[DBP]Creating objects one ata time -- stuck!

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Reynard

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Location: CT, USA

Posted: 23rd Jan 2007 03:01

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First of all, I am new to both DarkBasic and programming in general. Second, I am not begging for the 'teh codez'. Really, I am hoping for someone to point me in the right direction so I can figure it out (mostly) for myself -- else I don't learn a whole lot.

Anyway, I have tried a number of permutations on my problem and none of them seem to work. So I will lay it out and see what you think.

My intent is to create what might be the core to a 3d space shooter. Basically, I am trying to get rotating cubes (stand ins for asteroids) to appear at random places on the screen, one at a time, and have them move "forward" toward the player. (Later, I will worry about destroying them, since I think I got a decent handle on that from Ruccus' FPS tut).

I first tried using a for...next to create the objects, then another for...next to move/rotate them. Unfortunately, it created all the objects, then moved them all in unison. I triedto add a countdown# variable to the creation loop in hopes it would 'move on' to the movement part before creating another cube. no dice.

Here's the code for what I managed to do:

sync
hide mouse
color backdrop rgb(0,40,0)

randomize timer()

countdown#=100

do

dec countdown#,1

if countdown#=0
for n=1 to 10
make object cube n,25
color object n,rgb(rnd(255),rnd(255),rnd(255))
position object n,rnd(640),rnd(480),1000
countdown#=100
next n
endif

for n=1 to 10
if object exist(n)
xrotate object n,object angle x(n)+2
yrotate object n,object angle y(n)-2.5
position object n,object position x(n),object position y(n),object position z(n)-2
endif
next n

sync
loop
[\code]

also -- I can't seem to get the cubes to appear anywhere but the upper right quadrant of the screenand I am not sure why.

Anyway -- thanks for any insights. like i said, pointing me in the right directions is as good or better than shoving code at me (though i will take that too).

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Richard Davey

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Joined: 30th Apr 2002

Location: On the Jupiter Probe

Posted: 23rd Jan 2007 03:29 Edited at: 23rd Jan 2007 03:30

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Oohhh.. SO close

The trick here is that you want to use the count-down timer, but when the count-down is reached you then want to create ONE object, and re-set the counter back up again. Then repeat.

So don't use a 'for next' loop at all - just create one single object per count-down. Here's some pseudo code to explain:

+ Code Snippet

counter = 100
rock = 1
max_rocks = 50

do

dec counter

if counter=0 and rock < max_rocks
 make object cube rock,10
 counter = 100
 inc rock
endif

for i=1 to rock
 move object i,x,y,z
 rotate object i,x,y,z
next i

endif

loop

The above is just pseudo code to give you an idea of the logic you could use. There are a hundred ways to skin this cat, but the above should get you going.

Cheers,

Rich

Heavy on the Magick

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Flashing Blade

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Location: United Kingdom

Posted: 23rd Jan 2007 14:16

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Quote: "also -- I can't seem to get the cubes to appear anywhere but the upper right quadrant of the screenand I am not sure why."

That's because:

Quote: "position object n,rnd(640),rnd(480),1000"

3D co-ordinates are not same as 2d co-ords.

0,0,0 is centre of 3D world

So you wsnt your x to be something like random from -200 to 200 (x=rnd(400)-200), your y and your z similiar. Experiment with the ranges until you get what you want.

The word "Gullible" cannot be found in any English Dictionary.

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TDK

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Posted: 23rd Jan 2007 14:56

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And, if you don't use AutoCam Off, the camera will always point at the last created object.

If you do use AutoCam Off (as you really should do), you are responsible for positioning and pointing the camera as it will by default point at 0,0,0.

As Flashing Blade says, because your random values will all be positive along the X and Z axis and your camera is pointing at 0,0,0 the objects will all be above and right of where the camera is pointing.

Use the method he suggests to distribute the object's positions randomly around 0,0,0 as it's easier than calculating the position of the middle object and pointing the camera at it.

