DOF and mirrors

kesh

In some test renders (with daz studio 3dlight) i have noticed that Depth of Field produces a wrong effect when rendering reflected parts of scenes. The reflection is projected onto the mirroring surface and then DoF kicks in, so, if the mirror surface is in the 'in-focus' range, also all that's visible in the mirror gets rendered in focus, loosing infact the blurring that far objects (out of the focus range) should have.

Is there a way to avoid this, maybe increasing/tweaking the raytracing parameters?

GrokDD

As we all want to do things in one render pass, I feel for you.

However, unless you're doing animation, I do not think it would take more than a few minutes to fake it in post render. Render a second image from a camera set from the mirror's perspective. Flip the image horizontally and mask the frame of the mirror.

We'll see what others say about in-render magic.

Richard Haseltine

Or render with two different DoF settings, place the blurred mirror layer over the main render, then erase or mask everything but he reflection. Edit: but that would work only if the reflected items were all at the same distance from the mirror, and so wanted the same blur. Sorry, not a useful suggestion.

Herald of Fire

If the reflection is within the focus range then it should be crisp. This is normal behavior. Remember that the light is bouncing off the reflected surface virtually unchanged, and therefore as long as the mirror is in focus, so too will the reflections be. A blurred reflection would seem more out of place in this instance.

To think about it in another way. Assuming you have a mirror to the left hand side reflecting something on the far wall. If you chose to, you could focus the camera on the far wall and retain that same detail. The reason is because the light itself isn't what changes in DoF, it's merely the focusing of that light.

Still, if you do want blurred reflections then there are ways to go about this. Either render it twice, or you can assign a blur using the UberSurface shaders which will make the reflection seem out of focus.

Scott Livingston

I ran into this issue with the attached image. Doesn't seem right to me...I think the reflections in the floor should be blurrier (think of the distance the light is traveling between the floor and the objects being reflected). Unfortunately I don't know what the solution is...just thought I'd post the image as an example.

Googled "Reflections and depth of field" and found the following article, which appears relevant, though the software is Lightwave: http://www.altyna.com/lw/DOFreflections.htm

Szark

As HoF mentioned above Uber Surface has Reflection Blur and and Reflection Blur Sampling functions. But use the Blur wisely as 1% will give you nice subtle bluring close up and more blurring the further back from the camera you go. Increasing Sampling is if you need finer detail in the blurring. Also it does increaase render times more than just using RayTrace Reflections by itself. But for me the wait is worth it.

This image has 1% blur on all of the surfaces. The floor is reflecting the sky but the blur and togther with a weaker reflection strength, 75% I think, gives a nice effect without to much sky reflection detali.

kesh

Thank you all for the prompt replies!

My main doubt was if i was doing something wrong or if it is the renderer that fails at it and by what i see, it's a common issue, to be solved only through postwork or faking the DoF via reflection blur. Well, it's something to be mentioned in a "what would you like to see in Daz studio 5" thread... ;)