New TI Game: Sneak peek

[Cebus Capucinis]

LOL! I read the thread and thought you were porting 2600 "Sneak n' Peek" to TI, as I thought that was the title!

 

I couldn't imagine why anyone would want to port a terrible U.S. Games 2600 game to anything!

 

Looks very cool!!!!

[JonArkanix]

Oh wow. Could you link it up here? My iPhone doesn't recognize the signature link that sometimes99er mentioned. I would love to read up on it!

Sure, you can check out this thread on our forums for a few recent updates ... http://www.c64dev.com/forum/viewtopic.php?id=203

 

We released an early preview in September 2009 which is now outdated compared to internal previews. We'll release another preview this summer.

[jchase1970]

Hey Adamantyr,

 

I'ld like to make a suggestion that you use save codes on this game, not disk saves so people can play it even if they don't have a disk expansion.

 

John

[+adamantyr]

Hey Adamantyr,

 

I'ld like to make a suggestion that you use save codes on this game, not disk saves so people can play it even if they don't have a disk expansion.

 

John

 

It's possible to do. Save codes are just an encryption key, would be a bit of fun to put one together.

 

Adamantyr

[jchase1970]

Hey Adamantyr,

 

I'ld like to make a suggestion that you use save codes on this game, not disk saves so people can play it even if they don't have a disk expansion.

 

John

 

It's possible to do. Save codes are just an encryption key, would be a bit of fun to put one together.

 

Adamantyr

 

 

I was assuming you are making it a cartridge? If it's disk base then I guess they would have a disk to save it on, lol.

[+adamantyr]

I was assuming you are making it a cartridge? If it's disk base then I guess they would have a disk to save it on, lol.

 

No, wasn't planning on a cartridge, so yes, could just save games to disk. It's not possible to really do what I want with the game in only 256 bytes of RAM easily, and if I have to require 32k, may as well require the disk system too.

 

Adamantyr

[+adamantyr]

Picked this one up again... doing some graphics fun.

 

[+Ksarul]

Nice changes!

[Iwantgames:)]

Nice

[Asmusr]

This is really exciting. RPG games are probably the only type of games on the TI that would be able to catch my attention for more than a few minutes. In the past I have probably been playing Angband more than any other game despite its lame ASCII graphics because it has a huge depth in the way you can develop your stats, the items you can collect, and the monsters you can meet.

 

Is this an assembly language project? Are you planning to run this in full or 'half' bitmap mode?

[+adamantyr]

Assembly language, and in half-bitmap mode. I agree, RPG's are the best for depth and nuance!

[gregallenwarner]

What's the difference between half-bitmap and full-bitmap? Is it like running in bitmap mode, but using tilesets like in graphics mode?

[Asmusr]

What's the difference between half-bitmap and full-bitmap? Is it like running in bitmap mode, but using tilesets like in graphics mode?

 

Yes. In full bitmap mode you have 3 tilesets of 256 tiles - enough to have a separate tile for each screen position. In half bitmap mode you only have one tileset that covers the entire screen.

[TheMole]

Picked this one up again... doing some graphics fun.

 

kq3.png

 

Very nice improvements on the trees specifically (the rest as well, but the really jump out to me). Please make this!

[gregallenwarner]

Yes. In full bitmap mode you have 3 tilesets of 256 tiles - enough to have a separate tile for each screen position. In half bitmap mode you only have one tileset that covers the entire screen.

Is there only one tileset in VRAM? Or do you duplicate the one tileset three times?

[Asmusr]

Is there only one tileset in VRAM? Or do you duplicate the one tileset three times?

 

Only one. You can read about it here.

[gregallenwarner]

Very handy! Did not know about this graphics mode!

 

Edit: I'm reading, and I'm trying to understand this address mask notion, and I'm not really getting it. Can someone explain what that is and how it works?

Edited October 4, 2014 by gregallenwarner

[Asmusr]

In full bitmap mode the VDP can read patterns from one of three tables (depending on the screen position) at either >0000, >0800 or >1000. The address is AND'ed with the mask before a read. If the mask is >07FF, for instance, the VDP will always read from the table at >0000. If it's >1FFF as in full bitmap mode the VDP can read from either table. The color tables have a similar mask but the color tables are in >2000, >2800 and >3000 (or you can swap the location of the color and pattern tables). The mask is applied before the base table address (>0000 or >2000) is added.

