3d models glitching when camera moves

I have an issue where as the camera moves, one of the 3d models in my scene does not display correctly.  As the camera moves different parts of the model turn black on a frame by frame basis and on some frames the entire model is black and on others it displays correctly.  In trying to narrow down the issue I have found that this only happens when there is any light other than ambient in the scene.  The other observation I have made is that when I turn off another model in the scene, the problem goes away even though the two models do not interact directly with each other.  The glitchy model is a table (inside a 3d model house) and the geometry is very simple and is not using any proprietary modifiers.  The model that seems to be affecting it is the grass lawn (outside the house) and although it is more complex by nature, I made it myself and it is as basic as it can possibly be.

Any ideas on what might resolve this issue would be most welcome!

Ken 

 

Comments

  • UPDATE-

    I moved the grass back in Z space and the problem only occurs when the camera reaches the point in Z space where the grass begins.

    Ken

  • Hi @TTSProd on your timeline, right click the scene camera and open it's properties, set the near clip distance to around 1.00 and the problem should be solved :)  

  • Thanks @NXVisualStudio !

    I had no idea that setting was there.  It was set to 1.00 already, but I can see playing around with it does have an effect on my issue!

     

  • edited October 2016

    Glad you have it sorted now @TTSProd, I'm guessing you're using HF4P? :) 

  • NXVisualStudio

    Yes, I am using HF4P.

    As I was messing around with this I got curious about what exactly the camera properties clipping adjustment is doing.  I checked the User Guide but could find no mention of it.  Any idea what the process behind this control is?  My problem is pretty much solved, although I could not find a perfect setting that fixed it for the whole camera move, I managed to hide what I couldn't fix.  My near clip distance is now set at 10 and I wonder if that could cause unforeseen problems.  Do you know what it's doing?  

  • Triem23Triem23 Moderator

    Near Clip Distance is telling the camera how close a 3D object can get to the camera before the camera can no longer see it. With a Clip Distance of 10, anything closer than 10 pixels to the camera is no longer rendered.

    3D models are tricky tricky things. Hitfilm supports OBJ, LWO and 3DS models, but the kicker is that it supports the BASE SPECIFICATIONS for the model type. What does this mean? Well, if you get a 3DS model that was textured in V-Ray, it's probably not going to import into Hitfilm correctly, since V-Ray is a proprietary, 3'rd party plug-in renderer that supports all kinds of things that the base 3DS model doesn't (and before the thought crosses your mind, adding V-Ray or Mental Ray or any other third pary render support has a variable amount of coding involved, but also involves licensing fees. How much does Chaos Group--makers of V-ray--want as a license fee for Hitfilm to read it's $1000 software format? Answer, enough to really raise Hitfilm's price a lot)

    Additionally, a lot of the free models on sites like Turbosquid are, to put it bluntly, terrible. Texture mapping might be screwed up, geometry might be unoptimized--geometry might be built stupidly to begin with! With 3D models (This is going to delve a little bit into the technical area. Just a dip of the toe.) one thing you don't want to do is hang too many poly edges on a single vertex--something often done in free models. One would want to avoid very long, thin polys, which can cause flickering. A model might have incorrect normals (picture a table. Now add a pencil in the center, eraser down against the table, point sticking straight up from the table. The table represents the poly. The pencil is the "normal," which is an imaginary line perpendicular to the face of the poly. The normal is what the camera uses to determine if a poly is visible to the camera and it's angle to a light source)... i have several free models where half the model is "inside out..." The modeller set "bidirectional normal rendering" is his/her software, but that's not part of the bas model spec, so hitfilm doesn't do that--therefore, half the model is "backwards" from the camera.

    So there's a lot going on with 3D models.

  • @TTSProd Everything @Triem23 has said above is spot on and we cannot stress enough how important it is to be cautious before purchasing models, 

    If you see that a model is only compatible with Vray Vx.xx (Version) then this indicates that a good portion will be using channels only supported by Vray and it's unique properties, so if you do buy a model that depends on Vray then you will need to strip back all the implementations involving the renderer and re assign the normal base materials provided by your software, it's a pain but by the end of it you will have a fully working model.

    On the subject as to why HitFilm flickers geometry, this is down to the Z-Buffer and what it's referred to is Z-fighting or stitching, this is when a primitive or multiple primitives share the same value in the Z-Buffer, so you have coplanar points/polygons that are in the same position or share the same space, if the precision of the Z- Buffer is too little then you will have one of those polygons winning, a frame later and another polygon wins and the process repeats causing this flickering,

    As to why changing the Near clip distance has the (fix)
    I'll try to explain this in short - the zNear (near clip distance) clipping plane value is too close to 0.0 and this hits the depth buffer precision dramatically again in short the equation hits infinity the further away you are, so by changing the near clip distance to a value greater than 0.10 sorts the tradeoff between range and precision. 

    This was a fix released in HF4P (update 3) also maybe the buffers depth resolution was increased. :) 


  • Triem23Triem23 Moderator

    And to even further expand on @NxVisualStudio expanding on what I wrote, with co-planar or co-terminal geometry (which is sloppy modelling) or reversed normals, all of that can be fixed, but it requires knowledge of the 3D software equal to just having made your own model to begin with. Although I assume for a skilled modeler fixing issues takes less time than scratch builds. 

  • NXVisualStudioTriem23 !  That was invaluable information.  I think that there should be a section in the user guide dedicated to guidance on the use of 3d models in Hitfilm.

