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Mike Harris

Do all TI Games use Sprites?

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I was playing Blasto the other day and I noticed that the tank is not a smooth ride.

 

So I am really curious if the Tank is just a set of tiles that jumps from area to area or is that just how the sprite is programmed to move.

I really like the game and I was interested on the inside scoop.

I've seen similar things in many TI99 Games.
A programing technique?  Limitations of the TI99?  A signature of the programmer?

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Posted (edited)
4 hours ago, Mike Harris said:

So I am really curious if the Tank is just a set of tiles that jumps from area to area or is that just how the sprite is programmed to move.

The tanks are sprites.

4 hours ago, Mike Harris said:

I've seen similar things in many TI99 Games.
A programing technique?  Limitations of the TI99?  A signature of the programmer?

Most programming languages for the TI have access to sprites. There's 32 sprites, but the TI will only show a maximum of 4 of these horizontally. Distribute the sprites vertically and you can have all of the 32 sprites on screen at once.


blasto.gif.affc3421c21c7cebce3d9143dbe084dc.gif

Edited by sometimes99er
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20 hours ago, Mike Harris said:

I was playing Blasto the other day and I noticed that the tank is not a smooth ride.

 

So I am really curious if the Tank is just a set of tiles that jumps from area to area or is that just how the sprite is programmed to move.

I'll take a stab at this...

 

In Blasto it appears we have sprites that are moved 8-pixels at a time purely by the programmers technique.

 

Sprites are not bound by the 32col*24row grid used for character graphics. So, the tank movement does not need to be jerky like that. The programmer is probably just trying to avoid intermediate positions for the tank, where shots won't necessarily meet their targets head-on. Its a way to simplify collision detection. This approach greatly simplifies the code because it forcibly lines up objects on the play field.

 

All 32 sprites may smoothly move along one pixel at a time on a 256*192 grid. More on sprite positioning and movement, page 25: http://www.digitpress.com/library/manuals/ti994a/ti extended basic.pdf

 

spritequote.thumb.png.ec1415fe7a762365dcd2d23eccfe6e8c.png

 

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Posted (edited)
Quote

Do all TI Games use Sprites?

No, not all, but many do. Most games (thousands) are written in TI Basic and TI Extended Basic. TI Basic hasn't access to sprites (apart from a few hacks and extensions). TI Extended Basic has good access to 28 of the sprites, and they're used a lot. The rest of the games (hundreds) are cartridges written in GPL and Assembly and other stuff (different languages and formats).

22 hours ago, Mike Harris said:

So I am really curious if the Tank is just a set of tiles that jumps from area to area or is that just how the sprite is programmed to move.

I think the designer(s) thought the tanks would be too small on a fuzzy television, if they should fit in an 8x8 pixel character, so slightly bigger sprites were chosen. I'm not sure introducing sprites in Blasto simplified anything (much easier to keep it all character based). The fire from the tank cannon is also a sprite. It starts out under the tank and also moves at 8 pixels per frame. Interestingly the fire is displaced 1 pixel vertically.

 

image.png.5048da00466453e98e3d894547028399.png

 

image.png.f9398681ffb2b5e6d78dd54fa5c4495f.png

 

The fire is light yellow on light green. Nice contrast. Tanks a lot.

Edited by sometimes99er
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Where did you get such a clear picture of the pattern, background and colors?

I can look online all day and can't find this stuff or any information about moving 8 pixels at a time.

You have the source to study as well?

I am curious about the logic.

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1 hour ago, Mike Harris said:

Where did you get such a clear picture of the pattern, background and colors?

It's fairly easy to set up TI-99/4A emulators like Classic99, JS99'er and MAME to show "crisp graphics". This is how I prefer Classic99: 1. Filter Mode / None. 2. Stretch Mode / DX. 3. Video / Change Size / 2x. Classic99 has the ability to disable (and enable) sprite and background layers: Video / Layers / ...

1 hour ago, Mike Harris said:

I can look online all day and can't find this stuff or any information about moving 8 pixels at a time.

Well, let's stick with Blasto. I video recorded while playing for a bit, then went back, singlestepped and looked at the frames (60 frames per second).

1 hour ago, Mike Harris said:

You have the source to study as well?

Nope.

1 hour ago, Mike Harris said:

I am curious about the logic.

I don't know much about the game, so I can only guess about game rules etc., but it seems like a fairly (or extremely) easy game to remake on most modern and retro platforms.
 

 

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On 8/10/2019 at 10:32 AM, Airshack said:

Note: Blasto is a TI-99/4A port of this 1978 arcade game by Gremlin.    https://en.wikipedia.org/wiki/Blasto_(arcade_game)

 

 

 

 

It's interesting to realize which games were based on relatively obscure arcade games.

