Flickering shadows on mesh?

[Caelicorn]

Hi guys, 

I'm sorry if someone has already asked this somewhere. I've spent a few days trying to trawl through the forums (and google) for a solution.

For some reason a mesh head I am making shows this gradient like shadow flickering when atmospheric shaders/advanced lighting model is on, and my graphics are set to ultra. I've tried things out on a few different computers, and though the effect is lesser/greater depending on the computer used, I can still see this effect. I've actually noticed it on a few other head meshes I have demo'ed or bought from the MP (or for example, on on some of the mesh bodies I use - where shadows sort of flicker across the mesh in a pixelated fashion).

I have attached a screenshot of the flickering I mean - one is from mesh on the MP, another is from one I have been making. I have also noticed this effect coming from the shadow of a palm tree over my head (and just turning really pixelated on me!)

Can anyone shed any light on why this is happening or how it might be fixed?



Thank you for your time!

[ChinRey]

Although it's unlikely, it may be related to this bug:

http://jira.phoenixviewer.com/browse/FIRE-17290

 

There are several other possibile explanations but the most likely is simply that your graphics card is too busy. You don't mention what hardware you are running but with graphics maxed out and fitted mesh in the picture your computer needs some serious gpu power to cope.

An easy way to check this is to reduce the overall load on your gpu. The biggest factors here are draw distance, LOD factor, textures and fitted mesh. Try to minimize all of those and see if it helps.

[Gaia Clary]

---

ChinRey wrote:

 

You don't mention what hardware you are running but with graphics maxed out and fitted mesh in the picture your computer needs some serious gpu power to cope.

---

Can you explain in more detail why the presence especially of a fitted mesh can give trouble?

 

[ChinRey]

---

Gaia Clary wrote:

Can you explain in more detail why the presence especially of a fitted mesh can give trouble?

---

The simple explanation is: lots of moving triangles and vertices. There is a reason why the system avatar is kept relatively simple and that is that a more complex one would have overloaded any computer back in the early days of Second Life.

Computers today can handle much more of course but fitted mesh attachments can have thousands of polys and your computer has to keep track of each and every one of them. (To be honest I don't know if this is mainly a load on the gpu or the cpu but the two aren't completely independent of each other anyway.)

This explains most of the fitted mesh lag but maybe not all so there might another factor too. Fitted mesh is a fairly recent addition to Second Life and it's really an official version of a "hack" developed by users with no access to the source code. It's very likely it wasn't porrible to implement it as efficiently as features that were built into the SL software right from the start.

[Gaia Clary]

---

ChinRey wrote:

Computers today can handle much more of course but fitted mesh attachments can have thousands of polys and your computer has to keep track of each and every one of them.

---

Hi, ChinRey

Thanks for the very detailed explanation. However, after thinking a bit about your argument doesn't this apply equally to Fitted Mesh and Not Fitted Mesh?I mean even when you create a regular attachment without using the Collision Volumes for Fitted Mesh, those regular attachments can also have thousands of triangles...

Or is there anything with Fitted Mesh that makes its impact on the computer different from the impact of Not Fitted Mesh?

[ChinRey]

This is a bit off topic of course, I just mentioned fitted mesh as one of several factors that add significantly to the render load. And also, my explanation is a bit simplified to put it mildly but...

---

Gaia Clary wrote:

Or is there anything with

Fitted Mesh

that makes its impact on the computer different from the impact of

Not Fitted Mesh

?

---

Two, three or four reasons - I can't say for sure if the first two are significant.

1. How the feature is implemented in the software. Regular mesh was developed in 2010 by Linden Lab themselves and officially launched in 2011 after extensive testing. Fitted mesh was introduced quite a bit later at a time the software must have become even more cluttered nad harder to upgrade efiiciently and, as I said already,  mostly developed by people who didn't have access to the software itself nor the resources to do work required to optimize its performance.

2. Triangle size. When we talk about high poly regualr mesh, it's usually silliness like highly detailed shoelaces and such, lots and lots of very small triangles. These add quite a bit to the download weight but since they're too small to be actually rendered (unless you zoom in very closely on them), they're culled out long before they reach the gpu so they don't add anything to the render load - or the actual look.

3. Volume. When was the last time you saw an avatar covered from head to toe with three or more layers of high poly regular mesh?

But most of all:

4. Flexibility. A regular mesh moves as a single rigid unit, the distance between the vertices remain the same and the shape and size of the polys remain the same. Not so with fitted mesh. Each vertice moves individually (although not independently) and the triangles between them have to stretch and compress in various directions to match. I think it's fairly easy to see that that makes the calculations a lot harder for the poor gpu. Back when LL developed the formula for calculating render weight, Nyx Linden did some throrough testing of flexprims. The result he got was that they are twice as hard to render as regular prims. You can't compare directly with fitted mesh of course - flexiprims are path absed while fitted mesh is skeleton based - but the basics is the same: flexible objects are much harder to render than rigid ones.

