Flickering rotor shadows

[some1]

I'm watching the livestream right now. The aircraft looks great, but the rotor shadows flickering in the cockpit every odd second are terrible. I know it's a global problem introduced in 1.5, but can't you guys do something about it or work with ED to fix the issue?

[dimitriov]

Doesn't it exist IRL (Honest question) ?

 

Anyway it's up to the graphic engine for this part...

[b00ce]

It looks like the frame rate is causing the rotor shadows to go intermittent. In the real life, its MUCH worse; its like the sun turned into a strobe light and can actually make you sick if it catches you wrong.

[dimitriov]

Ok, I hope then that with a better modeling level, we'll be able to get sick in front of our screen :D

[Cykyrios]

Doesn't it exist IRL (Honest question) ?

As a pilot/passenger in a helicopter, you won't see the flickering shadow because your eyes aren't "fast" enough, while a camera (or video game) can display non-blurred pictures of the shadow, which your eyes can then see, and that is the flickering we notice.

[b00ce]

As a pilot/passenger in a helicopter, you won't see the flickering shadow because your eyes aren't "fast" enough, while a camera (or video game) can display non-blurred pictures of the shadow, which your eyes can then see, and that is the flickering we notice.

I can promise you, I have seen it first hand, the flicker does exist. And it isn't really like you see in videos, you see the whole cabin flicker.

 

Source: 244 hours in the back of an HH60M.:pilotfly:

[some1]

It looks like the frame rate is causing the rotor shadows to go intermittent. In the real life, its MUCH worse; its like the sun turned into a strobe light and can actually make you sick if it catches you wrong.

 

EDIT:

 

somehow I'm still not convinced that it looks like in the simulator...

 

Assuming a 300RPM 3-blade rotor, you get a shadow flicker 15 times per second, that moves through the whole cabin (as you said). In the sim, as it is now, it's more like once per second, or two, you see a static blade shadow in a random place.

Edited April 10, 2016 by some1

[b00ce]

EDIT:

 

somehow I'm still not convinced that it looks like in the simulator...

 

Assuming a 300RPM 3-blade rotor, you get a shadow flicker 15 times per second, that moves through the whole cabin (as you said). In the sim, as it is now, it's more like once per second, or two, you see a static blade shadow in a random place.

You have to factor in little hitches and stutters. The blades are spinning at the correct speed and casting shadows appropriately, so it has to be frame-rate. Even if you're getting 15FPS, you're not going to see the blades flicker properly. Its only going to look like it should once you Get above 60FPS consistently.

 

It looks good enough to me, like I said in my earlier post the whole cabin/cockpit flickers because your eyes aren't fast enough to see individual blades.

[dimitriov]

387 RPM to be accurate ;)

 

A human eye is around 90 FPS. (DOn't really know if it matters). But anyway, shadows already are a problem for most games, they are huge resources eaters... Do you really want it to be calculated and displayed 15 times faster ;) ?

Edited April 10, 2016 by dimitriov

[b00ce]

387 RPM to be accurate ;)

 

A human eye is around 90 FPS. (DOn't really know if it matters). But anyway, shadows already are a problem for most games, they are huge resources eaters... Do you really want it to be calculated and displayed 15 times faster ;) ?

The shadows are calculated in real time anyway; it doesn't matter if the blades are static or spinning at a million RPM, the performance cost is the same. The problem arises when your FPS fluctuates, due to other factors, and it is rendering frames while the shadows are elsewhere due to the timing of frames. This is exaggerated when FPS fluctuates and stutters. :thumbup:

[dimitriov]

A lot to learn I have Master :D

[some1]

The blades are spinning at the correct speed and casting shadows appropriately

 

Except they are not. In DCS, at least in the Gazelle, there is another model of "blurred" rotor disc, that can spin at slower speed. It's needed to make a good looking screenshots, otherwise a still frame would give you a stopped rotor on a screen. But this slower rotor is casting a slower shadow, that flickers with lower frequency.

 

I'm also not sure about shadows being calculated every frame, it depends on the graphics engine implementation.

 

Thus, your theory about FPS fluctuations causing flicker is quite incorrect.

Edited April 11, 2016 by some1

[b00ce]

I'm well aware of the blur model for the rotor; however, it shouldn't spin slower. I would be very surprised if it did and would be forced to consume my head covering. The reason you see the non-blur model more than the blur model is because it is spinning slower and thus has more time on your screen; whereas the blades at full RPM (IE blur model) have maybe one frame in 20 at most.

 

That's not even taking into account that your FPS

and the blades would appear to stand still or spin slower or more erratically.

 

If shadows weren't calculated every frame, you would know, they would be completely broken.

[borchi_2b]

Humans see the world at 50 hertz which is 25 frames per sec. 25 pictures intermiten by 25 none pictures

[some1]

If that were true, 120Hz displays would be useless, yet most people can easily see the difference between 60 and 120Hz, esp. with a fast moving objects on screen.

 

Human eye is a biological device that doesn't work like a mechanical camera and you can't really give a fixed fps ratio for it.

 

Anyway, even if the rotor in DCS spins at the right speed and the shadows are calculated every frame, it's not what a human eye would see in the same conditions in real life.

[dimitriov]

Yes there is a "FPS" limit for the human eye, and it's about 90FPS. This is why, for example, the recommended FPS for the VR systems is 90FPS.

 

Edit : 50 FPS for each eyes, and the brain has to "process" so around 100 FPS. But technically, your brain will artificially "fill" the spaces between each image.

