Ton vd Pol

Hi all,

I read some posts about problems with AMD processors. I am not sure my issue is caused by that because I have a different processor from the ones I read the posts about.

The issue:

I have a simple ball sprite. I create a pong-like game. When the ball moves it produces a blurry trail behind it. Like you have with comets in space. The faster the sprite moves, the longer and more noticable the trail.

In response to this I have updated the drivers for my processor and grapics card.

The result is the same.

Beside the blurry trail I notice the movement is always a littlebit choppy. Not extreme, but I think it ought to be somewhat smoother than this.

So no I am wondering what might be causing it. Can it be the processor or the graphics card. Or maybee it is the monitor On LCD tv's I've seen the same effect watching a soccer game.

My configuration:

AMD Sempron 2800+ / 1,61 Ghz / 512 MB

Geforce 6800 Xtreem

Philips SL120 LCD monitor

Thanks,

Ton



Re: XNA Game Studio Express Blurry trail on sprite movement

teh_programerer

I'm guessing it's your monitor, try it out on a CRT, if the ghosting still occurs, then it's a problem with the computer. My monitor does it for my laptop.





Re: XNA Game Studio Express Blurry trail on sprite movement

iainbyoung

It does sound like the monitor may be at fault.

My system (AMD 4800+ with a Samsung 8ms lcd display) display no ghosting / blurring at all with fast moving sprites through XNA. The symtoms you describe to sound typical of the slower lcd displays (although I've no idea what refresh rate your lcd runs at).





Re: XNA Game Studio Express Blurry trail on sprite movement

neogir

 iainbyoung wrote:
The symtoms you describe to sound typical of the slower lcd displays (although I've no idea what refresh rate your lcd runs at).

It doesn't regard the monitor refresh rate. The right property to be investigated  is a response time.  Due to Google search has been failed and the Philips website does not mention the model specified  I can guess it is not a fresh LCD model. If so, it  probably  has  the response time of 40-50 milliseconds or more. The LCD with more than 20-30  ms response time does not fit for a gaming. Modern LCDs typically have less than 8 ms  but it depends on manufacturer honesty  (btw only 2 ms has mine).  I'm shure you can use the TV out  of your graphics card  to have a comparision test .





Re: XNA Game Studio Express Blurry trail on sprite movement

iainbyoung

Sorry, I meant response time, not refresh rate. Obviously I haven't had enough coffee this morning yet :D





Re: XNA Game Studio Express Blurry trail on sprite movement

Ton vd Pol

It is an older TFT monitor. That is right.

What response time is (approximate) the minimum for moving sprites without such site effects

Is 12 ms suitable, or should it be faster

I know "the faster the better", so that answer can already be skipped :)





Re: XNA Game Studio Express Blurry trail on sprite movement

neogir

If you tell me what is the method used to determinate these 12 ms i could be able to answer. There are some tricks by manufacturers to declare low timings.
What does "a response time" means in reality In terms of the ISO 13406-2 standard it is a sum of two (i have simplified a bit):
1) time elapsed since the pixel is on electrically and its luminance is getting from 10% -> up to 90%
2) time elapsed since the pixel is off electrically and its luminance is getting from 90% -> down to 10%

Unfortunately, the standard does not set the common methods what and how to do. The timings are quite different for swithcing on and off, for black and white or halftone fields. It's the wide range for a marketing department to interpretate the timings.
Quite often the response time is shown with the remark "from gray to gray" but a gray color really is any color between black and white. To have a compatible result you'd visit some expert site used the consistent comparative measurements for all the marketed LCDs, f.e. http://www.tomshardware.com/graphics/displays/index.html.

As to your question once more - if the 12 ms is referenced in the LS120 docs it is not true. If 12 ms means the response time of a modern LCD (not older than one year) you want to buy, it sounds like true and may be accepted. But you'd always try before buy!





Re: XNA Game Studio Express Blurry trail on sprite movement

ProfEclipse

It's pretty simple to figure out. At 60Hz refresh rate you need at least 1000/60 ms response time (16.6667). At 75Hz refresh rate you need at least 1000/75 ms response time (13.3333). Basically, your response time has to be the same or less than the time for one frame of refresh.

 (But as neogir pointed out, your mileage may vary.)





Re: XNA Game Studio Express Blurry trail on sprite movement

Ton vd Pol

Ok, I dug into the details a littlebit more. According to docs I found it is a 150S instead of the reported SL 120 by Windows.

I think I can savely asume the monitor is the problem. On internet I found out the response time they report is 50 ms.

Thanks for learning me something.
Now onto the hunt for a good monitor...

Ton