I'm wondering how to make 2 things move in turbo pascal 7.0 at the same
time
cause when one is moving and you press the key to get the other object to
move it
cuts the first object off.

Diesel <diese...@geocities.com> schrieb im Beitrag
<01bd260d$33a00f80$664d06d0@default>...

You actually have to use virtual pages ;)
...check this out:

BTW if some1 knows the new series (above 21) please mail me.

                   
                            W E L C O M E        
                     To the VGA Trainer Program  
                                 By              
                         DENTHOR of ASPHYXIA      
                   
                     
                       

                           --==[ PART 7 ]==--

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Introduction

Hello! By popular request, this part is all about animation. I will be
going over three methods of doing animation on a PC, and will
concerntrate specifically on one, which will be demonstrated in the
attached sample code.

Although not often used in demo coding, animation is usually used in
games coding, which can be almost as rewarding ;-)

In this part I will also be a lot less stingy with assembler code :)
Included will be a fairly fast pure assembler putpixel, an asm screen
flip command, an asm icon placer, an asm partial-flip and one or two
others. I will be explaining how these work in detail, so this may also
be used as a bit of an asm-trainer too.

By the way, I apologise for this part taking so long to be released, but
I only finished my exams a few days ago, and they of course took
preference ;-). I have also noticed that the MailBox BBS is no longer
operational, so the trainer will be uploaded regularly to the BBS lists
shown at the end of this tutorial.

If you would like to contact me, or the team, there are many ways you
can do it : 1) Write a message to Grant Smith/Denthor/Asphyxia in private
mail
                  on the ASPHYXIA BBS.
            2) Write a message in the Programming conference on the
                  For Your Eyes Only BBS (of which I am the Moderator )
                  This is preferred if you have a general programming query
                  or problem others would benefit from.
            4) Write to Denthor, Eze or Livewire on Connectix.
            5) Write to :  Grant Smith
                           P.O.Box 270 Kloof
                           3640
                           Natal
            6) Call me (Grant Smith) at (031) 73 2129 (leave a message if you

                  call during varsity)
            7) Write to mcph...@beastie.cs.und.ac.za on InterNet, and
                  mention the word Denthor near the top of the letter.

NB : If you are a representative of a company or BBS, and want ASPHYXIA
       to do you a demo, leave mail to me; we can discuss it.
NNB : If you have done/attempted a demo, SEND IT TO ME! We are feeling
        quite lonely and want to meet/help out/exchange code with other demo
        groups. What do you have to lose? Leave a message here and we can
work
        out how to transfer it. We really want to hear from you!

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 The Principals of Animation

I am sure all of you have seen a computer game with animation at one or
other time. There are a few things that an animation sequence must do in
order to give an impression of realism. Firstly, it must move,
preferably using different frames to add to the realism (for example,
with a man walking you should have different frames with the arms an
legs in different positions). Secondly, it must not destroy the
background, but restore it after it has passed over it.

This sounds obvious enough, but can be very difficult to code when you
have no idea of how to go about achieving that.

In this trainer I will discuss various methods of meeting these two
objectives.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Frames and Object Control

It is quite obvious that for most animation to succeed, you must have
numerous frames of the object in various poses (such as a man with
several frames of him walking). When shown one after the other, these
give the impression of natural movement.

So, how do we store these frames? I hear you cry. Well, the obvious
method is to store them in arrays. After drawing a frame in Autodesk
Animator and saving it as a .CEL, we usually use the following code to
load it in :

TYPE icon = Array [1..50,1..50] of byte;

VAR tree : icon;

Procedure LoadCEL (FileName :  string; ScrPtr : pointer);
var
  Fil : file;
  Buf : array [1..1024] of byte;
  BlocksRead, Count : word;
begin
  assign (Fil, FileName);
  reset (Fil, 1);
  BlockRead (Fil, Buf, 800);    { Read and ignore the 800 byte header }
  Count := 0; BlocksRead := $FFFF;
  while (not eof (Fil)) and (BlocksRead <> 0) do begin
    BlockRead (Fil, mem [seg (ScrPtr^): ofs (ScrPtr^) + Count], 1024,
BlocksRead);
    Count := Count + 1024;
  end;
  close (Fil);
end;

BEGIN
  Loadcel ('Tree.CEL',addr (tree));
END.

