Nicron #98 23 июля 1998

Программирование

Programming - the withdrawal of sprites. continued and answers to questions

      Do not let brains wither -
              Sprite!


(C) Spencer Winset / Diamond group



    I got the first letter, it is from the famous Moscow
free-coder GPV-SOFT (500:95 / 550.5, tel :944-04-48 George):

GPV> Hi, in your letter you said a lot, but no conditions.

All conditions, I would not have received any letter. 
Especially, I would like to ZX-folk a little practice in 
thinking, why not put a restriction on the flight of thought 
(although you're right). 

GPV> I understand - you need the output sprite XOR.

That result, you reflected upon my squiggles (again you right).

GPV> Why did not you tell how much memory you have,
GPV> what size the sprite, using a second screen, etc.

The answer I gave to the eleven lines above. And in fact: memory
little sprites: the width of 2 or 3 characters. Pos., height 
about 16 lines second screen is available and free to all 
registers, '-nye too. By the way, the memory can not DJNZ'it to 
count the lines in the sprite, and paint everything (although 
it is 15 times more bytes will take). 

GPV> If the memory of many, the fastest way to output to XOR:


     LD A, (HL)

     XOR # NN 25 cycles of 1 byte

     LD (HL), A

     INC L

Here in this place until you have earned bottle of beer. And on
tact, mulberries get more 25, but not the namnogo, but to
my procedures, it is also true, namely, the transition to the 
next line (from memory: simple addition of register pairs, and 
on the screen: an international procedure DOWN HL). 

GPV> For each sprite has its own procedure. These procedures 
can be GPV> optimized for the peculiarities of these sprites.

GPV> It all depends on the specific conditions!
GPV> Sincerely, GPV-SOFT (500:95 / 550.5, tel :944-04-48 George)

    Golden words! Many thanks for your letter and advice.

            *


   Now I will try to explain why, in fact, it's all
necessary, and to give more technical information to 
stakeholders. 


   Eighteen months ago, our Diamond group consisting of 8 
people decided to seriously engage in the production of toys 
under the name "X". Because their ideas were absent, it was 
decided to transfer game "WORMS" the platform ZX. We received a 
blessing and KSA code support FUX'a (parabolic flight path

projectile). Less than three months, as a super-grafista 
HUNTER'a drafted into the army. Further, the game went awry, 
and we rushed to a light bread - demostroenie. In 1997 around 
12 demos, the best exercises for training in the codes are not 
found. During this time the accumulated many of their own 
ideas, a copy of the game "WORMS" has turned into a solo 
project. In early 1998, the project has been thawed. Many of 
the procedures were oprimizirovanny almost doubled, and this is 
not the limit. Grafist come from the army, 3 months after 
FunTop98 (there will be his work), and while I (Spencer) 
tighten procedures to the finish line. 05.26.1998 at Council 
sisopov in Izmailovo park our organizer Re-Animator voted. Of 
the 25 names proposed game project has been chosen: "FOUR 
RASCALS" / Four bastards / because in each team of four 
soldiers, the further the game is too early to give information 
(which may jinx). 


   Technical info on sprites.

They overlap (for XOR) in memory for relief, which is also in
sprite form (all bytes are sequentially). Why
for XOR, rather than a mask? First, the clocks and memory in two
times smaller, and secondly, for the relief of black (as in 
Tank War), masks, and will not be seen. And why not direct 
downloading: 

                        POP DE
                        LD (HL), E
             32 / 2 = 16 cycles per byte INC L
            (This is not the limit; LD (HL), D
             and can be ...) INC L

But direct downloading 'upper' sprite PREVIOUS score if they
located in one spot relief, and relief is not a straight line
will be overwritten. Interestingly solved this problem VDV CORP 
in their game ICE CLIMBER: big sprites are printed and rubbed 
each other, but all the sprites in one interrupt are printed in 
one (lyuboy!) sequence, and another break in the strict reverse 
order. See for yourself in the above (y) aforementioned game by 
selecting two players and the "stepped" by one another. And so 
- shimmer a little bit.


  And on XOR'u can use the procedure a second time, and sprite
away from the old position, and accidentally damaged the relief 
is restored. But if someone has a more modern knowledge in this 
area, so please - write, because the game I'm doing not for 
himself but for our Speccy. Bye. 


                   Spencer Winset / Diamond group
                   500:95 / 550.8 Evgene Goljakov