Meowx Posted January 27, 2011 Posted January 27, 2011 Not so much a question, more just a cautionary tale! I was working on a character and noticed some rendering artifacts on a 5-point. Shift-1 and sure enough, normals were flipped the wrong way. Corrected it and then noticed that there were some MORE normals nearby in the neck facing the wrong way, too. Started fixing them and was surprised at how many there were. So, just to be safe, I went and turned off "show back facing polys." EEP. Embarrassingly, there were quite a few normals facing the wrong way. Extrusions in particular seemed to be pretty nasty. This got me wondering, so I went back and opened up a model I had finished a while back. My reaction: Sooo I've been fixing THAT whole model over the last hour. Remind me to turn off back facing polys more often! (Also, how accurate is it to just re-find normals? I was going to, but then I was like nah, don't want to go over the whole model again.) Before and after shots (animated gifs, cycling back and forth; click em if they don't work): Quote
Fuchur Posted January 27, 2011 Posted January 27, 2011 Hm... normally only backfacing normals of 5-pointers are bad. The rest should not really make a difference for rendering (if you are going to use it as a game-model it is something totally different...). Fine looking lady by the way! So back to extruding... it depends in which direction you extrude something... that will although determine, if the normals are facing in or out... Refind normals is not going to be very helpful... it is not for fixing "wrong" facing normals. For that there was a plugin from Steffen, which determined if normals should be flipped by the surrounding patches and their normals... it is not perfect but it can help! See you *Fuchur* Quote
HomeSlice Posted January 27, 2011 Posted January 27, 2011 I just leave "Show Backfacing Normals" off permanently. That way, I know where all my normals are facing all the time. Sometimes I will turn it on in a chor camera, but for modelling, it is always off. You never know when you are going to want to use a model you made months ago for some new dynamics/particle/cloth test. It's nice when you open an old model and all the normals are already facing the right way. Quote
Meowx Posted January 28, 2011 Author Posted January 28, 2011 Hm... normally only backfacing normals of 5-pointers are bad. The rest should not really make a difference for rendering (if you are going to use it as a game-model it is something totally different...). I don't know... I've noticed a very subtle difference in shading when normals are facing the other way. When two opposite flipped patches are next to each other, correcting it can actually be noticeable. Random lathe object; two renders: one with normals facing in, one with normals facing out. Subtle shading difference. (animated GIF) Quote
Fuchur Posted January 28, 2011 Posted January 28, 2011 Hm... normally only backfacing normals of 5-pointers are bad. The rest should not really make a difference for rendering (if you are going to use it as a game-model it is something totally different...). I don't know... I've noticed a very subtle difference in shading when normals are facing the other way. When two opposite flipped patches are next to each other, correcting it can actually be noticeable. Random lathe object; two renders: one with normals facing in, one with normals facing out. Subtle shading difference. (animated GIF) Interesting test... it is really a small difference and I am quite sure you would not notice it in normal situations, but it is there... *Fuchur* Quote
Hash Fellow robcat2075 Posted January 28, 2011 Hash Fellow Posted January 28, 2011 BTW, I had to click on it before it started cycling. Interesting that there is a difference. Too bad normals aren't like the fingers on an inside-out rubber glove where you could just blow into it and they all pop out. Quote
Fuchur Posted January 28, 2011 Posted January 28, 2011 BTW, I had to click on it before it started cycling. Interesting that there is a difference. Too bad normals aren't like the fingers on an inside-out rubber glove where you could just blow into it and they all pop out. Not a bad idea so... maybe it would be possible to write a plugin which uses a light and a radiosity-like cacluation to set all normals facing out... 1.) Put a light into the model. 2.) Let photons (a small amount) bounce around and where it hits a surface the normal should point to the inverted vector of the photon. It would only work with closed or nearly closed parts, but with only using a selection of points it could work out anyway. I'll do a featurerequest on that. Sounds like a nice idea. See you *Fuchur* Quote
Meowx Posted January 28, 2011 Author Posted January 28, 2011 Ha, cool idea! Would be neat to actually see it in action, too! Did the gifs in my original post work, Rob? They also cycle back and forth. What browser are you using? Quote
Hash Fellow robcat2075 Posted January 28, 2011 Hash Fellow Posted January 28, 2011 Did the gifs in my original post work, Rob? They also cycle back and forth. What browser are you using? Not until i clicked on them. Firefox 3.6 Quote
Meowx Posted January 28, 2011 Author Posted January 28, 2011 Huh, weird. Just tried it out (3.5.16), worked fine for me... I hate browsers. Getting stuff to work on every browser on every OS is a nightmare. Quote
