Tempest settings - solution to 'no bullets' problem

[Boonanny]

Arguably my favorite game ever was Tempest (and a close second was probably Battlezone, and then probably Star Wars so I guess I was a vector guy), however I have struggled to get them to look good on my CGA arcade monitors.  Getting vector games to look good enough to play was especially problematic for me when I moved to GroovyMame, particularly for Tempest.

I searched around in here, read a lot of suggested vector.ini settings, but no matter what I tried the stupid bullets would NOT show up in Tempest.

So, I finally stumbled on the solution and I have no explanation for why it works, but it does.  I figured I'd post it to help some sad soul tormented by this silly problem in the future.

Okay, first the best technique to tweak in vector settings:
Rather than adjusting settings in vector.ini and then loading up the game from command line to see the effect, use the tab menu and tweak the slider settings in real time.  This allows you to tweak the vector settings and see the effect immediately.  For Tempest, start the game, shoot a bunch of (invisible) bullets, hit pause while they are still on screen, go to the tab menus, and start tweaking all the vector display slider settings until you get the best possible display.  Much faster and easier.  Key factors to tweak: gamma, contrast, and beam width.  I also like to make  sure the brightness keeps the black levels down so you can't see the 'game rectangle' edges against true black.

Now, the mysterious solution to the bullets:
It turns out that on my setup of screen + groovy, no version of tempest shows bullets at all unless the beam width is set to OVER 2.0.  At 2.0 and below there are simply no bullets displayed at all. Any setting even fractionally over 2.0 and the bullets are fully displayed perfectly.

So, once I found that "switch", I was able to tweak the contrast and gamma to get a pretty respectable looking display.  Its not an emulation of the old vector monitor effects of course, but it looks pretty darn good in my opinion and is very playable.  I wrote down the numbers, updated vector.ini accordingly and now pretty much all my vector games are decent looking and playable and most importantly TEMPEST HAS BULLETS AGAIN!!!

By the way, many many thanks to Calamity and to this community.  My MAME experience has been so much improved since I switched to Groovy!  Love it!

[Calamity]

Hi Boonannay,

Thanks a lot for sharing this.

The only explanation I find for this fact is that it's some sort of artifact due to interlaced video. When rendering a normal 60 Hz game with interlaced video, only half of the information is shown for each frame, alternating between even and old fields. So in theory it is possible for an object that is 1 pixel high to move up or down the screen and become invisible, provided it always falls on an even line when the odd field is being displayed and vice versa. But I had no evidence of this becoming evident in a game.

[Boonanny]

I thought the same thing at first, because I couldn't remember what the bullets looked like exactly.  However, this problem does not exist for Asteroids, which does use little one pixel dots for bullets.
Then, once I got it working I realized that the Tempest bullets are actually pretty big  - they look like squares with "sparks" around the edges, definitely many pixels per bullet. 
Here is a screenshot from the web:


So, I have no explanation, but I'm just glad to have stumbled across the solution. 

I found your "donate" button finally and made a contribution a couple of days ago. Hope you got it.  Thanks again for all your work on Groovymame.

[Boonanny]

By the way, for those many people enjoying Groovy MAME and CRT Emudriver, and especially those getting awesome free tech support...
Here is the donations page:
http://code.google.com/p/groovyarcade/

Calamity is the one on the right. 
If you have the means, please remember to support "free" software that you use and love.