TDK_Man

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Reynard

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Location: CT, USA

Posted: 23rd Jan 2007 23:58

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I got it to work, at least insofar as the objects appearing when and where they should. (I still need to toy with camera and object location and object speed, etc..)

However, it seems that in order to get the cubes to fly at the camera (aka the player) they stop rotating (since the only way I know how to do it is the "point object" command).

Here's the working code as it stands:

+ Code Snippet

`this is a test to create my fying cubes

`screen and camera setup
sync on
sync rate 30
set display mode 640,480,32
color backdrop rgb(0,40,0)
randomize timer()
hide mouse

`position the camera
position camera 0,0,-1000
point camera 0,0,500

`necessary variables
cube_count#=0
countdown#=100



`the loop
do

`START THE CUBE COUNTDOWN
dec countdown#,1

`create a test cube whenever you hit the spacebar
if countdown#<=0
make object cube cube_count#+1,25
inc cube_count#
color object cube_count#,rgb(255,0,0)
position object cube_count#,rnd(400)-200,rnd(400)-200,500
countdown#=100
endif

`spin and fly the test cubes
for x=1 to cube_count#
xrotate object x,object angle x(1)-5
yrotate object x,object angle y(1)-5
point object x,camera position x(),camera position y(),camera position z()
move object x,5
next x

`close the loop
sync
loop

Also: since my eventual plan is to have the player sit there and blast at flying, rotating cubes as they fly at the player, what's a good way to restrict both the spawn points of the cubes and the angle of the camera? I am thinking I want a semi-sphere "in front" of the camera. Can I use define a radius for the random spawn points? Can I just stop the mousex and mousey at +/-90 degrees?

Thanks.

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Flashing Blade

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Location: United Kingdom

Posted: 25th Jan 2007 14:25 Edited at: 25th Jan 2007 14:31

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Quote: "However, it seems that in order to get the cubes to fly at the camera (aka the player) they stop rotating (since the only way I know how to do it is the "point object" command)."

You need to have control of each astroid each with its own data.
UDT's and arrays are best. Here's a quick example of your program using a user defined type and an array to control all astroids

sync on
sync rate 30
set display mode 640,480,32
color backdrop rgb(0,40,0)
randomize timer()
hide mouse

`position the camera
position camera 0,0,-1000
point camera 0,0,500

`necessary variables
type astroidinfo
   obj
   alive
   x#
   y#
   z#
   xangle#
   yangle#
   zangle#
   speed#
endtype

dim astroid(100) as astroidinfo
countdown=timer()

`make astroids
for x=1 to 100
   astroid(x).alive=0
   astroid(x).obj=x
   make object cube x,25
   color object x,rgb(255,0,0)
   hide object x
next x

`the loop
do
   `check cube countdown
   if timer()>countdown
      makeastroid()
      countdown=timer()+1000 `milliseconds until next astroid (could make this random)
   endif
  moveastroids()
  `close the loop
  sync
loop

function makeastroid()

`find an unused astroid
   found=0
   for x=1 to 100
      if astroid(x).alive=0
         found=x
         exit `exits the for next loop - we found what we need
      endif
   next x
   if found=0
      exitfunction
   else
      `show object and give it co-ordinates
      show object astroid(found).obj
      astroid(found).x#=rnd(400)-200
      astroid(found).y#=rnd(400)-200
      astroid(found).z#=500
      `position astroid and point at camera to get angles
      position object astroid(found).obj,astroid(found).x#,astroid(found).y#,astroid(found).z#
      point object astroid(found).obj,camera position x(),camera position y(),camera position z()
      `get the angles
      astroid(found).xangle#=object angle x(astroid(found).obj)
      astroid(found).yangle#=object angle y(astroid(found).obj)
      astroid(found).zangle#=object angle z(astroid(found).obj)
      astroid(found).speed#=rnd(50)/10.0+1
      `to make sure it dosen't get used until dead and also it gets updated
      `in the moveastroids() function
      astroid(found).alive=1
   endif
endfunction

function moveastroids()

