Background Problem

[Chris]

Ultimately I don't think there is a bug here. While the behavior might be unexpected, it is actually how it should work. When you are rendering a parallel projection, it's kind of an "unnatural" viewpoint (objects don't decrease in size with distance). So trying to apply that viewpoint to the spherical sky simply doesn't work well. Even if the background did render, it would likely be extremely distorted.

When I tested, I got the same results regardless of whether the image was HDR or JPG. And it isn't the background color that you are seeing. I'm fairly certain it is a single pixel picked out of the background image. Probably the one directly opposite the viewpoint (again, the result of how the projection math works). If you move the view around and re-render, you will see the background changing color.

When using parallel projection, you are probably best off either using a solid color background or ensuring you have some sort of background plane geometry. As mentioned before, the "Background Image" sky settings do still work.

[ntxdave]

Thanks for the feedback Chris. I guess in the past most of my renders were of car wash tunnel equipment (the equipment your car passes through) and in those cases we wanted to show it with the parallel setting. I also used an indefinite plan which gave us the environment we wanted for those renders. So, I understand what you are saying will use the perspective setting for my other renders going forward.

The testing I did for this topic did also give some education though so it was not a total waste of time. Hope that maybe others will also learn something from the post I made.