DXDRAW options

**seiferalmasy** · 20-07-2006, 03:30 AM

Well, I looked on the net but didn't see a great deal that helped. A few questions:

1. I am running a 2d game, windowed. Which of the options should I enable in dxdraw? There are a few I am not sure about. a. doallowpallete b. do3d, c. dodirectx7mode (why would I want to go backwards?) d. doretainedmode e. doselectdriver. Also, should I enable to Use zbuffer?

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2. Other thing I had trouble with, I took my game to a mates house, he uses a widescreen tft monitor on some awful resolution. My game was no longer correct looking because the dxdraw had been stetched according to his resolution, like his normal windows. So, how can I stop this from happening so that it appears to be a 600*500 Dxdraw surface on any computer?

Thanks

**czar** · 20-07-2006, 04:39 AM

Just becareful with Do3d and XP.

Floating point operations become single rather than double which can cause hassles it you add two Doubles together. We had problems where 2 + 2 = 3.999999 or whatever.

This only happens with Windows XP.

If you aree doing 2d stuff then zbuffer is false.

As for wide screen - you will haveto take that intop account during design.

Either stick to your aspect ration and wide screen users have black bars on left and right. Or increase the width of the game area.

**seiferalmasy** · 20-07-2006, 04:58 AM

yes, i have been having that problem...thanks

**czar** · 20-07-2006, 05:39 AM

You can set the maths precision back to 32 bit and it solves the problem

**seiferalmasy** · 20-07-2006, 05:41 AM

don't need it anyway

What about usedirectx7mode and selectdriver though? what are they about?

**czar** · 20-07-2006, 07:11 AM

I am not sure. I have never noticed any benefit to setting them.

**Clootie** · 20-07-2006, 09:18 PM

If you are using undelphix with DX9 backend - you could modify CreateDevice call and set D3DCREATE_FPU_PRESERVE behaviour flag. This will disallow Direct3D to hange FP precision to 32bit (single). If your application is not CPU limited this is the best solution.

**czar** · 20-07-2006, 09:23 PM

In my case I just used

Unit Maths

if GetPrecisionMode = pmsingle then SetPrecisionMode(pmDouble);

**seiferalmasy** · 20-07-2006, 11:37 PM

hmm another few questions

On a computer with 4MB graphics card, obviously old, the game runs awfully slow no matter what. I take it that there is nothing I can do on sucha machine.

On a 16MB machine, again must be old, 60 FPS mode runs fine, but vsync mode runs sluggish. This is again a symptom of bad graphics card?

**Clootie** · 22-07-2006, 11:04 AM

Originally Posted by czar

In my case I just used

Unit Maths

if GetPrecisionMode = pmsingle then SetPrecisionMode(pmDouble);

Well, this is not good as it can break Direct3D. You better save current FP control word, do SetPrecisionMode(pmDouble); before your code and restore control word before starting to call DirectX functions. This way you will be sure what everything will work correct and performance will be at top.