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^3                    P r o g r a m   P a r l o u r
            
^2                                T w o

^3                      b y   B e n   A s h l e y

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^1 Last time, we looked at PROGRAM PROTECTION.  This issue though, I`ll
^1be  giving  you  a  tutorial  on  AMOS 3D.  Yes, I know its been done
^1rather  badly, and many people have binned it and ripped it off their
^1AMOS program disks.  But for those of us, who have for some reason or
^1another, KEPT it on, then you might find this tutorial rather nice.

^1 Firstly,  I`ll  give  you  a  full  blown  program, and explain each
^1section  bit-by-bit.   After  that,  I`ll  tell you about the uses of
^1other 3D commands which are not exploited in the 3D demo.

^1 Ok,  so  lets  go.   Load  up  AMOS,  and  MAKE SURE you have the 3D
^1extension loaded in.

^2Now  I`ll  explain  it  all,  bit  by  bit.   So,  I  always start my
^2programs`s with REM`s, the following can be ommited..

^2  ' AMOS 3D Tutorial Program
^2  ' ========================
 
^2  ' Written for TOTALLY AMOS, by Ben Ashley of Odyssey Software
 
^2  ' Please note: Requires the OBJECTS directory, to be in the ROOT 
^2  ' directory, and the file, WB.IFF, to also be in the root directory. 

^1 No Problem.  So now I`ll create a simple, 16 colour LOW RES screen^1^1.

^2  Screen Open 0,320,256,16,Lowres

^1 And  I`ll do a simple setup procedure, of setting colour 1 to white,
^1setting  the PEN and PAPER colours, turning the cursor and flash off,
^1and finally hiding the Mouse and clearing the screen.

^2   Colour 1,$FFF :  Pen 1 :  Paper 0 :  Curs Off :  Flash Off :
^2 Hide On :  Cls 0

^1 Now,  to prevent flicker when displaying the 3D screen, we'll double
^1buffer and autoback it.

^2  Double Buffer :  Autoback 0

^1 If  you don`t have AMOS LIBS on the disk with which you are working,
^1you need a routine to find the AMOS:  disk, and set the drive...

^2    If Not Exist("AMOS:")
^2       Centre At(,10)+"Please insert volume AMOS:"
^2       Centre At(,11)+"into any drive"
^2       Repeat 
^2          Curs Off 
^2       Until Exist("AMOS:")
^2    End If 

^1 So,  I  clear the screen, set the directory to `AMOS:', and load the
^13D extension by using the command, TD KEEP ON.

^2    Cls 0
^2    Dir$="AMOS:"
^2    Td Keep On 

^1 Now,  I need to set the directory path, BACK to my 3D work disk.  As
^1I  have  a  directory,  called  `Objects', I`ll ask AMOS to find that
^1disk, and on finding it, set the directory...

^2    If Not Exist("Df0:Objects")
^2       Centre At(,10)+"Please insert TA in drive Df0:"
^2       Repeat 
^2          Curs Off 
^2       Until Exist("Df0:Objects")
^2       Cls 0
^2    End If 

^1 This program assumes that the 3D work disk is in Df0:...

^2    Dir$="Df0:"
^2    Cls 0

^1 Now,  I  set  the  Screen Height.  In this 3D demo, I`m using a full
^1screen  value  of 256.  Usually, I use a value of 200, so as to leave
^1room for a status display.

^2    Td Screen Height 256

^1 Now,  I set the TD directory.  This is the directory, which contains
^1all of the object definitions.

^2    Td Dir "Df0:Objects/"

^1 In  this  short  demo,  I  only need to load up ONE previously saved
^1object, called `cube1'.

^2    Td Load "cube1"

^1 This  is  a  simple cube, with `TA', on all sides.  Next, I place my
^1objects  using  the  TD  OBJECT command.  Notice how I use the single
^1cube  definition  for  2  objects.   The  first  object  is placed at
^1X-co-ordinate  2000, Y-co-ordinate 2500 and a Z value of 2000.  I did
^1not  want the cube to be at any special attitude, so I just set these
^1to  0,0,0.  The second object is placed, higher up, ( Less Y value ),
^1and farther into the distance, ( Greater Z Value).

^2    Td Object 1,"cube1",2000,2500,2000,0,0,0
^2    Td Object 2,"cube1",2000,2000,6000,0,0,0

^1 Next, I want to move the viewpoint, so that when the program starts,
^1the  viewer  sees both cubes directly in front.  Remember that object
^10,  is  the  viewpoint.   And  I move it to X:2000, which is the same
^1value as my two previously defined cubes.  Y:2300, is a value sort of
^1inbetween the Y values of the 2 cubes.  Finally, the Z value is 0.

