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Fix issue with noise in refrections 

The BSDF for Reflective material had rounding issues that would
sometimes make the reflection strength NaN.
This commit is contained in:
Matthew Gordon 2019-11-30 11:26:18 -05:00
parent d19d5200b0
commit 6f1663f616
1 changed files with 9 additions and 5 deletions
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14
src/materials.rs
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@ -1,4 +1,4 @@
use nalgebra::{convert, RealField, Vector3};
use nalgebra::{clamp, convert, RealField, Vector3};
use super::colour::{ColourRgbF, NamedColour};
@ -88,11 +88,15 @@ impl<T: RealField> Material<T> for ReflectiveMaterial<T> {
let reflection_vector = Vector3::new(-w_o.x, -w_o.y, w_o.z);
let reflection_colour = colour_in * self.reflection_strength;
let diffuse_colour = self.colour * colour_in * self.diffuse_strength;
let sigma: T = convert(0.001);
let sigma: T = convert(0.05);
let two: T = convert(2.0);
let reflection_factor = (-w_i.dot(&reflection_vector).acos().powf(two)
/ (two * sigma * sigma))
.exp();
// These are normalized vectors, but sometimes rounding errors cause the
// dot product to be slightly above 1 or below 0. The call to clamp
// ensures the values stay within the domain of acos,
let theta = clamp(w_i.dot(&reflection_vector), T::zero(), T::one())
.abs()
.acos();
let reflection_factor = (-(theta.powf(two)) / (two * sigma * sigma)).exp();
reflection_colour * reflection_factor
+ diffuse_colour * (T::one() - reflection_factor)
}