Strange glitch in my game (video shows it)

[scotthuggins]

Hey guys!

Below is a link of me showing a weird glitch in my game, Cavern Rescue.

I've tried a good bit to figure it out to no avail. I've heard that sometimes you have to delay a bit to let the hardware catch up to all the things you are throwing at it? If so.... just nop opcodes?

I'd definitely love to hear your thoughts.

youtu.be/_lGmt3Af4tc

Thanks, Scott!

[Malban]

Hi,
a diagnosis from afar is always difficult - and watching the video gives only so many (or in this case - so few) clues.

A question at the beginning, there are different versions of vectrex about.
Did you try on different vectrex? (Buzz/NoBuzz model?)

Does this glitch happen at the "beginnen" of the ships vectorlist or the end?
(If you explained that by audio - I could not listen to the audio...)

Usually when I draw an object I start from zero, move to the location, draw the object and go back to zero.
The glitch vector seems to indicate - that you don't. So the question
above - is it at the beginning or end of that list.

What do you do directly before/after (depending on the answer above)?

The only "known" hardware issue that I know of that might cause something like that is "stalling" of the via. Look at the page

Vide - findings

here I tried to explain it.
The question - do you in anyway do something to the VIA_SHIFTREG within the cycle range described there?

Also a trap one easily falls into in that relation is the "clr" mnemonic.
It is (if you have a reg to spare) nearly always better to do a

 clra
 sta via_shftreg

than to do a
 clr via_shiftreg

Since the second variant "triggers" the shiftreg 2 times (one read one write) - cycle wise it is the same.

Malban

[Rapetou33]

Whatever bug there may be, congrats, Scott, your game is nice and attractive.

[scotthuggins]

Rapetou33- thanks! I really appreciate that. The video quality did not come out so well. It looks much better "in person". It's been a long road coding this, that's for sure! This wasn't easy for me. I guess all home brewers would say the same thing.

Malban- you're right. I thought about posting source code, but there's a lot of it. I'm starting at 0, drawing enemy #1 vector, from there I move elsewhere to draw enemy #2, and then enemy #3 and finally #4. So I'm only going back to 0 when I start the 4 enemy vector list drawings. I will try your suggestion of always going back to 0. I will definitely look at your info in the vide link you posted.

Also, you asked about the model of Veccy I tried this one - I tried it on a normal BUZZ model. It does the same thing on the ParaJVE emulator on my PC.

Lastly, I will definitely check on the "via_shftreg" clearing that you mentioned as I think I might be doing that.

Really appreciate the responses!

[Malban]

Oh...

If the glitch also happens on ParaJVE - THAN it is probably a software feature you programmed :-).

ParaJVE is not that good at emulating the finer hardware issues.
If you want a second pair of eyes - you can mail the the source - or parts of the source.
(or a bin - or a "runnable" source... - since I probably would use a debugger... and debugging a runnable source is much easier .-))

You find a valid email on the Vide pages under "contact".

Regards
Malban

[Mayhem]

Definitely looks good, like a cross between Thrust and Omega Race

[scotthuggins]

Hi Mayhem- thanks for that! If I could get this darn bug figured out, I'd be on cloud 9! Is it just me- but this platform screams Thrust, Omega Race (Omega Chase!), and ALL the Cinematronics arcade releases. Sometimes it is hard to come up with original ideas. Many home brewers have done so, and it impresses the heck out of me.

I'll post a much longer video (there is a bonus challenge stage and other things) soon.

Malban- thanks for offering! I will email you soon. Much appreciated.

Scott

[Malban]

PM sent

[scotthuggins]

Kudos to Malban! He pointed out (very quickly in fact) several glitches in my code that cleared it all up. He also found a bug that I didn't even know was there. Thanks again!

[cNp]

Hey, glad you got it fixed and great looking game, kudos!

[scotthuggins]

cNp- thanks! I am polishing it up more each day. Pumped about releasing it. You know, the most frustrating part of this journey is the visuals aren't 100% the same across different Vectrexes. That was a bummer to find out. I tweaked it as best I could so it's closer on all I can test on, but it's not perfect. It's definitely not a deal breaker or anything, just a little bit frustrating.

Big Blue looks awesome! I tried ordering it (last year sometime) but you had sold out.

Something I wanted to ask you - I remember on the menu of Big Blue you had a calibration option.  Can you explain that feature?  Thanks!