^2    Td Move 0,2000,2300,0
    
^1 Next,  I  set  some  variables  for the demo.  F1, is the Z movement
^1value  for  cube  1,  and F2 is the Z movement value for cube 2.  The
^1TIME variable, determines exactly how many times the cubes will move.

^2    F1=400
^2    F2=-400
^2    TIME=0

 ^1So, now I start up my REPEAT loop.

^2    Repeat

^1 The  following  bit  is  the  USUAL way of drawing 3D objects on the
^1screen.   First  it  clears  any previous frames, draws the new ones,
^1swaps the physical and logical screens, and finally, synchronizes it.

^2        Td Cls
^2        Td Redraw
^2        Screen Swap
^2        Wait Vbl

^1 Now,  I  want  my  first  cube  to be spinning in all 3 ways, in one
^1direction,  whilst  the  other,  doing  the  same  thing,  but in the
^1opposite  direction.   The  3 values after the object number, are the
^1attitude values of A,B and C.

^2        Td Angle Rel 1,1000,1000,1000
^2        Td Angle Rel 2,-1000,-1000,-1000

^1 Now,  I  move  the  2 cubes corresponding to what direction thay are
^1going,  so  I  use  the  values  F1,  and F2, which have been defined
^1previously.

^2        Td Move Rel 1,0,0,F1
^2        Td Move Rel 2,0,0,F2

^1 Now, I add the TIME value, by one.

^2        Add TIME,1

^1 If  the timer value has reached 13, it checks to see which direction
^1cube  1  is  going.  If it is going towards the eye, then it knows to
^1set  the other cube to go towards the viewpoint, whilst cube 1, to go
^1away.   If not, then it tells cube 1 to go towards the viewpoint, and
^1cube  2,  to  go away.  I know it sounds complicated, but it is quite
^1logical.  Finally, it sets the TIME counter back to 0.

^2        If TIME>13
^2           If F1=-400
^2                F1=400
^2                F2=-400
^2           Else 
^2                F1=-400
^2                F2=400
^2           End If 
^2           TIME=0
^2        End If 

^1 Finally,  to  add a little `Spice', to the demo, I`ve decided to put
^1in some world controls.  Basically, the following section, allows you
^1to  control  the  viewpoint`s  X  and Y values using the cursor keys.
^1(76=up, 77=down, 79=left, 78=right)

^2        If Key State(79)
^2           Td Move Rel 0,-200,0,0
^2        End If 
^2        If Key State(78)
^2           Td Move Rel 0,200,0,0
^2        End If 
^2        If Key State(76)
^2           Td Move Rel 0,0,200,0
^2        End If 
^2        If Key State(77)
^2           Td Move Rel 0,0,-200,0
^2        End If 

^1 And at last, it checks to see if QUIT=True.  As I have not put in an
^1EXIT feature on this demo, it will never be true.

^2     Until QUIT=True

^1 If  you  want  to see how this looks straight away, then load up the
^13D-Tutorial.AMOS,  program,  which  is  the  above  program,  in full
^1working form.

^4Other 3D Commands
^5+-+-+-+-+-+-+-+-+

^61.  Td Background
^7=================

^6 I found the TD BACKGROUND command very useful.  Although I have only
^6got it work on LOW RES screens.

^6 You can use it for a sky background, or even an amazing Hit tech HUD
^6display.   Believe me, if TD BACKGROUND had not been included, the 3D
^6programs would be drab and boring.

^6 Firstly,  you  have  to  note  the following point.  If you want the
^6screen  to  be displayed behind the objects, ie, like for a sky, then
^6it  must  be placed BEFORE the TD REDRAW command.  If you want to use
^6it as a HUD or a SHIPS COCKPIT picture, then use it after.

^6 It  is  perfectly  feasible to have 2 backgrounds.  I used two in my
^6space  game ZION.  screen 2 had stars on, whilst screen 3 had the HUD
^6on, I simply did it like this...

^5                 Td Cls
^5                 Td Background 2,0,0,320,200 to 0,0,0
^5                 Td Redraw
^5                 Td Background 3,0,0,320,200 to 0,0,0
^5                 Screen Swap
^5                 Wait Vbl

^6See?  It`s quite easy.

^62.  Td Range
^7============

^6 I  used  this  command,  INSTEAD of setting zones.  To me, it worked
^6better.  Just specify two objects, and you are returned with a value!
^6So if you wanted to see if missile 3, hit ship 7, you`d use something
^6like....

^5                          If Td Range(3,7)<1000
^5                             Proc WHAMBAMTHANKYAMAM
^5                          End If

^6 There are many other 3D commands.  Some of which are easy and useful
^6(  TD  FACE ), and others which are more obscure, ( TD ADVANCED ).  I
^6hope this quick tutorial has helped.

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