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LDS sampling falls back on random sampling at higher dimensions.

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This is more a piece-of-mind thing than anything else.  But it
also lets us make the number of LDS dimensions lower without
worrying, which in turn makes the code smaller.
This commit is contained in:
Nathan Vegdahl 2017-05-14 16:06:54 -07:00
parent 322627641a
commit edb71864e8
2 changed files with 23 additions and 11 deletions
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30
src/renderer.rs
View File

@ -211,8 +211,8 @@ impl<'a> Renderer<'a> {
for si in 0..self.spp {
// Calculate image plane x and y coordinates
let (img_x, img_y) = {
let filter_x = fast_logit(halton::sample(4, offset + si as u32), 1.5) + 0.5;
let filter_y = fast_logit(halton::sample(5, offset + si as u32), 1.5) + 0.5;
let filter_x = fast_logit(get_sample(4, offset + si as u32), 1.5) + 0.5;
let filter_y = fast_logit(get_sample(5, offset + si as u32), 1.5) + 0.5;
let samp_x = (filter_x + x as f32) * cmpx;
let samp_y = (filter_y + y as f32) * cmpy;
((samp_x - 0.5) * x_extent, (0.5 - samp_y) * y_extent)
@ -223,9 +223,9 @@ impl<'a> Renderer<'a> {
&self.scene,
(x, y),
(img_x, img_y),
(halton::sample(0, offset + si as u32), halton::sample(1, offset + si as u32)),
halton::sample(2, offset + si as u32),
map_0_1_to_wavelength(halton::sample(3, offset + si as u32)),
(get_sample(0, offset + si as u32), get_sample(1, offset + si as u32)),
get_sample(2, offset + si as u32),
map_0_1_to_wavelength(get_sample(3, offset + si as u32)),
offset + si as u32,
);
paths.push(path);
@ -357,10 +357,9 @@ impl LightPath {
}
fn next_lds_samp(&self) -> f32 {
let s = halton::sample(self.dim_offset.get(), self.lds_offset);
let inc = self.dim_offset.get() + 1;
self.dim_offset.set(inc);
s
let dimension = self.dim_offset.get();
self.dim_offset.set(dimension + 1);
get_sample(dimension, self.lds_offset)
}
fn next(&mut self, xform_stack: &mut TransformStack, scene: &Scene, isect: &surface::SurfaceIntersection, ray: &mut Ray) -> bool {
@ -501,6 +500,19 @@ impl LightPath {
}
}
/// Gets a sample, using LDS samples for lower dimensions,
/// and switching to random samples at higher dimensions where
/// LDS samples aren't available.
#[inline(always)]
fn get_sample(dimension: u32, i: u32) -> f32 {
use hash::hash_u32_to_f32;
if dimension < halton::MAX_DIMENSION {
halton::sample(dimension, i)
} else {
hash_u32_to_f32(dimension, i)
}
}
#[derive(Debug)]
struct BucketJob {

4
sub_crates/halton/build.rs
View File

@ -29,7 +29,7 @@ use std::path::Path;
/// How many components to generate.
const NUM_DIMENSIONS: usize = 256;
const NUM_DIMENSIONS: usize = 128;
fn main() {
let out_dir = env::var("OUT_DIR").unwrap();
@ -194,7 +194,7 @@ fn halton2(mut index: u32) -> f32 {{
format!(
r#"
fn halton{}(index: u32) -> f32 {{
const PERM{}: [u16; {}] = [{}];"#,
static PERM{}: [u16; {}] = [{}];"#,
base,
base,
perm.len(),