Don't forget to execute the last loop in `compute_beam_diffusion_bssrdf()` in parallel:

[wahn]

Don't forget to execute the last loop in compute_beam_diffusion_bssrdf() in parallel:

pub fn compute_beam_diffusion_bssrdf(g: Float, eta: Float, t: &mut BSSRDFTable) {
...
    // ParallelFor([&](int i) {
    for i in 0..t.n_rho_samples as usize {
           // TODO: execute in parallel
...
    }
    // }, t.n_rho_samples);
}

Originally posted by @wahn in #84 (comment)

[wahn]

Don't expect a big performance impact by running that loop in parallel. The only time that function gets called is in the constructor of SubsurfaceMaterial:

impl SubsurfaceMaterial {                                                                               
    pub fn new(                                                                                         
        scale: Float,                                                                                   
        kr: Arc<Texture<Spectrum> + Sync + Send>,                                                       
        kt: Arc<Texture<Spectrum> + Sync + Send>,                                                       
        sigma_a: Arc<Texture<Spectrum> + Sync + Send>,                                                  
        sigma_s: Arc<Texture<Spectrum> + Sync + Send>,                                                  
        g: Float,                                                                                       
        eta: Float,                                                                                     
        u_roughness: Arc<Texture<Float> + Sync + Send>,                                                 
        v_roughness: Arc<Texture<Float> + Sync + Send>,                                                 
        bump_map: Option<Arc<Texture<Float> + Sync + Send>>,                                            
        remap_roughness: bool,                                                                          
    ) -> Self {                                                                                         
        let mut table: BssrdfTable = BssrdfTable::new(100, 64);                                         
        compute_beam_diffusion_bssrdf(g, eta, &mut table);                                              
...
    }                                                                                                   
...
}

[wahn]

After 5988adb commit we can measure the exact time for SubsurfaceMaterial::new():

> pwd
/mill3d/users/jan/git/gitlab/rs-pbrt-test-scenes/pbrt/sss_dragon
> time ~/git/github/rs_pbrt/target/release/rs_pbrt -i sss-dragon.pbrt 
pbrt version 0.6.2 [Detected 8 cores]
Copyright (c) 2016-2019 Jan Douglas Bert Walter.
Rust code based on C++ code by Matt Pharr, Greg Humphreys, and Wenzel Jakob.
Integrator "path"
  "integer maxdepth" [5]
Sampler "halton"
  "integer pixelsamples" [16]
Film "image"
  "integer xresolution" [1366]
  "integer yresolution" [1024]
  "float scale" [2]
PT0.233061136S seconds for SubsurfaceMaterial::new() ...
Rendering with 8 thread(s) ...
...

Let's see which time we will measure afterwards ...

[wahn]

Not really worth doing ... unless there is a test scene which states otherwise ...