View Full Version : Reflection node - Mac bug?

08-11-2006, 02:38 AM
Sorry for the long post but this is a bit involved. I'm having some trouble with the reflection node which I'm beginning to suspect is a Mac bug. Here's what the manual says about connecting a reflection node;

"Typically this output is connected to the Reflection Shading input of the Surface destination node. However, it may also be used within a network when using this shading model for other purposes or when mixing several diffuse shading models together. "

So I set up a scene with an image in the background attach a reflection node to the reflection shading input (red) of the surface. Reflection shows on the preview of the reflection node but not on the surface preview. If I render there is no reflection.

If I attach the reflection node to the reflection input (green) I now get reflection in the surface preview and in the render. However reflection blurring is extreemly weak (barely noticeable) through the reflection input (green) unless I attach the reflection color of the reflection node to the reflection input (green) AND the reflection shading input (red) Remember the reflection shading input doesn't do anything on it's own.

If I attach the color output of the reflection node to the diffuse shading input of the surface I get ordinary and blurred reflection just as I would expect from the reflection shading input.

I'm pretty sure that it's not meant to work like this, not according to the manual anyway! Is this is how it works on Windows? Can any Mac users confirm this behavior? Is this a bug or am I just being terminally stupid again!? :D

Thanks for any help - Baz

08-11-2006, 03:17 AM
I'm pretty sure that it's not meant to work like this, not according to the manual anyway! Is this is how it works on Windows? Can any Mac users confirm this behavior? Is this a bug or am I just being terminally stupid again!? :D
None of the above - personally, I find a certain lack of uniformity with the way this works...

Reflection shading needs a value set for reflection - two other ways to describe it would be to say the reflection amount and the Reflection Shading are multiplied, or that the Reflection Shading replaces the way LW would ordinarily trace reflections, but is still considered "how reflections are computed" and the reflection amount will control how much to add to the surface.

Same goes for Refraction Shading, but not Diffuse Shading nor Specular Shading. Go figure, eh?

BTW, attaching the color output to the reflection amount dot basically uses what is being reflected as the amount of that reflection to add. :D Not something you'd want to do in most cases. Just set some value for reflection (eg. a Fresnel-style incidence gradient) and you'll see things start working...

08-11-2006, 03:35 AM
So I have to set reflection amount in THE LAYERS PANEL!???

I'm sorry but that's just insane, everything I've learned about nodes tells me it always overides the layers panel (Unless you have a layers node of course!) and now I find that sometimes nodes won't work without a value in the layers panel! 2/10 for consistancy guys! Just put a value slider in the reflection node for goodness sake!

Thanks Weepul, I might have stumbled across that eventuallly but I would NEVER have expected it to work that way! :(

08-11-2006, 03:44 AM
Well, you could connect a value to the refraction amount in the Node editor...like I said, a gradient, or you could simply use a Scalar value node...

The input to the Reflection scalar dot will override the classic surface editor values. It's just that you need a nonzero value there, however you do it.

08-11-2006, 03:57 AM
Thanks, yes I suppose that makes a little more sense but it's still very poor design in my opinion. A value slider in the reflection node is the only logical way, I'm sure there's some technical reason for the way it's set but users shouldn't have to worry about such things!

Anyway, rant over, at least it works which is the main thing but it ain't helping with the integrated and coherent LW that we're hoping for!

BTW Thanks again for your help! :D

08-13-2006, 03:23 AM
That completely confused me as well.

Turns out though, that the render times for blurred reflections. Are far too slow to be practical, on my dual 2.5 Mac at least.

08-13-2006, 05:19 AM
That's odd, I haven't done any intensive testing but they seem to be very quick to me and I have a very slow machine in comparrison. I did find the speed vary consideerably depending on how you set them up, with a reflection node plugged into reflection shading and a value or gradient plugged into reflection as Weepul suggests they seem pretty fast! I'll try and do some more formal tests and post results.

08-13-2006, 06:11 AM
Baz, have you tried using the test object linked to in this thread (http://www.newtek.com/forums/showthread.php?t=55246)

It has a lot of reflective planes, and for me, the difference in render time between non blurred and blurred, is just phenomenal.

08-13-2006, 09:16 AM
No I think that's beyond my poor old eMac! :D But with blurry reflections of blurry reflections I can understand big differences. I'm just about to try some tests of simple stuff to get an idea of how times compare so I'll let you know how I get on.

Cheers - Baz

08-13-2006, 09:55 AM
I just ran some simple tests, 75000 poly object a cube to act as a floor and an image in the background, 1 distant light, raytraced shadows and reflections

No reflection 5.1 secs
Nodal reflection 13 secs
Nodal reflection with 50% blur 61 secs

Take away the floor and the times are
No reflection 4.9 secs
Nodal reflection 8 secs
Nodal reflections with 50% blur 18 secs

So that second reflective surface really bumps up the render time!

That's with ray recursion set to 16, let me try lowering it a bit.

OK with the floor put back and ray recursion set to 4 the times are

Nodal reflection 11 secs
Nodal reflection with 50% blur 28.5 secs

With ray recursion set to 2 (Probably a bit to low, the render definately lacks depth)
Nodal reflection 10 secs
Nodal reflection with 50% blur 18.5 secs