[gregallenwarner]

Where is the mask stored?

[Gazoo]

Where is the mask stored?

 

In Jim Carry's closet.

 

Sorry, couldn't resist.

 

Gazoo

[Asmusr]

Where is the mask stored?

 

VDP register 3

Defines the location of the color table. Possible values are >00 through >FF and are multiplied by >40 to find the location of the color table. The table is not used in text mode, nor in multicolor mode.

In bitmap mode (i.e. when bit 6 in register 0 is set) the meaning of this register changes: bit 0 (weight >80) is the only one used to determine the address of the color table, which means the table has only two possible locations: >0000 or >2000. The remaining bits are used to define the table size, by the way of an address mask. This is done as follows: the righmost 7 bits are shifted left by 6 positions, filling the rightmost bits with 1s. The result will be a number between >003F and >1FFF, which is ANDed with the address of a character in the table. As a result, the table can have any size between >40 and >2000 bytes (however, note that the maximal usable size is >1800: 3 times >800 bytes).

VDP register 4

Defines the location of the character pattern table. Only the last 3 bits are used, thus possible values are >00 through >07. The value is multiplied by >800 to find the location of the character pattern table. Each entry in the table is eight bytes long and define the pattern of a character, in numeric order. Each byte in an entry defines one line of pixels in the character pattern: bits set as 1 result in foreground color pixels, bits set as 0 encode background color pixels.

In text mode (i.e. when bit 3 in register 1 is set) the last two bits of each byte are ignored since characters are only 6-pixel wide.

In bitmap mode (i.e. when bit 6 in register 0 is set) the structure of this register changes: bit 5 (weight >04) is the only one used to determine the address of the color table, which means the table has only two possible locations: >0000 or >2000. The two rightmost bits are used to determine the length of the table, by the way of an address mask. This is done by shifting them 11 positions to the left, filling the righmost bits with 1s. The result will be a number between >07FF and >1FFF that will be used as an address mask. At least, this is what happens in bitmap + text mode (i.e. when bit 3 of register 1 is set). In standard bitmap mode, the righmost bits are not necessarily 1: they are taken from VDP register 3, i.e. the address mask of the color table is used for both the color table and the pattern table addressing.

[Asmusr]

From js99er.net:

this.colorTableMask = ((this.registers[3] & 0x7F) << 6) | 0x3F;

this.patternTableMask = ((this.registers[4] & 0x03) << 11) | (this.colorTableMask & 0x7FF);

[Asmusr]

One thing the Thierry N doesn't mention is that the half bitmap modes has problems displaying more than 8 sprites. Additional sprites appear in several places on the screen. Color table masking doesn't seem to affect the sprites, so if you want to use sprites but also want to save VDP RAM you can set up the VDP to use 3 pattern tables and one color table. The pattern tables would just be 3 identical copies.

[+adamantyr]

One thing the Thierry N doesn't mention is that the half bitmap modes has problems displaying more than 8 sprites. Additional sprites appear in several places on the screen. Color table masking doesn't seem to affect the sprites, so if you want to use sprites but also want to save VDP RAM you can set up the VDP to use 3 pattern tables and one color table. The pattern tables would just be 3 identical copies.

 

Hm, that is not documented anywhere, not even on the TI Tech pages... Kind of sucks, you're wasting 4k of space!

 

Has this been tested extensively with real hardware AND emulation? I wonder why the position of the pattern table is impacting the sprite attribute table... theoretically the two registers should not impact one another.

[senior_falcon]

 

Hm, that is not documented anywhere, not even on the TI Tech pages... Kind of sucks, you're wasting 4k of space!

 

Has this been tested extensively with real hardware AND emulation? I wonder why the position of the pattern table is impacting the sprite attribute table... theoretically the two registers should not impact one another.

Missing Link uses this when in the 2 color mode. There are three pattern tables for a total of 6k and one 2K color table that controls all of them. All the bytes in the color table are set to the same foreground color and background color so there are only two colors possible on the screen. This mode works fine on a real TI and on Classic99. It is not compatible with Win994a. I don't know about Mess or any of the others emulators.