    I learned my lesson after buying one 3d model and it being useless in Hitfilm.  As 3d models do not have any form of DRM built in, the sellers have a strict no refund policy and because Hitfilm is more of an indie platform, nobody I have found sells 3d models that are certified for Hitfilm.  I understand that FXhome can't keep the price of the software reasonable if they have to pay for licencing fees.  Maybe more work could be done on making Hitfilm deal with free (terrible) 3d models better.  Like more advanced options on import to deal with inverted normals, geometry issues and Z-fighting if thats even possible.  Another idea is working with turbosquid or another 3d model seller to include Hitfilm compatibility recommendations.  Hitfilm is a great program for the price and that's why I'm using it, but it has also at times been the source of enormous frustration when it comes to compositing with 3d models and there must be some cost effective way to make it easier for people to use the software as it is intended to be used.

    All that being said, I use free models exclusively or just make simple ones myself because paying for them is too risky and I've gotten better at fixing models by replacing V-ray and/or Mental Ray materials with standard materials and getting rid of proprietary modifiers that Hitfilm can't interpret.  Thanks to this thread I've learned even more and will now look into "too many poly edges on a single vertex" and see if that is an issue causing some of the problems I still have and also to try to find a way to "increase precision in the Z-buffer" to get fix the shimmering. 

    Here is an example from a scene I'm working on (still a work in progress) that has issues I'm trying to rectify.  There is a lot of shimmering going on and the interior lights don't cast on the ceilings correctly through the sheer curtains as the camera moves towards the house, seen as a dark line moving along the ceiling in sync with the camera.  I believe the light casting through transparent models is a bug, but I welcome any ideas you guys might have.  Thanks again for the informative reply's!

    https://youtu.be/XSdkokmwT1Q

  • @TTSProd That's cool :) also what is your antialiasing set to ? this to me looks like lines and edges pixelating.    

  • NXVisualStudio antialiasing is set to 4xMSAA.  I'll bump it up to max (32x MSAA) and see if it helps!

  • NXVisualStudio The render just finished and I'm hard pressed to see any improvement or even difference between 4x and 32x...  Except in the time taken to render.

  • Triem23Triem23 Moderator

    TTS I will note that I've "returned" models to Turbosquid a couple of times. I was able to explain the compatibility issues and get a refund, but I had done this less than 24 hours after purchase. I guess it also depends on the individual seller not being a jerk? 

    I do note @NxVisualStudio created a "Celestial Model Pack" optimized for Hitfilm (Tony, paste your own download link) and is partway through building a City Pack that's already shaping up nicely.

    Hitfilm has improved it's handling of geometry over the last couple of versions. 4 Pro in particular adds improved Z-buffers (less "shimmer"), and the Cook/Torrance shader lets one get looks from Hitfilm 4 that were impossible in Hitfilm 2 and 3. 

    But, yeah, sometimes free models are a pain. 

  • A note on 3D models.  Funky rendering with inaccurate geometry is not just a HF thing.   Its a problem no matter what you use to render.  I have run into this problem with every 3D package I have ever used. (And, back in the day,  I wrote .obj files in the original format on Wavefront).

    Bad geometry is bad geometry.  And it will fritz out no matter the rendering code.   There have been times that I just had to rebuild the object in the native 3D software I was using at the time.  It sucks, but that's the reality.  

    Another thing that creeps in are co-planar polys.   These are duplicates that lie one on top of one another.   That makes things blink every time.

    Also, many of the objects you see online, were translated from other formats.  This induces errors in the points and polys that make up the object (such as co-planars).  Imagine the problems that crop up  from switching back and forth between triangulated geometry to 4 point polys and back again.  Not pretty.

  • edited October 2016

    ...I just typed 2 responses because the first did not post immediately and I thought something went wrong.  It turns out posts have to be approved now and that's why the first didn't post immediately.  So, sorry for the redundant replies.

    EDIT:  Argghh! This one did post immediately!  What's going on??

    So, again sorry for the redundant replies, once they are approved and are posted.

  • Triem23Stargazer54

    I typed out detailed responses but the forum held them for approval and that was 2 days ago so I assume they have been denied.  I seem to be able to make short posts so I'll just say thanks for the information.  I sure wish I knew why my posts suddenly need approval though...

    Ken

  • @TTSProd In general, you should never see that message saying that your posts need approval. It must be the spam filter that is being over zealous. Calling the great @DanielGWood to tame the beast :)

  • Triem23 I also tried to return the model I purchased that did not import into Hitfilm properly to Turbosquid and my request was refused even though it was also less than 24 hours post purchase.  I'm glad it worked out for you, but those were exceptions.  It makes working with hitfilm frustrating at times because there is no reliable solution.  Use free models of questionable quality and they probably won't work well, use higher quality paid models and they still possibly won't work well and you will be out the money you paid for them.  Perhaps FXhome should start producing models for Hitfilm and sell them on the site!  As it stands acquiring 3d assets for use in Hitfilm is difficult to say the least.  I have seen @NxVisualStudio 's celestial model pack, it looks great and I applaud his efforts!  Unfortunately it does not fit thematically with my current project.  I am also looking forward to the city pack as well!  I agree Hitfilm has improved the handling of 3d models since I first started using it (Hitfilm 2 Ultimate) but it still suffers from a lack of compatible assets.

    Stargazer54  At this point I am using three pieces of software and the results in each are different when importing the same model, sometimes better, sometimes worse so I see your point.  I've had the most success downloading free .max files, removing proprietary renderers and some modifiers (some modifiers do translate properly like UVW Map) and exporting to .obj.  Then import to Hitfilm and check it. If there are problems I go back to 3ds Max and try and fix the issues I saw in Hitfim.  Sometimes I can make them acceptable, sometimes it's impossible at my skill level as it would take rebuilding the model or major sections of it and I'm just not there yet.  Although I'm learning a lot and can now get more models to look acceptable in Hitfilm, I still wish there was a source for models that were certified to work in Hitfilm.

  • edited March 2017

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