Graphics for the Uninitiated

[Dyno]

Hi!

I am new to 3D graphics and have learned a lot from this website, particularly its glossary and a couple of reviews. I was wondering if I could get some help from the experts here on a little project.

I would appreciate someone writing a paragraph for the novice or laymen on what graphics are and why a video card is necessary to create them. This is for a news letter so it needs to be general and fairly brief, yet informative on a basic level.

Any assistance would be appreciated.

 

[digitalwanderer]

You sure this isn't a homework assignment? :|

 

[Dyno]

HAHA! I haven't done homework for 15 years. I just don't want to steer co-workers wrong or come off as an idiot regarding this topic.

 

[nelg]

http://www.pcpro.co.uk/custompc/features/71102/3d-perspective.html
Deano Calvers article is a good start.

 

[Dyno]

Thanks for the article! That gives me quite a bit to chew on. Now I just have to boil those 10 pages down to around 150 words.

 

[ShootMyMonkey]

This is about as succinct as I can put it --

Computer graphics is essentially the process of taking some data that represents and describes "things" and then creating an image of these "things" using that representation. About the only purpose video cards had in the beginning was simply control logic for the displays. In other words, making sure your video card refreshes every so often, making sure it scans properly at the correct rate and resolution, making sure a pixel in the image produced the correct pixel on the screen, etc. This isn't really complicated stuff per se, it's just that it's a lot of tedious housekeeping, and software developers typically have better things to worry about. When 3d accelerators came around, their sole purpose was to draw triangles, and draw them fast. We make up the representations of our "things" using triangles simply because the geometric properties are fairly simple and convenient. They don't work for everything, but nobody cares about that in the hardware world. Simply put, we need video cards because they are specialized to go from "representations of many many small parts of things" to "image of things" very fast. In turn, the GPU added on extra features to the 3d accelerator chips that enabled them to not only draw, but also do some part of the math to take an extra workload off the CPU.

Of course, because they're so specialized, it also means that they can give us some headaches should we choose to do something that's not so ordinary. That's why people started the whole business of making shaders and being able to alter the programming of the GPU. And even now, that means little to a whole software package, but... small steps.

 

[Dyno]

Thanks ShootMyMonkey, that helped me understand a bit more of the theory.

One thing I am confused about. Refresh rates. I know that this is measured in 'Mhz' but how do they relate to refresh rates per second. Is it one to one? For example, if a graphics engine is running a particular program on a screen size at 75Mhz is that 75 times per second.

I also heard that less than 75 frames per second has a noticable 'flicker' effect when viewed, is this the refresh threshhold for believable 3D graphics?

 

[Captain Chickenpants]

Thanks ShootMyMonkey, that helped me understand a bit more of the theory.

One thing I am confused about. Refresh rates. I know that this is measured in 'Mhz' but how do they relate to refresh rates per second. Is it one to one? For example, if a graphics engine is running a particular program on a screen size at 75Mhz is that 75 times per second.

I also heard that less than 75 frames per second has a noticable 'flicker' effect when viewed, is this the refresh threshhold for believable 3D graphics?

Refresh rate is measured in Hz which means cycles per second. I.e. a refresh rate of 90Hz means that the screen is updated 90 times per second. Their is not necesarily a 1:1 mapping between refresh rate and frame rate. The refresh rate is a part of the display mode chosen and is completly independant of any 3d that may be going on. The frame rate is controlled by the 3d application. The application can choose to lock the framerate to only swap to a new rendering surface on a VSync (the point when the monitor is not actually drawing anything but is going back to the start of the screen to start displaying again), this is generally done to avoid 'tearing' where the screen is halfway through displaying something when the render surface changes so you end up with half of the display for one frame and half for another.

The 75Hz flicker you mention is basically that your eyes can perceive that the screen is not a solid image but a series images drawn at 75Hz, it is nothing to do with 3d but is simply a factor of the response of the phosphors used in CRT's and the sensitivity of the human eye.

CC

 

[Dyno]

Thanks for the correction, Cpt!

 

[digitalwanderer]

And just to answer your next question, there is no set "minimum framerate" where people percieve flicker...it varies from individual to individual and from game to game.

For monitor refresh rates you want to set it as high as your monitor supports it. I like 100Hz but can handle 85Hz, 75Hz is pushing it a bit and 60Hz literally gives me headaches after only a few minutes.

 

[silence]

And just to answer your next question, there is no set "minimum framerate" where people percieve flicker...it varies from individual to individual and from game to game.

For monitor refresh rates you want to set it as high as your monitor supports it. I like 100Hz but can handle 85Hz, 75Hz is pushing it a bit and 60Hz literally gives me headaches after only a few minutes.

i can do 75, but i notice flicker if there is lots of white or bright....

thats why my next monitor is this :

19 inch IIYAMAVision Master Pro 454v
Max Resolution :1920 x 1440 @85 Hz
Max Refresh rate :103 Hz at 1600 x 1200

IMO, thats the best 19'' there is.....

 

[Dyno]

Alright, this is what I have as a first draft. It's pretty basic because it was suggested I don't go into much detail. This is the relevant segment. Tell me what you think and you can be brutal.

__________________________________

3D graphics must not only look realistic but they must move convincingly and maintain their visual integrity when they are circumnavigated by the player. Furthermore all of this must happen continuously to the tune of several dozen times per second if they are to be presented consistently enough to fool the human eye. These demanding operations are quite simply not possible without the introduction of a 3D video card (also called a 3D graphics accelerator) to your computer system.

A 3D graphics accelerator draws simple shapes (polygons) and places them at points in 3D space for your viewing pleasure. These shapes are put together to create the objects you see on your screen. The card also gives colour, texture, and reflectivity to these objects so that light plays off them in a natural looking way. This is not a one-time process. Each fraction of a second this procedure is repeated in co-operation with mathematical computations that insure the object responds in relation to you, that its depth and detail remains consistent. The end result is a virtual 3D object that displays all of the characteristics of the real thing.

This simple explanation of a complex process underlines why a separate graphics processing unit, a computer within your computer, is required to play the games of today. Video cards take the onus of graphics off your CPU, freeing up space to run the rest of your game.

 

[Kanyamagufa]

I'm just curious, dare are I ask what this is for?

The only reason I bring it up is that it may help if we knew what type of audience was receiving the paragraph.

 

[Dyno]

I think the title says it all. These people are very low-tech. It's to inform them about computer basics one component at a time. Think of it as if your mom or dad is going to buy a computer.

Well, maybe not your mom or dad. I don't know them, they could be quite computer savvy. Let's say my mom or dad, who are not.

We're talking correct mistakes on the screen with liquid paper here.