Flipping Normals

[timmatron]

Does anybody know if the "reflect on back side" option works with flipped normals? It sounds like the obvious answer, but I think I tried it once before and nothing happened.

[instinct]

I didnt have any noticable speed decreasings with using that way. Dimo´s way also does the trick usually (we´re at the same company )

Thorsten

[timmatron]

Does anybody know if the "reflect on back side" option works with flipped normals? It sounds like the obvious answer, but I think I tried it once before and nothing happened.

Wow... I just tried it again, and it actually does work! There seemed to be a couple buggy things about it, but overall it seems like it could fix a large portion of the normals problems.

[arobbert]

I'm using 1.09 with VIZ 4 and brought in an autocad model, applied a basic vray mat double sided and force two sided on the problem is plainly visable. Back facing normals render wrong.

[arobbert]

This is a problem with 1.09. If I use the latest build the problem is fixed. I'd switch except that I've found the Vray light shadows in the new builds to be noisy unless I jack up the samples (like 4 which really slows things down.

[timmatron]

Has anybody been able to experiment with this lately?

On a project I was working on today, I had a surface that apparently had some flipped normals. I had 'force 2 sided' check in the max render options, and of course the flipped normals rendered, but without reflections. So then I checked 'render on back side' in the vray material options and rendered again, with the same results - no reflection on the flipped normals.

THEN, I uncheck 'force 2 sided' and rendered it again with 'reflect on back side' still checked, and voila!, a perfectly smoothed, rendered, and reflecting surface! I couldn't believe it. It seems that in some cases, the 'force 2 sided' option may be sabotaging the vray material settings. Unfortanately I didn't have all day to spend on testing, so I'm wondering if anybody else can try this out to see if I am on to something.

[elektrosport]

Just to vent my anger..

Geometry should always be flawless, closed and perfect! Flipped normals are usually seen when geometry is "corrupt".

At courses at school, when taught how to bridge from ACAD to MAX/VIZ this issue is addressed and solved with the force 2 sided "trick".. In my world this is blasphemy!
Also the "reflect on back side" should only be used when appropriate, not to fix amateurishly modelled geometry.

Both are poor solutions to poor modelling and from my experience it can mess you up good during your schedule and set you back a good couple of hours of error-hunting, remodelling, texturing and what not.

To say the least I'm extremely paranoid when it comes to recieving geometry from other people than me, myself, and I, especially if imported from ACAD. I prefer to model everything myself in Max from ACAD-imported plans, sections and elevations, this way I'm in complete control.

..But then again I am a control freak and I do come from a strict upbringing in the games industry. 12 years ago when low poly was _LOW_ poly and the 3DS 4 scanline renderer was "slightly" less developed, things really had to be correct or you'd have nothing.

Come to think of it, I may actually enjoy perfect geometry a lot more than good renders, maybe it's because there's really far between the really good renders that I've completely forgotten the experience or I may just be a sad person, but I guess this is another topic for another day?

Grumpy old man closing vent and signing off..


Cheers,
K.

[elektrosport]

One more thing to say:

_STL check_, a valuable tool not to be forgotten!


cheers,
K.

[Clifton Santiago]

This may sound too prescriptive, but my solution for your problem is to learn to model in MAX. I receive crappy cad models all the time and as a rule I re-model them in Max so I never have any of these problems. And I have yet to receive a cad model from an architect that I can't remodel in 2 or 3 hours (even if it took them 2 weeks to model in microstation)

[plastic_]

ok here is what i do...
usually the geometry with the flipped normals is a flat large area, converted autocad hatches.
a fast way to orient all normals to the top is viewing it from the bottom direction, enable "ignore backfacing", select the whole mesh with the rectangular selection tool.
that way only the polys with normals down are selected and it's easy to flip them with the "flip normals" button.
works much better than unify for large flat areas.

[instinct]

The two last posts apply to archviz mainly tho...try remodelling a car dataset...interior...with every nut and bolt in there...you´ll soon look for other ways around it :P

[timmatron]

I agree with what all of you say about the modeling being the core issue. But I just thought others who experience the same frustrations could benefit from this workaround as well.

[instinct]

In addition there are cases were max is not an option. If you need class-a surfaces...nevermind max :P

Thorsten

[Giovanni]

Last time I had a model with normals all over the places, it did not help to mess around with on/two sides, or the normals.

Just applting a shell modifier with zero depth, however, made the model perfectly renderable.


regards

gio

[DaForce]

wouldnt a shell mod with zero depth cause a shit load of coplanar faces?