Hey, Please learn me!

[rEaL iGoR]

Hey, I'm trying to learn Direct Draw 7. But it is kind of hard.

MainDesc.lFlags = DDSD_CAPS Or DDSD_BACKBUFFERCOUNT
MainDesc.ddsCaps.lCaps = DDSCAPS_PRIMARYSURFACE Or DDSCAPS_FLIP Or DDSCAPS_COMPLEX
MainDesc.lBackBufferCount = 1
Set PrimaryBuffer = Motor.CreateSurface(MainDesc)

What are the 'caps'?? Can anybody explain deep how this works?
What are the difference between DDSCAPS_COMPLEX, DDSCAPS_FLIP and DDSCAPS_PRIMARYSURFACE ?
And what are the difference between DDSD_CAPS and DDSD_CAPS2? Or 3?

[Zaei]

CAPS, very simply, are the capabilities exposed by your video hardware. Basically, any video card that supports an API has certain things that it supports, and will do for you. For example, in D3D8, there are some newer technologies, Pixel and Vertex Shaders being a good example. Pixel Shaders are only supported in hardware on the newest video cards (geForce 3, and possibly 2, i dont know, those are examples). On just about any other card, if you try to use them, either your program will crash,m or something wierd will happen. To prevent this, you ask the device to enumerate its capabilites for you, and you can then check for support. On older cards, you wont be able to use pixel shaders, so you wont find that in the CAPS. On newer cards, it will be there, so you can use them. I hope this is all making sense =).

Z.

[rEaL iGoR]

So you're saying that if possible, my program will use PrimarySurface(Whatever that may be :P) If my video card cannot support it, it will attempt to use Flip, and so on? So what I'm doing is to check the capabilities of my computer to create the backbuffer...?

But...

MainDesc.lFlags = DDSD_CAPS Or DDSD_BACKBUFFERCOUNT

What are the Flags? Is this if the computer has no capabilities? Zaei, you have any place where to find any background of this type of programming which goes really deep, cause I think asking you from here might take a lot of effort for the both of us So if I had a place where I could find out WHAT the different components are and how they work, it would be a lot easier to use it

[JDYoder]

This site may prove helpful. Check out the DX7 stuff from the top of the menu...

http://64.23.12.52//index.asp

[rEaL iGoR]

I know about that site. As a matter of fact, I got my code from there. That site is GREAT, but he's left out a few details in the code so some of it seems like some kind of a recipie.
!!THAT'S NOT GOOD IN A TUTORIAL!!

[kedaman]

Besides looking for tutorials (which is good for learning but they might not be informative enough somtimes) you can look up certain things in the SDK's documentation. MSDN is another good source, look under dwFlags here:
http://msdn.microsoft.com/library/de...trcts_2y7b.asp

[rEaL iGoR]

Hey. I've noticed that when to make all the flags valid etc, you use the Or-operator. Why is that? Why not 'And'?

[kedaman]

Or and And have actually two uses. They are both boolean logic operators and bitwise boolean logic operators. Between boolean datatypes boolean logic is applied while between numeric datatypes bitwise operation is performed. Here's the results of the boolean operations:

0 And 0 = 0
0 And 1 = 0
1 And 0 = 0
1 And 1 = 1

0 Or 0 = 0
0 Or 1 = 1
1 Or 0 = 1
1 Or 1 = 1

If you replace 1 with true and 0 with false you have boolean logic, if you stack up them like this:

   01000101
OR 10000011
____________
   11000111

you perform bitwise boolean logic. Bitwise boolean logic are as said performed between numeric datatypes like long, a 32 bit integer. All numbers can be written in any decimal system but computers store them binary, which means only digits 0 and 1 are used. A 32 bit integer consists of 32 bits, 32 0's or 1's that is. When bitwise boolean logic is performed, boolean logic is performed between each pair of bits, which means they won't interfer with each other. Flags are basically bit's wich means something, so a 32 bit integer has 32 flags, 32 on/off switches so to speak. When you peform boolean Or, you actually put on all switches that are on in one of the operands Or both, when you perform boolean And, you only get the common switches, that is those that are both in the first And the second operand.
Bitwise boolean Or is performed here to flag on new flags and preserve old ones as well.

[scoutt]

I don't post in here often, basically read the post as I am new to the graphics era, but I just wanted to say that, Kedaman, you explained that really good, even though I already knew that. well done

[DaoK]

SCoutt i know that not related with the topic but i like your icon under your name 8)

[scoutt]

he he thanks

[Zaei]

Unfortunately, Igor, if your video card cannot support an option, the application will probably quit, instead of doing what i can do. Its your job as the programmer to figure out what the computer is capable of, and use it.

Z.

[rEaL iGoR]

So you mean it's my job to make the application search through the computer for components available and stick to them?? GOD DAMN, I'm giving this up! I'll stick to making the graphics, not the engine. Better find me one who can. How 'bout it, Zaei?