Edited April 11, 2016 by dimitriov

[some1]

I suggest you do some reading on the subject, you can start by following the links provided by wikipedia :)

https://en.wikipedia.org/wiki/Frame_rate#Frame_rate_and_human_vision

 

humans perceive visual flicker artifacts at rates over 500 Hz when a display includes high frequency spatial edges

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4314649/

[b00ce]

Of course the game isn't going to render exactly what the human eye sees, that's nearly impossible. The refresh rate of your eyeball is completely irrelevant to the conversation and has nothing to do with why the rotor blade shadows flicker unexpectedly on screen. That said, as a helicopter aircrew member, I can tell you with 100% certainty, from first hand experience, that you DO see the flicker of the blades in the real life. You can stop beating the dead horse now.

 

As I've said earlier, the problem likely does not lie with any technical problem that may be present in the module or DCS world. Rather that it was the frame-rate of the game/youtube being timed to some extent with the rotor RPM being the culprit.

[firmek]

Except they are not. In DCS, at least in the Gazelle, there is another model of "blurred" rotor disc, that can spin at slower speed. It's needed to make a good looking screenshots, otherwise a still frame would give you a stopped rotor on a screen. But this slower rotor is casting a slower shadow, that flickers with lower frequency.

 

I'm also not sure about shadows being calculated every frame, it depends on the graphics engine implementation.

 

Thus, your theory about FPS fluctuations causing flicker is quite incorrect.

 

This is the point. We can discuss the physics and theory but the fact is that monitors and 3D graphics engines does not naturally reproduce real life effects.

Rotating objects, even extremely fast in 3D programs will not result in the same, blurred effect as in reality or having an impression that the rotation changes it's direction depending on the speed. For this reason 3D developpers and artist use tricks like like blurred textures which replace blade models to simulate high speed rotations. As far as it comes DCS graphics engine seams to not apply such simulation (at least in case of Mi-8, not sure about Gazelle). This is why we can observe sharp, relatively slow moving, flickering blades and shadows.

 

To show the point, instead of rottor blades model:

 

After certain speed, picture like this should replace the 3D blades:

[some1]

I did not start the "human eye fps" topic and I agree, it's not relevant to the discussion here.

 

As I've said earlier, the problem likely does not lie with any technical problem that may be present in the module or DCS world. Rather that it was the frame-rate of the game/youtube being timed to some extent with the rotor RPM being the culprit.

 

You're missing the point.

 

I'm not denying that you can see the flicker in real life, but you said it yourself in this thread, it doesn't look like the one we have in game. In reality the whole cabin flickers (your words) because the shadow constantly and continually moves through the cabin and your field of view.

 

Yesterday I recorded a short, uncompressed movie at 60fps of DCS:Huey and analyzed it frame by frame. The rotational speed main rotor is correct and the rotor is slightly blurred, so that's good. But the shadow is not blurred (it appears as solid as for static rotor) and because of FPS limited to 60 by a typical PC monitor, it just flashes in front of you every few frames at different locations. The blades rotate about 30 degrees every frame, so you get few frames without blade in sight and then, bam, one frame with shadow clearly visible in the cockpit like the rotor has been stopped. This creates an effect that can't be observed in reality by a naked eye, but can be seen on videos of real helicopters because of the limitation of the cameras.

 

As @firmek explained, game developers sometimes have to use "tricks" to simulate the effects that can't be presented in normal circumstances on a computer monitor. So yeah, that's something that DCS developers could fix if they wanted to.

Edited April 12, 2016 by some1

[b00ce]

I understand what you're saying. However, I don't think its a problem and it does not bother me one bit that the rotor blade shadows in the game don't look exactly as my eyes see them in the real life. If you want to get this picky, then the rotor blades look nothing like I see them when I'm flying; they look like how a camera would see the bur. You're looking down a very deep rabbit hole my friend.

[Rangi]

It could be an artefact of you tube compression / frame rates, until we see it in game I wouldn't worry too much about it.

[Mt5_Roie]

So reading through the thread I think I understand the issue. Can you pin point the time on the stream where you see it. In my time of flying the Huey or Gazelle I don't recall every experiencing a flicker effect that would bother me.

[some1]

Sorry for the late response, I missed your question.

 

An example is here:

 

On each frame there's either full rotor shadow, or no shadow at all, so it flickers even at 60 fps.

 

And before somebody says "it's only youtube, in game it will be different", the Huey in game has exactly the same issue. If anything, in game it looks worse because youtube compression blurs the image somewhat.

[Northstar98]

This is the point. We can discuss the physics and theory but the fact is that monitors and 3D graphics engines does not naturally reproduce real life effects.

Rotating objects, even extremely fast in 3D programs will not result in the same, blurred effect as in reality or having an impression that the rotation changes it's direction depending on the speed. For this reason 3D developpers and artist use tricks like like blurred textures which replace blade models to simulate high speed rotations. As far as it comes DCS graphics engine seams to not apply such simulation (at least in case of Mi-8, not sure about Gazelle). This is why we can observe sharp, relatively slow moving, flickering blades and shadows.

 

To show the point, instead of rottor blades model:

 

After certain speed, picture like this should replace the 3D blades:

 

Don't some helicopters have a reduced or negligible effect for that though? I'm thinking of the Mil Mi-24 here, I know the Ka-50 most of the rotor is relatively-ish sharp, only the extremities appear slightly blurred? For me I prefer that, even if it does mean having screenshots with more or less un-blurred rotors.

 

For the Gazelle, when looking outside the rotors seem a little too blurred and flat IMO, though I've only seen videos of it, I'll find out when it's actually released.

Edited April 24, 2016 by Northstar98