NancyGormezano Posted January 28, 2011 Posted January 28, 2011 (edited) Huh, weird. Just tried it out (3.5.16), worked fine for me... I hate browsers. Getting stuff to work on every browser on every OS is a nightmare. FF 3.6.3 - even after clicking, didn't see a diff, I had to right click & choose "view image" to see. EDIT: I noticed the image is from modenstudios.com - perhaps if you uploaded gif to forum, it would work? However, I suspect would still have to click on it. Edited January 28, 2011 by NancyGormezano Quote
mtpeak2 Posted January 28, 2011 Posted January 28, 2011 Surprisingly, no one mentioned that normals determine the direction of displacement, bump and normal maps. Normals facing the wrong way will also cause issues when using the porcelain and hair/particle materials. Quote
Meowx Posted January 29, 2011 Author Posted January 29, 2011 See, this is why I like them all facing the same way. Quote
Hash Fellow robcat2075 Posted January 29, 2011 Hash Fellow Posted January 29, 2011 Always get your normals right. Quote
Hash Fellow robcat2075 Posted January 29, 2011 Hash Fellow Posted January 29, 2011 Surprisingly, no one mentioned that normals determine the direction of displacement, bump and normal maps. Normals facing the wrong way will also cause issues when using the porcelain and hair/particle materials. hey, mark, while you're in the building... http://www.hash.com/forums/index.php?showtopic=38968 Quote
markw Posted February 4, 2011 Posted February 4, 2011 I just leave "Show Backfacing Normals" off permanently. That way, I know where all my normals are facing all the time. Sometimes I will turn it on in a chor camera, but for modelling, it is always off. You never know when you are going to want to use a model you made months ago for some new dynamics/particle/cloth test. It's nice when you open an old model and all the normals are already facing the right way. Just found this thread and I like HomeSlice's idea to have "show back facing ploys/normals" turned to off when modeling but where do you find this option? I'v looked in Tools/Customise and then had a look in the TechRef manual but I'm still non the wiser. Quote
Fuchur Posted February 4, 2011 Posted February 4, 2011 I just leave "Show Backfacing Normals" off permanently. That way, I know where all my normals are facing all the time. Sometimes I will turn it on in a chor camera, but for modelling, it is always off. You never know when you are going to want to use a model you made months ago for some new dynamics/particle/cloth test. It's nice when you open an old model and all the normals are already facing the right way. Just found this thread and I like HomeSlice's idea to have "show back facing ploys/normals" turned to off when modeling but where do you find this option? I'v looked in Tools/Customise and then had a look in the TechRef manual but I'm still non the wiser. Go to tools - options - rendering. Switch from "final" to "shaded" mode. The setinng will appear in the list below. See you *Fuchur* Quote
Hash Fellow robcat2075 Posted February 4, 2011 Hash Fellow Posted February 4, 2011 Just found this thread and I like HomeSlice's idea to have "show back facing ploys/normals" turned to off when modeling but where do you find this option? I'v looked in Tools/Customise and then had a look in the TechRef manual but I'm still non the wiser. Go to Render Options, select Shaded for Quality and then "Show backfacing polys" will appear as an option. Quote
markw Posted February 4, 2011 Posted February 4, 2011 Just found this thread and I like HomeSlice's idea to have "show back facing ploys/normals" turned to off when modeling but where do you find this option? I'v looked in Tools/Customise and then had a look in the TechRef manual but I'm still non the wiser. Go to Render Options, select Shaded for Quality and then "Show backfacing polys" will appear as an option. Thanks for the replies guys. I've turned it off now. I maybe should have said I'm on a Mac using A:M 15j+. I mention this because under "Render Options" there is no option labeled "Shaded" (See attached screen shots). So I just went through double clicking on all the options. It turns out the prize was behind the "Real-Time" KeeKat! Hope this helps others who might go looking for this particular Off switch. Quote
Fuchur Posted February 4, 2011 Posted February 4, 2011 Just found this thread and I like HomeSlice's idea to have "show back facing ploys/normals" turned to off when modeling but where do you find this option? I'v looked in Tools/Customise and then had a look in the TechRef manual but I'm still non the wiser. Go to Render Options, select Shaded for Quality and then "Show backfacing polys" will appear as an option. Thanks for the replies guys. I've turned it off now. I maybe should have said I'm on a Mac using A:M 15j+. I mention this because under "Render Options" there is no option labeled "Shaded" (See attached screen shots). So I just went through double clicking on all the options. It turns out the prize was behind the "Real-Time" KeeKat! Hope this helps others who might go looking for this particular Off switch. You need to click on "Advanced" to get full control... I highly suggest to use Advanced-Mode instead of Preset-Mode. It is just more adjustable. See you *Fuchur* Quote
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