[Zaei]

You know what Im working on =P. Ive got little time to do anything else as it is =).

Z.

[kedaman]

Actually DirectX does it for you, not you, you just need to play with the cute api's

[Zaei]

Not true, kedaman, at least for most of the things I have seen... If you dont have a T&L video card, and you try, for example, to create a D3D Device with the flag D3DCREATE_PUREDEVICE, it will fail. Same for choosing an incorrect BackBuffer format, etc. This is all from DX8, but it should hold true for earlier versions.

Z.

[kedaman]

Not true Zaei
On each DirectX component there's a neat GetCaps() function that fills in all hardware accelerated capabailities supported

[Zaei]

But you, the programmer, still has to make sure the device has the capability to use whatever advanced technology before using it. DirectX does not automatically make sure you can do what you want to do, and compensate if you cannot.

Z.

[Crow]

Hey Real Igor,
Don't give up on DX7 - I am a newbie myself, but
once I got going with DX I found it very easy to
use. The trick with it is that you don't have
to worry about much in the beginning. DX will
substitute most hardware functions that it can't
find with it's loverly library of software
support.
What your code is doing is :
1) Telling whatever looks at your surface that it
has a back buffer.
2) It's your primary (what's seen on the
screen), complex surface (there is more than
one) which you want to flip between. Flipping
is just the means by which you copy from the
back buffer to the screen.
3) Tell it there is only one back buffer.
4) And create your object.

DX is all about filling in structures, then using
them with funky functions to get the results.
When you get to optimisations, etc, (which is
what I am trying to deal with now) you do have
to write some specialised code because some of
the software functions are a tad slow (bitmap
rotation for example), but for learning's sake,
ignore that for now and just step through your
engine. You can always touch it up later.
Oh, and don't expect your learning code to be
much use to your finished product. By the time
you are done, you will know much better ways to
do things, and will want (yes, want) to start
with a clean slate.
All my DX experience has been with MSC++ so take
all this with a grain of salt, but the DX stuff
should still all be the same.
Good luck with it.
Steele.

[Sastraxi]

I've been doing some DX7/8 in my "travels" and spare-time, so here's what I've learned:

1. Most tutorial writers put in a lot of extra junk that you won't use unless you know what it is and add it in yourself. Eg. In Jack's program, he has a bRunning variable, I never use it. Actually, most of the framework for my app comes from http://rookscape.com/vbgaming/ . The part about loading a bitmap in ddraw is gold, has all the basics, no bells nor whistles. It's perfect. All you have to do is set everything to nothing when you're done.

2. Experiment with Primary.Flip / Primary.BltFast (...). The Flip is limited by your monitor's refresh rate ANDed with your video card's refresh rate. If I didn't do that math right, it means that it takes the lower of the two. My Optiquest/GeForce2MX combo goes at 150hz, when I ask it to, which is absolutely fine for games, 60 is really all that you need. BltFast/Blt isn't limited, but it's slower usually, and some weird things happen (my frame rates dipped to 0.1 fps when there was no text on the screen, weird, eh?), but once you solve these you'll be on your way.

3. A final word; use 24/32bit colour depth, spare yourself the idiocy of 16-bit. Believe me, dont go 16/15 and it will be WORTH it. Also, 8-bit is fine for things such as starfield simulators, set the primary surface's palette to 0,0,0 - 255,255,255 for a complete grayscale screen.

>=) Good luck!

[kedaman]

No Zaei, that is the end user's issue, he has to have a monitor for playing Quake, otherways he can't see what he's doing Furthermore DirectX is built with a interface that delegates functionality to both hardware acceleration layer and hardware emulation layer, the second if the first is not supported.

[Sastraxi]

But you have to have better than a 2"... that's what Zaei is getting at, I believe. Also you cant play it if you have a B&W hercules card!

[rEaL iGoR]

Thanx for the advice and help, everyone. Unfortunately, I'll have to put the project on the shelf for a while (NOT TOW, if that's what you're thinking, Sas). That includes, Main Instrument(Oh, I'm gonna get GOOD!), A musical project (Where I play the piano), misc. school stuff, etc, etc (Bet you're not really that interrested anyway). So I guess I'll learn DX some other time Good night, fellow earthmen!

[Zaei]

Im getting a good debate with kedaman on this one =). Perhaps DX7 is different then DX8, but I know that in DX8, you can create your D3D Device in (at this point) either the HAL mode, or the REF mode. HAL is, of course, Hardware, while REF is the software version of the entire DX8 functionality. While running in HAL, it will not revert to REF for stuff that isnt supported by the card. Itll just not do something, or do something wierd.

Z.

[kedaman]

Yeah that was sort of what I was pointing at. The devices that HAL supports can easily be determined with GetCaps and I'm refering to DX8 as well