Why does VR require a Video Card?

bobbo123

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I'm planning my next build to be VR capable...so I have all the recommended specs. I've read several articles that make the point that if a system can handle 4K UHD at 60mhz then it almost certainly will handle VR....because 4K processes more pixels per second than does VR including its subfields and all that goes with it.

Well.......looking at the specs most Gen 6 Intel capable motherboards/cpu's that typically inlcude HDMI 1.4 all say they can handle 4K UHD at 60mhz. So....WHY is an additional video card required at all?

Now...I can see that such a bare system might totally max out the cpu so that multi-tasking is not possible....but what else can you "do" when in Virtual Reality? (Forget background encoding...that can be done later?).

So Again---my simple read says with the right motherboard and cpu===you don't need any video card at all. I do assume I'm wrong. What am I missing?

Also...it rather irks me it is about impossible to find out if when buying a video card whether or not the motherboard video connections will still work or be disabled. I have to assume the general rule is that on-board connections are disabled on detection of a video card? That has been my experience so far.
 

KalTorak

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bobbo123.

This is actually a very complex problem. But simply put,

CPU graphics is for advanced 2D applications or light 3D applications. This might require say 497Million calculations to maintain 60Hz at 4K.

The New 1080 released by Nvidia is able to perform 9Trillion Calculations. That is 18108X greater. Hopefully you see the problem.

The reason for this is depth. It needs to work out what the order of the scene you are looking at is. Otherwise you could see through a houses walls, you could see caverns underground, people would be invisible etc etc.

If you want to really get into it, take a Computing degree, its not something to learn from a forum :)
 

bobbo123

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Thanks rgd: You have repeated the very basis of my question: WHY? The 4K UHD at 60mhz throws up more pixels per second than required by VR headsets. So ............ WHY.......... the additional stated requirement of the Video Card?

What additional function is the video card providing? I want to know why....not just follow a system spec without knowing why.
 

Tri23

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So, this is how I understand it.
Onboard graphics cards are meant just to be able to display a 2-dimensional desktop. It is meant to display excel spreadsheets, 2-d images, text.

3-dimensional graphics take much more computing power. Hence why the need for off-board graphics card became a market for gaming.

So, what does the video card do? It allows you to render complex graphics REALLY fast. You may be able to play a 3-d game on your on-board graphics, but it will not refresh the screen as fast.

Why does this matter with VR?
Because think of your Headset as really (2) monitors, and those screens need to refresh at atleast frames/second so you don't feel nauseous when you turn your head. The less choppy the image looks, the less you will want to throw up.

That is why. :)

The deeper "why" gets down to system architecture and processor math. (floating point.. yadda yadda.)
Pretty much, onboard graphics is meant to show "excel".
A mid-level graphics card is to let you play the Witcher 3 and look really pretty.
A high level graphics card makes Witcher3 look OFF THE CHAIN, and allows you to play VR where your eyes each get their own monitor.

Oh yeah! Graphic cards also do all the math for physics and other cool stuff. (it gets deep!)
 

Tri23

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(hope that answers the question)
Re-reading the question of the 4k display, I think the answer comes down to rendering 3-d images and physics in real time.
 

bobbo123

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Thanks tri. Here is what VR has to do minimum spec: • 457 million pixels/second: Rift/Vive @ 90Hz

Here is what a 4K Monitor at 60 Hz refresh puts out: • 498 million pixels/second or about 8% over minimum specs.

Now....to me its just about number of pixels and has nothing to do with 3D rendering as that is nothing but pixels? What does physics in real time mean other than throwing up pixels per second?

So...specs should be specs? As in: for VR you need a system that will produce a minimum of 457 pixels per second. HOW you reach that number should allow for all video card or all cpu or one video card or two video cards?

One "issue" I see is that videos cards and their specs with the cpu were developed to play games as the maximum demand application.....but behind the scenes.....4K UHD was developed on CPU's alone with even higher demands. Its a "stuck in marketing" routine that I suspect is in play here.....but I don't know....and I still assume I'm wrong otherwise once you list a 6th Gen I-7 CPU that can display 457 Pixels/Sec you would be over with the video card only if you want to surf the web while a friend plays Doom?

Something still needs to be explained, otherwise....I can see myself buying the MB and CPU first and seeing how that works out? IOW--what is the spec that the CPU/MB/RAM can't handle all on their own?
 

Tri23

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>> Now....to me its just about number of pixels and has nothing to do with 3D rendering as that is nothing but pixels? What does physics in real time mean other than throwing up pixels per second?

It is the math involved to render a 3-d object, and have that object interact with the rest of the 3-d world. Pixels is just how good it looks on the screen.

Example: "You throw a ball against a wall. Where does the ball land?"
That is all based on,
- What is the ball made of, and how does it react?
- What is the wall made of, and how does it react?
- How hard was the ball thrown?
- What is the resistance of the ball against all acting surfaces?

Pretty much some deep newtonian physics. Then you take in the "holy grail" of 3d objects, Water. If you pour a cup of water onto a table, what happens, and how well can you re-create that in a 3-d world? It is problems like this that you purchase a high-end graphics card.

(gonna nerd out a little)
Going beyond just gaming applications, there are labs out there which are nothing but high-end graphics cards all linked together to solve problems like this. Aero-space, exploratory drilling, particle physics. Graphics cards are just REALLY good at creating simulations SOO much faster than a CPU. (see CUDA).

My main point, is it looks like you are stuck the number of pixels is the sole factor, when really it comes down to the overall performance of the card in the environment you are using it. Kinda like # of horse power does not mean you are gonna win the race.

---

There are more questions, but I think I answered the key one? (maybe not.) :p
 

Tri23

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(thinking about it)
If your decision is, "Can I get by just running all the graphics off the CPU and onboard graphics", there is an easy solution...

Build your PC and do not purchase the graphics card. Then try running VR and see how it performs. If an I7 can handle it alone, then great! You will be able to run the software and hardware, but what you should encounter is a poor refresh rate.

If that occurs, then go out and purchase a graphics card. If you are happy with the performance, then you are set. :)
 

bobbo123

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Tri---I think you are on to the key. I AM just thinking pixels. And with a tv..all the pixels are in the broadcast and they just have to be "thrown up on the screen." YOU are right....in VR the nearly the same pixels have to be....... CALCULATED. That involves about the same computing power to "present" the pixels, but in VR it requires a whole bunch more ..."floating decimal point calculations" to actually create the picture BEFORE it is thrown.

I/We could both be wrong, but I think that is it.....or for me, close enough and logical enough that I'll be buying the Video Card at the same time.

Thanks for hanging in there with me. I feel good.
 

bobbo123

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Actually....I'm kind more interested in World Travel....like using google maps to fly over different areas of the world....or museum trips, or backbacking without the flies.....

.......and then even more about augmented reality.

Games have never maintained my interest. Fun until that one moat I can never get over kind of thing.
 

bobbo123

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BTW--I can't find any button to mark your post as Problem Solved. You did...so thanks again.

I think rgd was on to it as well, but I needed more words.
 

KalTorak

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bobbo123.

This is actually a very complex problem. But simply put,

CPU graphics is for advanced 2D applications or light 3D applications. This might require say 497Million calculations to maintain 60Hz at 4K.

The New 1080 released by Nvidia is able to perform 9Trillion Calculations. That is 18108X greater. Hopefully you see the problem.

The reason for this is depth. It needs to work out what the order of the scene you are looking at is. Otherwise you could see through a houses walls, you could see caverns underground, people would be invisible etc etc.

If you want to really get into it, take a Computing degree, its not something to learn from a forum :)
 
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