View Full Version : Reflection Bug

04-20-2009, 08:12 PM
Hey guys, i'm trying to composite some red cubes into live footage for some of our station IDs, and i'm getting some really weird bugs with the reflections.

I've rendered out a test on on black so you can see exactly what the reflections are doing.

The version of lightwave is 9.3 on a MacPro 8core with OSX10.5.4

I have absolutely no clue whats going on. Never seen it do this before. Any ideas?

04-20-2009, 11:38 PM
3D allows you to create anything you can imagine, so we have no idea what this is supposed to look like. It looks like the ground has bump in it, is that intentional or is that the error? The background not reflecting in the floor - is that the error? The long reflection from the farthest cube - is it reflection blur, or is that the error?

04-20-2009, 11:52 PM
Background image? It can't be reflected if that's the case, you need to apply the image to a polygon to see it in reflection.

04-21-2009, 12:44 AM
3D allows you to create anything you can imagine within the limits of 3D geometry.

There is supposed to be a bump map.

I have made it so the background isn't reflected as its being composited into live action footage of floodwater with real world reflections i don't want the sky to be re-reflected.

There is no reflection blur.

The problem is the weird diagonal artifacts (Most evident on the furthest cube.) This should not be happening, but for some reason it is....

Simply put (lens bending, smooth shading, Einsteins laws of space time curvature, etc aside), reflective polygons are based on a liner incidence bounce between the object and the lens. With a flat floor plane such as this (even with the bumpmap) the reflections should be running more or less strait in the direction of the camera lens not off to the side.

04-21-2009, 02:39 AM
What kind of bump is it, texture map or procedural, what are the settings like? Bump is a complete cheat, so it wouldn't surprise me if that was the cause.

04-21-2009, 05:50 PM
Bump map is a collection of procedurals.

Turbulent procedural with a bunch of ripples laid over the top with gradual falloffs from the center of the cubes.

Its quite probable that it is the bump map causing it.
Turning them all off renders with fairly strait reflections (Though its very hard to tell, the cube reflection on the bottom right doesn't look right to me, but it could just be artificial lens bending as its so close to edge of frame?)
Turning any one of them back on makes it all go haywire again.

But i've never seen it do this before. I mean one of the first exercises that any noob undertakes in the 3d world is the old sun specular reflecting off a flat procedural ocean. This is basically the same thing, I can't see why it would be doing this.

If it is the bump map and there no way around it short of turning off the bump, im kinda boned as i need the reflections to roughly match the real world ripples on the live footage.

04-21-2009, 06:14 PM
Hm, the settings look fine, and you don't have it set above 100% anywhere right? Well ripples *could* reflect off to the side if they're shaped right, just like anisotropy. Maybe increase the size of the ripples just in order to see if that's where the reflection is coming from? Or simply try a lot of bump without any ripples, see if it goes away.
If you can post your ground plane we can take a closer look at it too.

04-21-2009, 07:39 PM
Nothing peaks over 100%. And ripples have a fairly sharp falloff of about 5 metres (twice the width of the cubes), but its a moot point, As mentioned, any of the bump layers on their own seem to causing it.

Included a render with the full backdrop and groundplane. The only bump channel on this one is the turbulence. Problem still persists.

I'm starting to think i should cut my losses and just knock this one together with blender before i waste any more time on it.

04-21-2009, 08:03 PM
Damn it looks even more freaky now. I'm going to see if I can duplicate it when I get back home. Sorry we couldn't iron it out.

That sky looks f***ing awesome. Is it a part of the photo or did you add it?

04-21-2009, 08:25 PM
Nah, thats raw footage. We shot it in Normanton, Queensland not too long after the floods a couple of months ago

The camera used was a Sony XDCAM Prodisk PDW-700 with a Fujinon HD wide angle lens. Absolutely beautiful footage, and the Prodisk workflow is allot more pleasant to use than tapes.

Hopefully it will look even pretty once i've done the colour correction and what not.

Thanks for looking into it, but i wouldn't go to too much trouble. Think i'll just look for another way around it. I Don't relish the idea of using blender to do the job as its surface editor is so naff, but lightwave is just not working for this shot for some reason. Hmm, i think there might be an old copy of C4D floating around here somewhere too. That might be a better option...

04-21-2009, 09:33 PM
You won't believe this, I don't, but I couldn't reproduce this until I added the distance to camera gradient. The reflections immediately skewed. Tried distance to object with a null parented to the camera, no change.

The only logical justification I can think of is that the gradient value is getting applied to the bump and not just the other layers - when I used the gradient alone in the bump it does the same thing. Anyway, somehow the vectors are getting confused and distorting the normals that way. I cant think of a good way to replace the gradients except by using nodes, or you could try using the Falloff attribute in each layer, it'll fade the texture from the center of the object, which you could place yourself.

04-22-2009, 06:37 PM
Even with all the gradients and ripples deleted it the problem was happening.

I cleared the scene re-added the objects and low and behold the artifacts are gone (or at least reduced to a virtually unnoticeable level)

Guess there must have been some "**** up all my reflections" tickbox i must have accidently checked somewhere in the previous scene file...

*sigh* Computers can be so difficult at times...

04-22-2009, 07:03 PM
Oh snap...

well, looks like i'll be using something else then...

04-24-2009, 06:17 PM
It's still happening? I'm away from home for the next week and can't open that file