fix coordinates in generate_fft_reference.py

1 files changed, 8 insertions, 1 deletions

diff --git a/generate_fft_reference.py b/generate_fft_reference.py
index a7d58f4..db2289d 100644
--- a/generate_fft_reference.py
+++ b/generate_fft_reference.py
@@ -18,10 +18,13 @@ def main():
 
     # Load input image and convert to luminance
     img = Image.open(args.input).convert('RGB')
-    img = img.resize((args.size, args.size), Image.Resampling.LANCZOS)
+    img = img.resize((args.size, args.size), Image.Resampling.NEAREST)
     img_array = np.array(img, dtype=np.float32) / 255.0
     luminance = 0.2126 * img_array[:,:,0] + 0.7152 * img_array[:,:,1] + 0.0722 * img_array[:,:,2]
 
+    # Unity's UV origin is bottom-left, NumPy/PIL's is top-left; flip vertically to align
+    luminance = np.flipud(luminance)
+
     # Perform 2D FFT (no fftshift, matching GPU implementation)
     fft_result = np.fft.fft2(luminance)
 
@@ -30,6 +33,10 @@ def main():
     real_part = fft_result.real.astype(np.float32)
     imag_part = fft_result.imag.astype(np.float32)
 
+    # Unity's output texture also uses bottom-left origin, so flip output too
+    real_part = np.flipud(real_part)
+    imag_part = np.flipud(imag_part)
+
     # Create EXR
     height, width = args.size, args.size
     header = OpenEXR.Header(width, height)