSide)
return r.Mulf(mulval1 * mulval2)
}