`spin and fly the test cubes
   for x=1 to 100
      if astroid(x).alive=1
         `store angles
         xtemp#=object angle x(astroid(x).obj)
         ytemp#=object angle y(astroid(x).obj)
         ztemp#=object angle z(astroid(x).obj)
         `rotate object to point on correct vector and move it
         rotate object astroid(x).obj,astroid(x).xangle#,astroid(x).yangle#,astroid(x).zangle#
         move object astroid(x).obj,astroid(x).speed#
         `restore rotation values plus speed#
         rotate object astroid(x).obj,xtemp#-astroid(x).speed#,ytemp#-astroid(x).speed#,ztemp#
      endif
   next x
endfunction

+ Code Snippet

sync on
sync rate 30
set display mode 640,480,32
color backdrop rgb(0,40,0)
randomize timer()
hide mouse

`position the camera
position camera 0,0,-1000
point camera 0,0,500

`necessary variables
type astroidinfo
   obj
   alive
   x#
   y#
   z#
   xangle#
   yangle#
   zangle#
   speed#
endtype

dim astroid(100) as astroidinfo
countdown=timer()

`make astroids
for x=1 to 100
   astroid(x).alive=0
   astroid(x).obj=x
   make object cube x,25
   color object x,rgb(255,0,0)
   hide object x
next x

`the loop
do
   `check cube countdown
   if timer()>countdown
      makeastroid()
      countdown=timer()+1000 `milliseconds until next astroid (could make this random)
   endif
  moveastroids()
  `close the loop
  sync
loop

function makeastroid()

   `find an unused astroid
   found=0
   for x=1 to 100
      if astroid(x).alive=0
         found=x
         exit `exits the for next loop - we found what we need
      endif
   next x
   if found=0
      exitfunction
   else
      `show object and give it co-ordinates
      show object astroid(found).obj
      astroid(found).x#=rnd(400)-200
      astroid(found).y#=rnd(400)-200
      astroid(found).z#=500
      `position astroid and point at camera to get angles
      position object astroid(found).obj,astroid(found).x#,astroid(found).y#,astroid(found).z#
      point object astroid(found).obj,camera position x(),camera position y(),camera position z()
      `get the angles
      astroid(found).xangle#=object angle x(astroid(found).obj)
      astroid(found).yangle#=object angle y(astroid(found).obj)
      astroid(found).zangle#=object angle z(astroid(found).obj)
      astroid(found).speed#=rnd(50)/10.0+1
      `to make sure it dosen't get used until dead and also it gets updated
      `in the moveastroids() function
      astroid(found).alive=1
   endif
endfunction

function moveastroids()

   `spin and fly the test cubes
   for x=1 to 100
      if astroid(x).alive=1
         `store angles
         xtemp#=object angle x(astroid(x).obj)
         ytemp#=object angle y(astroid(x).obj)
         ztemp#=object angle z(astroid(x).obj)
         `rotate object to point on correct vector and move it
         rotate object astroid(x).obj,astroid(x).xangle#,astroid(x).yangle#,astroid(x).zangle#
         move object astroid(x).obj,astroid(x).speed#
         `restore rotation values plus speed#
         rotate object astroid(x).obj,xtemp#-astroid(x).speed#,ytemp#-astroid(x).speed#,ztemp#
      endif
   next x
endfunction

That code is just to demonstrate how to control many different objects each with their own data.
The code cheats by using the point object and move object. Instead you are best in the function makeastroid() determing the x,y,z velocities from the x,y,z angles and speed variables. These can then be stored in the udt and used to move astroid. eg:
In the makeastroid() function:
position astroid
point astroid
use either trig or 3d vector maths to calculate velocities.
Now in moveastrroids() function add velocities to x,y,z and position object.
This method will be better in controling the astroids, eg like when two astroids collide you can calculate new velocities so they bounce away from each other.

I also altered your countdown code slightly - the method you were using would be different on deifferent speed computers.

The word "Gullible" cannot be found in any English Dictionary.

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