[Caelicorn]

Hi Chin, thank you for the response! And please go off topic you two, as much as you like, I'm happy to try to absorb and learn what I can and if it doesn't make sense to me now I hope one day it will.

As for hardware, the 'best' system I tested it on was this one, which is pretty old now:

i7 Sandy Bridge Processor 3.4GHz
Sapphire ATI Radeon HD6970 2GB GDDR5 Graphics card
6GB RAM

All three computers are about on par though. I did also test in the standard viewer only, not Firestorm etc... So while I was wondering if it was related to diffuse texture in alpha blending mode (because my mesh certainly is using this technique), it's not in Firestorm? Could this still be the issue? I also checked to see whether or not my mesh was simply too complex and tried a simplified version, and it did -seem- at first to help, but then I noticed the flickering effect had just moved to different points on the head >.<

I haven't actually checked if the head from the MP (in the first picture I showed you) used multiple textures or this diffuse in alpha blending mode, but I will have a look when I log in today. I don't want to name names as its a popular product, but I'd be happy to point anyone to the demo if they want to bring it up in their game and see if it does the same thing? But yes... it just seems more likely the problem is my end! Grrr!

When I log in today I will play with settings as per Chin's suggestion, and see if they alleviate the situation.

Thank you for your responses and your discussion. I love the feeling of something I am trying to get a grasp on going over my head - it means there is so much more to explore and learn!

 

 

[ChinRey]

---

Caelicorn wrote:

 

i7 Sandy Bridge Processor 3.4GHz

Sapphire ATI Radeon HD6970 2GB GDDR5 Graphics card

6GB RAM

---

That should be enough. I'm on a slightly weaker computer right now running ultra graphics in a not too laggy but not exactly low lag location and can't see any such problems.

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Caelicorn wrote:

I haven't actually checked if the head from the MP (in the first picture I showed you) used multiple textures

---

It's not a single item's texture that can cause lag, it's the total number of textures in the scene.

But I think we can safely rule out general gpu overload as the cause here anyway.

 

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Caelicorn wrote:

it's not in Firestorm? Could this still be the issue?

---

As fas as I know it's only Firestorm. I use four different viewers reguarly and never seen that flicker in any of the others, nor have I heard of anybody who has.

[arton Rotaru]

I think you are simply asking for too much from a real time renderer. And especially trees are prone to give rather poor shadow quality.

The solution is, do not zoom in that close on your nose. Or get out of the shadows and step into the light. :matte-motes-tongue:

[ChinRey]

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arton Rotaru wrote:

I think you are simply asking for too much from a real time renderer.

---

That was the essence of my first reply of course - although I tried to be a little bit less blunt.

But when I wrote my second reply to Caelicorn, I was logged on with a computer with very similar specs, same viewer, graphics set to ultra. The environment was fairly low lag but both I and a friend standing next to me were wearing mesh bodies, mesh hands and feet, and mesh clothing. I was not able to reproduce the problem in that setting. Not too long ago I did a serious load test with that same equipment, I went to Skinny Dip Inn with graphics maxed out. That was lag Hell of course but I never saw anything like this and I'm sure I would have noticed.

You answer is very, very good general advice, arton. I wish everybody in SL would read it and take heed. But this particular case seems to have some other cause than general render overload.

 

Edit: This is a shot i the dark and may not even help if it hits the mark, but did you check frame rate, Caelicorn?

 

Edit 2: With all that being said, I'm not very familiar with mesh heads and for all I know, that may be the factor that drives the render load over the limit. According to people I've talked to who are involved in Project Bento, that project's main purpose is to offer a less render heavy alternative to all those different mesh bodies and pieces and especially the new breed of animated mesh heads. Now a Bento avatar is so render heavy there was serious doubt they could make it at all and it comes with a crash warning for older computers. What does that say about the functions it is supposed to replace? Only Linden Lab can answer that and they won't - they're even less blunt about it than me.

[arton Rotaru]

Idk, my experience with shadows always has been that they are rather poor and pixalated at the edges. Even More so with SSAO off. There are several Debug Settings in the viewer indeed, to soften the shadows and whatnot. Third party viewers may have tweaked those settings, and/or have them exposed in their GUI. But since these are individual settings, you can't control how other people may render them anyway.

[Whirly Fizzle]

Shadows can sometimes flicker badly if Object-Object occlusion is enabled - though this is usually seen on Mac systems.

Activate the Develop menu in the top menu bar with CTRL+ALT+Q.

Develop -> Rendering -> Object-Object Occlusion -> Untick it.

Does that help at all?  If not, probably better to enable O-O Occlusion again as it can cause a performance hit when disabled.

[Whirly Fizzle]

Possibly also related to your problem: https://jira.secondlife.com/browse/BUG-6583

[Caelicorn]

Hi guys, thank you again for all the input! I just had a look and Im currently on 16.5 FPS while Im seeing the issue... I'm not sure if that helps to identify it or not...

