Hello all,

I am having a problem with reflections ending up brighter than the object being reflected. Please see attachment showing both the render and the geometry. This is inside the boiler house of a toy steam engine. The bottom of the tank is seen above, a steam pipe coming down center and the tray for the fuel to the right. To the left, the inner wall of the house.

Everything is mia_material. The chrome of the tank, pipe and fuel-tray is the chrome preset - selected to see if I had changed something vital - and because it illustrates the problem well. There is an IBL node present to provide an environment for the chrome to reflect but which is otherwise invisible.

As you can see the reflection of the inner wall is far too bright.
Render settings are very basic. Increasing trace depth and reflections has no effect.

Can anyone point me in the right direction as to what might be the problem?
Is there something I am missing wrt. reflections when using mental ray?

Cheers,
Martin

Seasons greetings everyone.

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Hey,

Just poked my head in here, but I don’t actually see the problem? Are you referencing the missing (white) textures against the back wall?

Thank you for your interest Avotas.

I’ve tried posting the same pic and highlighting examples of what I mean:

Area A is a reflection of area B.
Area C is a reflection of area D.

As you can see, the reflections are much brighter than the object or area reflected.

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Mia_materials respect conservation of energy (the total reflected light cannot exceed the incoming light), so it seems that something else is going on here…

Are your objects/lights set to cast shadows?
Hard to diagnose from a couple screenshots though, are you able to post up the scene files?

n8skow [FA]

Thanks for the chart, now I can understand your problem. I agree with n8skow, we are going to need to see your scene file.

-Avotas

The comment by n8skow rang a bell because the lighting in the scene is so far just work-lights: 3 directional lights put there so I can see what I am doing. For a while now I have been trying to see if I could sort it out myself but it is beyond me.

Attached is the scene file - just about identical to how it was when I originally posted the problem. Only change is I have since then tweaked the base material (it was just a place-holder earlier) so it is not as brightly blue. Also I have removed a little of the shader tree from the brick housing material because I was using a color burn node I made myself and didn’t really know how to include it here.

It is a zip file which expands to ~10MB.

I am very interested to see if you can find what I am doing wrong. And obviously I hope it is not something too trivial and embarassing.

Cheers,
Martin

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steamengine.areapost.mb.zip

Got a chance to poke around your scene a bit here…

A few observations, it appears your rendering in ‘Draft’ quality - which is gonna affect the the brightness of the scene since your using so many raytraced materials/objects…

The 3 directional lights you refer to are not the only lighting in the scene - you also appear to be using Image Base Lighting (referencing a file named SM_HDRI-Pack1-22.hdr), but without having the file here - I can’t tell how it’s affecting your scene.

That brick shader your using on the walls appears to be somewhat complex - and it looks like all the effects aren’t being shown in the reflections - which is why I think it’s looking lighter…

n8skow [FA]

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I also spent some time poking around this scene (more time that I’m willing to confess...ok...at least 3 or 4 hours!) and I was not able to pin down the problem.  I exported the geometry and lights to a new scene and had the same problem.  I created some spheres and assigned a matte blinn to one and a reflective blinn to the other and I got similar results with the bright reflections.  But this seemed to not have the problem when I moved the spheres outside and into their own space.

So far, I’m stumped.

The shader setup for the bricks is extremely complicated and may be the source of the problem. But I can’t prove it yet… I didn’t even know you could do all that with those mental ray textures!

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

Thank you Valen Wagner and n8skow.

Yes - the brick texture is complex. It started out simple and I wasn’t really happy with it… and then I sort of got carried away. In part because someone posted a beautiful procedural mango shader on google plus and I thought I’d see how far I could go in that direction.

Valen Wagner: I am not sure I understand what you mean by “when I moved the spheres outside and into their own space”. Do you mean this is something that happens only underneath the boiler? Or something else?

I will continue to experiment. The point about the effects not really being reflected seems right and I will dig into that. I have made some tests with more physically correct lighting and I think I can get to a point where the problem is unnoticable - at least if I do not do a render from inside the boiler house. I can get it to a point where it is not noticable (or at least not alarming) from outside.

Also - attached here is the hdr.

Thank you again.

Martin

*EDIT* for some reason the hdr file won’t attach. I have put it here:

In you scene, raytrace shadow depth limit is low. Increas shadow depth in Render Setting->Quality->Raytracing->Shadows->6 (6 is minimum for best result). And for two directional lights set Ray Depth Limit to 6.

Thank you svv3d.

I just now discovered this too and found your answer when I was about to post.
Upping Raytrace Shadow Attributes->Ray Depth Limit on the lights fixed the problem.
(It never occurred to me that shadows also have a tracing depth till I read through every single setting).

Thank you all for your input. I am now a happy man.

Cheers,
Martin