fix equirectangular projection

1 files changed, 31 insertions, 26 deletions

diff --git a/src/classes/cubemap.rs b/src/classes/cubemap.rs
index 0355a05..58e77d6 100644
--- a/src/classes/cubemap.rs
+++ b/src/classes/cubemap.rs
@@ -4,6 +4,7 @@ use anyhow::Result;
 use glam::{UVec2, Vec3Swizzles, uvec2, vec2, vec3};
 use image::{DynamicImage, ImageBuffer, Rgba};
 use log::info;
+use rayon::iter::ParallelIterator;
 use serde::Serialize;
 use std::f32::consts::PI;
 
@@ -38,35 +39,39 @@ pub fn cubemap_to_equirectangular(
         faces[0].height()
     );
     let mut output_image = ImageBuffer::<Rgba<f32>, Vec<f32>>::new(output_width, output_height);
-    for (er_x, er_y, out) in output_image.enumerate_pixels_mut() {
-        let xy_angle = er_x as f32 / output_width as f32 * PI * 2.;
-        let cyl_z = er_y as f32 / output_height as f32 * 2. - 1.;
-        let sphere_azimuth = cyl_z.asin();
-        let r = sphere_azimuth.cos();
-        let normal = vec3(xy_angle.sin() * r, xy_angle.cos() * r, cyl_z);
-        assert!(normal.is_normalized());
+    output_image
+        .par_enumerate_pixels_mut()
+        .for_each(|(er_x, er_y, out)| {
+            let phi = er_x as f32 / output_width as f32 * PI * 2.;
+            let theta = (1. - er_y as f32 / output_height as f32) * PI;
+            let normal = vec3(
+                phi.sin() * theta.sin(),
+                phi.cos() * theta.sin(),
+                theta.cos(),
+            );
+            assert!(normal.is_normalized());
 
-        let normal_abs = normal.abs();
-        let (axis, max_comp, other_comps) = if normal_abs.x > normal_abs.y.max(normal_abs.z) {
-            (0, normal.x, normal.yz())
-        } else if normal_abs.y > normal_abs.z {
-            (1, normal.y, normal.xz())
-        } else {
-            (2, normal.z, normal.xy())
-        };
+            let normal_abs = normal.abs();
+            let (axis, max_comp, other_comps) = if normal_abs.x > normal_abs.y.max(normal_abs.z) {
+                (0, normal.x, normal.yz())
+            } else if normal_abs.y > normal_abs.z {
+                (1, normal.y, normal.xz())
+            } else {
+                (2, normal.z, normal.xy())
+            };
 
-        let face = axis as usize * 2 + if max_comp < 0. { 1 } else { 0 };
-        let face_texture = &faces[face];
-        let face_size = uvec2(face_texture.width(), face_texture.height());
-        let face_uv = other_comps / max_comp * vec2(1., -max_comp.signum());
-        let face_uv = face_uv / 2. + 0.5;
+            let face = axis as usize * 2 + if max_comp < 0. { 1 } else { 0 };
+            let face_texture = &faces[face];
+            let face_size = uvec2(face_texture.width(), face_texture.height());
+            let face_uv = other_comps / max_comp * vec2(1., -max_comp.signum());
+            let face_uv = face_uv / 2. + 0.5;
 
-        let face_xy = (face_uv * face_size.as_vec2())
-            .floor()
-            .as_uvec2()
-            .clamp(UVec2::MIN, face_size - UVec2::ONE);
+            let face_xy = (face_uv * face_size.as_vec2())
+                .floor()
+                .as_uvec2()
+                .clamp(UVec2::MIN, face_size - UVec2::ONE);
 
-        out.0 = face_texture.get_pixel(face_xy.x, face_xy.y).0;
-    }
+            out.0 = face_texture.get_pixel(face_xy.x, face_xy.y).0;
+        });
     output_image
 }