Whirly, I just tried unticking the OOC but it didn't work, however I disabled sun+moon projectors and it was completely fine, so the problem is definitely with the shadows

Arton, if it is indeed a problem with my computer(s) - which is actually what I am starting to think now (it's all very confusing), I'm actually heartened in the fact that I can most likely do what I do, ignore the weirdness, and just hopefully get some people on other computers to come and look at my stuff from time to time to tell me if its borked! Basically my main concern here wasn't my system, but that I was worried I was making some sort of broken mesh, and if I ever entertain putting it on the MP, I'd had to put something munted up there.

But as far as this situation goes, I'm thinking if people don't see the same issue with the head as I do, it's probably ok?

 

[arton Rotaru]

I wasn't referring to your computer, rather the real time render engine second Life actually is. To be honest, I can't tell whats going on, judging from your pics. They are kinda small, and probably a video showing the issue could help seeing whats going on more clearly.

I just wanted to say, that shadows can look very pixelated at the edges. Especially from trees. But if you see this ONLY happening on certain objects, it may well be something else is going on.

[Whirly Fizzle]

Can you make a video showing the effect?  That would help a lot.

Even a quick gyazo gif would help.

[Caelicorn]

Hi guys, yes I have frapsed it and put it on youtube for you to look at. I hope you can help me figure it out >.< Just today I had my friend (you can see her sitting in the chair) see if she saw a similar problem on ultra (with another head I am also working on), and she screenshotted for me the same effect I have been seeing. I'm not sure what her computer stats are though, but she also plays a lot of new games so I'm assuming it's decent.

 

https://www.youtube.com/watch?v=JTgsvF__Iy8&feature=youtu.be

 

If you look at the nape of the neck around the start of the vid you can see what I mean, though I was trying to catch it when it was more pronounced, sometimes I see huge ribbons of this effect along the neck, especially on the second model I am doing. When I turn the head around you can see the distortion I am meaning on the temple and around the nose.

If you would like to see if you can see this effect in game, I can message/note you with the demo of the mesh head I have found on the market place which does the same thing? It might help me to see if you can see the same effect on the neck?

 

Otherwise I think Ive determined this is not the shadow flickering we've mentioned here. I was looking at my friends maitreya body and my niramyth one (I also have a slink one which isn't so pronounced), and the shadows sort of flickering as they creep about seems to be a different issue. This one looks like roaming pixelation???

Thank you again for your time >.< I hope we can figure it out!

[Whirly Fizzle]

Hmmm that wobbly effect is normal. You'll even see that on the default avatar mesh & shadows cast on objects.

You can lessen the effect by tweaking the shadow settings.

Im using Firestorm for these images but the effect is just same on the LL viewer.

My avatar is wearing no mesh on its upper body here. Sun is set to midday. The shadow in the chest is cast by the avatar head.

Close up image showing graphics settings. Shadow and ambient occlusion settings are at defaults.



 
Here is a gif showing how flickery the shadow is when moving camera.

https://i.gyazo.com/ee9da0e66f5b17d41ac01735944b90fb.gif

If I make these changes to shadow settings it mostly eliminates the problem:



Here's a gif showing the shadows with the above settings while moving the camera:

https://i.gyazo.com/dc4d9dc031c531d0de1c184c786593ee.gif

Cranking the shadows or AO settings up like this do have a performance penalty.

Curious if you remove the hair from the mesh head shown on your video if the flickery shadow near the eye goes away?

Is there a transparent mesh layer in that area which could be making the effect worse in that area?

Possibly a problem with inverted normals in the areas that flicker badly on that head?

[Caelicorn]

Oh man it's shameful if the problem was a standard SL issue with such an easily solution, but I'll have a look at it when I log in next and let you know (but hey, I am a SL noob so I'm happy to learn about this). I hope it does fix things up, I'm super hopeful after seeing the difference demonstrated in your post, and I will have more of a play with the settings.

Because there aren't transparent mesh near the head and no inverted normals either (I did check for this), I'm hoping that the answer is as simple as what you've defined! I actually haven't seen some of the settings you have open in your ss, but I do have FS so first I will try to replicate what you have there, then have a play for myself.

I'm sorry if it's frustrating for you guys to deal with so many silly questions sometimes, but it is highly appreciated! 

[Whirly Fizzle]

Not frustrating at all so don't worry 

Those extra exposed settings for shadows & Ambient occlusion you will find under World -> Photo & Video -> Phototools on Firestorm.

Word of warning though - some of those exposed settings are "dangerous" in that they will crucify your performance if you push them too high for your system.

Be especially careful with the Shadow Resolution (Shd. Res) setting. If your system can handle it, you can crank it up BUT if you try to take a very large sized snapshot with Shadow Resolution above 2.0, you have a good chance of crashing the graphics driver, even on a Titan card or a GTX 980.

The D button next to all those settings will reset to default.

You may find this tutorial helpful for learning what all these shadow & Ambient Occlusion settings do in Phototools: