59 lines
1.3 KiB
Rust
59 lines
1.3 KiB
Rust
//! Utilities for handling floating point precision issues
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//!
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//! This is based on the work in section 3.9 of "Physically Based Rendering:
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//! From Theory to Implementation" 3rd edition by Pharr et al.
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use crate::math::{dot, Normal, Point, Vector};
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pub use rmath::utils::{decrement_ulp, increment_ulp};
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#[inline(always)]
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pub fn fp_gamma(n: u32) -> f32 {
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use std::f32::EPSILON;
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let e = EPSILON * 0.5;
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(e * n as f32) / (1.0 - (e * n as f32))
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}
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pub fn robust_ray_origin(pos: Point, pos_err: f32, nor: Normal, ray_dir: Vector) -> Point {
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// Get surface normal pointing in the same
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// direction as ray_dir.
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let nor = {
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let nor = nor.into_vector();
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if dot(nor, ray_dir) >= 0.0 {
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nor
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} else {
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-nor
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}
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};
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// Calculate offset point
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let d = dot(nor.abs(), Vector::new(pos_err, pos_err, pos_err));
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let offset = nor * d;
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let p = pos + offset;
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// Calculate ulp offsets
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let x = if nor.x() >= 0.0 {
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increment_ulp(p.x())
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} else {
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decrement_ulp(p.x())
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};
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let y = if nor.y() >= 0.0 {
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increment_ulp(p.y())
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} else {
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decrement_ulp(p.y())
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};
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let z = if nor.z() >= 0.0 {
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increment_ulp(p.z())
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} else {
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decrement_ulp(p.z())
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};
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Point::new(x, y, z)
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}
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// #[cfg(test)]
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// mod tests {
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// use super::*;
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// }
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