 

This is just speculation... but I wonder if Lubbock TI programmers like Jim Dramis and John Philips chose games to do based on what arcade machines were around.

 

Blasto was by Milton Bradley.. but Car Wars was developed in Lubbock.


There was a very large arcade near TI in "The Well" at Texas Tech.

 

Perhaps The Well had Rally X, Dodgem which Car Wars was based on. (I never saw a Rally X  Dodgem until an arcade auction in 2010.) Perhaps they had games from the late 70s, unlike other venues that bought/rented only the newest machines. Every gas station or grocery store had one or ten games circa 1982-1983... that must have true everywhere right?

 

If I was really lucky I would get to go to The Well for a few minutes after a TI users group meeting in the Texas Tech library. (meetings were on school nights.) But I didn't have eyes for any very old games.. I remember The Well had Jungle Hunt, Tron and Gorf.

 

I spent most time at other arcades like Pistol Pete's on 50th, and smaller "venues". my mental map of Lubbock consisted of where the arcade games were. Maggio's Pizza next to the TI dealer Unisource: They had 25 games, including  Q*bert and Mad Planets.

 

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30 minutes ago, FarmerPotato said:

You are right. I got the name wrong. Dodgem was the game I saw and played for the first time at that auction.

 

 

 

there's also exidy's crash and gremlin's head on..  all the same basic gameplay

 

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Another question about Blasto is why "Trademark Milton Bradley." I know they wrote it but how do they get to claim the trademark on a Blasto port? I suppose MB purchased the rights to Blasto?

 

By 1978 Sega owned Gremln: https://en.wikipedia.org/wiki/Gremlin_Industries

 

Then in 1979 Car Wars comes out which is an obvious clone of Gremlin's Head On. I suppose Car Wars style games were all over the place without legal measures being exercised. Much like the multiple versions of Space Invaders everywhere back then. Crazy how you could just steal ideas back then and make no effort to share the credit. 

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Some companies obtained the rights to certain media type distributions.  For instance, Parker Brothers had the rights to distribution Frogger on cartridge media, while Sierra On-Line had rights for magnetic (disk and tape) media, and Coleco had a license to produce a tabletop arcade unit.  My guess would be Milton Bradley obtained rights for a cartridge or TI-specific release of Blasto and thus the resultant product was MB's copyright.

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On 8/10/2019 at 1:02 AM, sometimes99er said:

No, not all, but many do. Most games (thousands) are written in TI Basic and TI Extended Basic. TI Basic hasn't access to sprites (apart from a few hacks and extensions). TI Extended Basic has good access to 28 of the sprites, and they're used a lot. The rest of the games (hundreds) are cartridges written in GPL and Assembly and other stuff (different languages and formats).

I think the designer(s) thought the tanks would be too small on a fuzzy television, if they should fit in an 8x8 pixel character, so slightly bigger sprites were chosen. I'm not sure introducing sprites in Blasto simplified anything (much easier to keep it all character based). The fire from the tank cannon is also a sprite. It starts out under the tank and also moves at 8 pixels per frame. Interestingly the fire is displaced 1 pixel vertically.

 

image.png.5048da00466453e98e3d894547028399.png

 

image.png.f9398681ffb2b5e6d78dd54fa5c4495f.png

 

The fire is light yellow on light green. Nice contrast. Tanks a lot.

Speaking of Contrast...
You say that it is yellow on light green then what are those little trail squares?
Regular Green or Dark Green?
What classic99 gives me some weird colors compared to mame and what I know is on the Colecovsion which uses a similar GPU.

Also, how can you tell if that is yellow yellow or light yellow.

What color are the explosions?  Light Red, Dark Red or just Red?

Classic 99 debug tells very little at least that I can decipher.

Edited by Mike Harris

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7 hours ago, Mike Harris said:

Speaking of Contrast...
You say that it is yellow on light green then what are those little trail squares?
Regular Green or Dark Green?

Dark green.

7 hours ago, Mike Harris said:

What classic99 gives me some weird colors compared to mame and what I know is on the Colecovsion which uses a similar GPU.

The colors were and can be perceived differently depending on many factors (system (NTSC/PAL), the individual television, modulator etc). An emulator typically selects its TI palette from millions of colors. Win994A has a very dark blue.

7 hours ago, Mike Harris said:

Also, how can you tell if that is yellow yellow or light yellow.

The color codes are stored in the VDP, but otherwise Classic99 has a fixed palette, so if you take a screenshot, you can rather easily determine which color is used.

7 hours ago, Mike Harris said:

What color are the explosions?  Light Red, Dark Red or just Red?

Dark red.

 

Edited by sometimes99er
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