Handling Surface Acne in section 12.6 seems wrong.

[jeffreyrosenbluth]

raytracing.github.io/src/common/color.h

Line 24 in 04d80ed

// Replace NaN components with zero. See explanation in Ray Tracing: The Rest of Your Life.

Replacing NaNs here with 0.0 will simply replace a pixel with one thats the wrong color. E.g. rgb = (NaN, Nan, Nan) will be black in the final image. When I use the glass sphere in my cornell box I still get acne. As you describe in the text 'pixel_color' is the average over many samples so the NaN fix should take place before the averaging. Probably here:

raytracing.github.io/src/TheRestOfYourLife/scene.h

Line 34 in 04d80ed

ray r = cam.get_ray(u, v);

So that the black is averaged in. I tested this in my ray tracer which is written in Rust and it seems to work. Technically I think it would be better to just throw out this ray but this would require keeping track of the number of "good" rays to reduce the number of samples_per_pixel in the denominator.

[trevordblack]

I believe this was already fixed in the dev-major branch, but if not, an issue might be floating around for this somewhere.

[jeffreyrosenbluth]

The def-major branch still has this error. But you are right, issue 979 #979 (comment) discuss this problem

Thanks for the speedy response!

[trevordblack]

If I'm in a meeting at the office, you get a speedy response!

[hollasch]

Let's close this issue and consolidate discussion in #979.