No noticeable improvement with denoise.exe

[ted-kapustin]

I tried using denoise.exe with raytraced images that I generated with Blender. I tried it with images generated using 64, 32, 16, 8, 4, 2, and 1 samples per pixel. There was no noticeable improvement of the image's quality. Moreover, the source and output images look identical (they both have "salt and pepper" look). However, when I use ImageMagick's compare utility, it shows some subtle differences. I generated 24-bpp (8 bits per channel) sample images (I saved them in BMP format) from Classroom sample scene available on Blender Web site. I then converted BMP files to PFM using my own program, then used them as input files with -ldr option, and then converted output images to BMP using my other program. All images have 3840x2160 dimensions.

Am I doing something wrong, or maybe something is wrong with the program?

I am on 64-bit Windows 10. I can share the code of my program that converts BMP to PFM if necessary.

[atafra]

Open Image Denoise works only with images which have no post-processing applied (e.g. distortions). AFAIK the Blender Classroom scene does have some kind of post-processing, which causes the denoising to fail. The post-processing needs to be applied after denoising. This is why denoising ideally should be integrated into a renderer, and not used separately. The included example (denoise) was not intended to be used as an end-user application. It's only a tutorial for developers who would like to integrate the denoiser into a renderer.