We now have the 50x50 picture of TREE.CEL in our array tree. We may access
this array in the usual manner (eg. col:=tree [25,30]). If the frame is
large, or if you have many frames, try using pointers (see previous
parts)

Now that we have the picture, how do we control the object? What if we
want multiple trees wandering around doing their own thing? The solution
is to have a record of information for each tree. A typical data
structure may look like the following :

TYPE Treeinfo = Record
                  x,y:word;       { Where the tree is }
                  speed:byte;     { How fast the tree is moving }
                  Direction:byte; { Where the tree is facing }
                  frame:byte      { Which animation frame the tree is
                                    currently involved in }
                  active:boolean; { Is the tree actually supposed to be
                                    shown/used? }
                END;

VAR Forest : Array [1..20] of Treeinfo;

You now have 20 trees, each with their own information, location etc.
These are accessed using the following means :
                  Forest [15].x:=100;
This would set the 15th tree's x coordinate to 100.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Restoring the Overwritten Background

I will discuss three methods of doing this. These are NOT NECESSARILY
THE ONLY OR BEST WAYS TO DO THIS! You must experiment and decide which
is the best for your particular type of program.

METHOD 1 :

Step 1 : Create two virtual pages, Vaddr and Vaddr2.
Step 2 : Draw the background to Vaddr2.
Step 3 : Flip Vaddr2 to Vaddr.
Step 4 : Draw all the foreground objects onto Vaddr.
Step 5 : Flip Vaddr to VGA.
Step 6 : Repeat from 3 continuously.

In ascii, it looks like follows ...

    +---------+           +---------+           +---------+
    |         |           |         |           |         |
    |  VGA    | <=======  |  VADDR  |  <======  |  VADDR2 |
    |         |           | (bckgnd)|           | (bckgnd)|
    |         |           |+(icons) |           |         |
    +---------+           +---------+           +---------+

The advantages of this approach is that it is straightforward, continual
reading of the background is not needed, there is no flicker and it is
simple to implement.  The disadvantages are that two 64000 byte virtual
screens are needed, and the procedure is not very fast because of the
slow speed of flipping.

METHOD 2 :

Step 1 : Draw background to VGA.
Step 2 : Grab portion of background that icon will be placed on.
Step 3 : Place icon.
Step 4 : Replace portion of background from Step 2 over icon.
Step 5 : Repeat from step 2 continuously.

In terms of ascii ...

      +---------+
      |      +--|------- + Background restored (3)
      |      * -|------> * Background saved to memory (1)
      |      ^  |
      |      +--|------- # Icon placed (2)
      +---------+

The advantages of this method is that very little extra memory is
needed. The disadvantages are that writing to VGA is slower then writing
to memory, and there may be large amounts of flicker.

METHOD 3 :

Step 1 : Set up one virtual screen, VADDR.
Step 2 : Draw background to VADDR.
Step 3 : Flip VADDR to VGA.
Step 4 : Draw icon to VGA.
Step 5 : Transfer background portion from VADDR to VGA.
Step 6 : Repeat from step 4 continuously.

In ascii ...

     +---------+           +---------+
     |         |           |         |
     |   VGA   |           |  VADDR  |
     |         |           | (bckgnd)|
     | Icon>* <|-----------|--+      |
     +---------+           +---------+

The advantages are that writing from the virtual screen is quicker then
from VGA, and there is less flicker then in Method 2. Disadvantages are
that you are using a 64000 byte virtual screen, and flickering occurs
with large numbers of objects.

In the attached sample program, a mixture of Method 3 and Method 1 is
used. It is faster then Method 1, and has no flicker, unlike Method 3.
What I do is I use VADDR2 for background, but only restore the
background that has been changed to VADDR, before flipping to VGA.

In the sample program, you will see that I restore the entire background
of each of the icons, and then place all the icons. This is because if I
replace the background then place the icon on each object individually,
if two objects are overlapping, one is partially overwritten.

The following sections are explanations of how the various assembler
routines work. This will probably be fairly boring for you if you
already know assembler, but should help beginners and dabblers alike.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 The ASM Putpixel

To begin with, I will explain a few of the ASM variables and functions :