Hi/Lo poly Z-fighting during RTT (3ds max)

BARBEERIAN · 07-27-2008, 12:12 PM

I'm having a weird problem rendering out some maps for a model I started. The problem is that basically the renderer is seeing z-fighting between the Hi-poly and Low-poly model during the RTT process. It's mostly happening in places that are flat surfaces on both models. The real weird thing is that it causes Ray miss errors, leaving me with those oh so wonderful red stains all over the maps. Turning off Ray miss check does nothing basically. I just get splotches of BG colour instead of red.

For the record I double checked and 'include working model' isn't checked. Also, I'm using a projection cage on the low-poly (it's enabled too), and it's not cage issues where I accidentally left some cage verts inside the model or something.

Also, I did try throwing a 'Push' modifier onto the hi-poly model which does help reduce the amount of errors but only slightly.

I'm not really understanding why it's doing this. I mean I thought the rays should only hit the hi-poly model and simply correspond to what part of the Low-poly's UV-space it's going to put that information.

Here's a pic of what the render looks like. As you can see it's got ray misses on interior sections of the model in huge patches.

Tiros · 07-27-2008, 12:22 PM

Well, for starters.. this wouldn't prolly solve anything.. but try resetting the x-form.. it's something I always do when I get wierd errors, usually works.. though it should only affect transformations/deformers and normals as far as I'm concerned.. might want to try it anyways though.

And if you're sure the lowpoly cage and highpoly model isn't intersecting.. then.. well, what could it possibly be.. I know I had this error aswell once, never managed to solve it really.. So i'm not quite sure.

Well, I'm sorry mate, but I can't really pin down the error

Cheers

BARBEERIAN · 07-27-2008, 12:34 PM

Quote:

Originally Posted by Tiros

Well, for starters.. this wouldn't prolly solve anything.. but try resetting the x-form.. it's something I always do when I get wierd errors, usually works.. though it should only affect transformations as far as I'm concerned.. might want to try it anyways though.

And if you're sure the lowpoly cage and highpoly model isn't intersecting.. then.. well, what could it possibly be.. I know I had this error aswell once, never managed to solve it really.. So i'm not quite sure.

Well, I'm sorry mate, but I can't really pin down the error

Cheers

Thanks anyway =( Tried resetting the x-form but it didn't work. This thing has me totally stumped. I know I've modelled Hi/Lo poly objects with flat coplanar surfaces and I've never seen this z-fighting type error happen before. Normally the Normals map would just get the blue 'flat' colour, not ray misses.

I even tried making a new scene and merging the hi/lo models from files other than the bonkers RTT file, redoing the projection cage etc.

doylle · 07-27-2008, 12:56 PM

From the image you've shown us, there's only one thing i can think of atm. It looks like you're using your render output as actual rtt output (The padding appears to be 0, typical for render output). This is not at all a correct representation of what your real output is. If this is indeed your render output, just have a look at the real rtt saved files (you can set the dir. somewhere in the rtt menu), it could solve your problem...

BARBEERIAN · 07-27-2008, 01:34 PM

Quote:

Originally Posted by doylle

From the image you've shown us, there's only one thing i can think of atm. It looks like you're using your render output as actual rtt output (The padding appears to be 0, typical for render output). This is not at all a correct representation of what your real output is. If this is indeed your render output, just have a look at the real rtt saved files (you can set the dir. somewhere in the rtt menu), it could solve your problem...

Yes that is the output render. The final files do indeed suffer from the same issue, though they get filled with BG colour instead of red. I posted that pic since it makes it alot easier to see everywhere that it happens.

BARBEERIAN · 07-28-2008, 12:40 PM

Found out two semi-fixes on other forums in case anyone else runs into this problem. They aren't perfect, but it got rid of most of the stuff.

Mini-fix 1: Set the spatial contrast in MR to 0.001 for all four channels (RGBA). (It's under the Renderer tab just underneath sampling settings).

Mini-fix 2: Hid all the geometry of the low-poly object (but didn't hide the object itself) before RTT.

07-27-2008, 12:12 PM	#1 (permalink)
BARBEERIAN Artist 41 - 1	Hi/Lo poly Z-fighting during RTT (3ds max) I'm having a weird problem rendering out some maps for a model I started. The problem is that basically the renderer is seeing z-fighting between the Hi-poly and Low-poly model during the RTT process. It's mostly happening in places that are flat surfaces on both models. The real weird thing is that it causes Ray miss errors, leaving me with those oh so wonderful red stains all over the maps. Turning off Ray miss check does nothing basically. I just get splotches of BG colour instead of red. For the record I double checked and 'include working model' isn't checked. Also, I'm using a projection cage on the low-poly (it's enabled too), and it's not cage issues where I accidentally left some cage verts inside the model or something. Also, I did try throwing a 'Push' modifier onto the hi-poly model which does help reduce the amount of errors but only slightly. I'm not really understanding why it's doing this. I mean I thought the rays should only hit the hi-poly model and simply correspond to what part of the Low-poly's UV-space it's going to put that information. Here's a pic of what the render looks like. As you can see it's got ray misses on interior sections of the model in huge patches. Last edited by BARBEERIAN; 07-27-2008 at 12:16 PM.

07-27-2008, 12:22 PM	#2 (permalink)
Tiros Founder of Statspaddling 1,140 - 152	Well, for starters.. this wouldn't prolly solve anything.. but try resetting the x-form.. it's something I always do when I get wierd errors, usually works.. though it should only affect transformations/deformers and normals as far as I'm concerned.. might want to try it anyways though. And if you're sure the lowpoly cage and highpoly model isn't intersecting.. then.. well, what could it possibly be.. I know I had this error aswell once, never managed to solve it really.. So i'm not quite sure. Well, I'm sorry mate, but I can't really pin down the error Cheers __________________ - My Portfolio \| Sketchbook Thread \| Spec/Normals Tutorial \| STC #23 - Vote now!! - Supporter of good crits

07-27-2008, 12:56 PM	#4 (permalink)
doylle Game-Artist.net Admin 2,199 - 264	From the image you've shown us, there's only one thing i can think of atm. It looks like you're using your render output as actual rtt output (The padding appears to be 0, typical for render output). This is not at all a correct representation of what your real output is. If this is indeed your render output, just have a look at the real rtt saved files (you can set the dir. somewhere in the rtt menu), it could solve your problem... __________________ Jeroenmaton.net - Scetchbook Thread - 3dsMax Viewport Shader - Ten Texturing Tips - Supports good crits -

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07-28-2008, 12:40 PM	#6 (permalink)
BARBEERIAN Artist 41 - 1	Found out two semi-fixes on other forums in case anyone else runs into this problem. They aren't perfect, but it got rid of most of the stuff. Mini-fix 1: Set the spatial contrast in MR to 0.001 for all four channels (RGBA). (It's under the Renderer tab just underneath sampling settings). Mini-fix 2: Hid all the geometry of the low-poly object (but didn't hide the object itself) before RTT.