Dolly Zoom - GameCreators Forum

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Libervurto

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Posted: 5th Feb 2010 05:28 Edited at: 10th Feb 2010 08:55

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Not entirely sure if I've already posted this.

This is my attempt to emulate the "dolly zoom" camera effect.
Dolly zoom is when the camera is moving away from the object that it is zooming in on. This makes the focal object appear to be stationary and remain the same size while objects in the background appear to move inwards.
The opposite effect can be achieved by moving the camera towards to focal object and zooming out.

I want to make a whole library of cinematic commands like this to make it easier to produce cut-scenes and what not with DBC.
[edit: removed old version, check last post.]

"With games, we create these elaborate worlds in our minds, and the computer is there to do the bookkeeping." - Will Wright

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Caleb1994

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Posted: 5th Feb 2010 05:47

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That's really cool! Good job obese! It was a little shaky the first time a ran it but after that it ran really smooth.

New Site! Check it out \/

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Libervurto

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Posted: 6th Feb 2010 07:22

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Thanks
It runs a bit shaky for me too, I don't know why.

"With games, we create these elaborate worlds in our minds, and the computer is there to do the bookkeeping." - Will Wright

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Latch

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Posted: 6th Feb 2010 08:16

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Quote: "Thanks
It runs a bit shaky for me too, I don't know why."

Keep your eye on the order of events. Do your camera movement before adjusting the field of view. I believe setting the FOV calls an automatic sync. So try:

+ Code Snippet

for dollyzoom = 0 to 100
  dec fov#,fov#/100.0
  move camera -0.1
  set camera fov fov#


  `sync
next dollyzoom

for dollyzoom = 0 to 100
  inc fov#,fov#/100.0
  move camera 0.1
  set camera fov fov#


  `sync
next dollyzoom

You also may be able to save yourself some code and use LOCK OBJECT ON for all the foreground objects that stay stationary as the scene around changes with the field of view adjustments. You shouldn't have to reposition the camera at all. The FOV will take care of the zoom and the locked objects should retain their relative positions.

Enjoy your day.

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Libervurto

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Posted: 9th Feb 2010 13:07 Edited at: 10th Feb 2010 08:56

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Quote: "Keep your eye on the order of events. Do your camera movement before adjusting the field of view. I believe setting the FOV calls an automatic sync."

Thanks Latch that makes it so much smoother

I've edited the original code.

[edit]
Turned it into a function. Well, it seems to lag slightly when I squeeze it into one function so I've also included two independent functions for zooming in and out.
[edit: removed old version]

Quote: "You also may be able to save yourself some code and use LOCK OBJECT ON for all the foreground objects that stay stationary as the scene around changes with the field of view adjustments."

The principle of this is that you can just plug it into any program and start using it. I wouldn't know how to figure out which objects needed to be locked on-the-fly.

"With games, we create these elaborate worlds in our minds, and the computer is there to do the bookkeeping." - Will Wright

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Latch

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Posted: 10th Feb 2010 04:34

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Quote: "I believe setting the FOV calls an automatic sync."

I wrote that giving you a hint to not use a sync after a SET CAMERA FOV call - at least in DBC 1.20. You'll destroy your frame rates unnecessarily:

+ Code Snippet

rem === FUNCTIONS ===
function dollyzoom(zoom)
  posneg = ((zoom>0)-(zoom<0))
  abszoom = zoom*posneg
  for i = 0 to abszoom
    move camera posneg*-0.1
    fov#(0) = fov#(0) - posneg*(fov#(0)/100.0)
    set camera fov fov#(0)

    rem get rid of the sync
    `sync
  next i
endfunction
`//

function dollyzoomin(zoom)
  for i = 0 to zoom
    move camera -0.1
    fov#(0) = fov#(0) - fov#(0)/100.0
    set camera fov fov#(0)

    rem get rid of the sync
    `sync
  next i
endfunction
`//

function dollyzoomout(zoom)
  for i = 0 to zoom
    move camera 0.1
    fov#(0) = fov#(0) + fov#(0)/100.0
    set camera fov fov#(0)

    rem get rid of the sync
    `sync
  next i
endfunction
`//

Enjoy your day.

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Libervurto

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Posted: 10th Feb 2010 08:05 Edited at: 10th Feb 2010 09:01

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oops

[edit]
I think I've cracked it in one function.
Syntax dollyzoom(distanc#,duration)
Distance is how far the camera will move each step.
Duration tells the function how many steps to run for.

The FOV is counter-balanced to keep the focal object roughly the same size in the frame.

rem Program Name: Dolly Zoom
rem Author: OBese87
rem Date: 23/10/2009
rem Edited: 10/02/2010
rem ==================
set display mode 1024,768,32
hide mouse
sync rate 60
sync on
dim fov#(0)
gosub make_scene

rem === MAIN ===
gosub setup_camera
dollyzoom(-0.08,250)
gosub setup_camera
color backdrop 0
dollyzoom(-0.5,50)
dollyzoom(0.5,50)
end

rem === SUBROUTINES ===
make_scene:
  for ob = 0 to 48
    make object cube ob+1,1
    yrotate object ob+1,45
    xrotate object ob+1,45
    position object ob+1,(ob/7)*4,(ob-(ob/7)*7)*4,0
    color object ob+1,rgb(255,0,0)
  next ob
  for ob = 0 to 48
    make object cube ob+50,1
   yrotate object ob+50,45
    xrotate object ob+50,45
    position object ob+50,(ob/7)*4,(ob-(ob/7)*7)*4,4
    color object ob+50,rgb(255,255,0)
  next ob
  for ob = 0 to 48
    make object cube ob+100,1
    yrotate object ob+100,45
    xrotate object ob+100,45
    position object ob+100,(ob/7)*4,(ob-(ob/7)*7)*4,8
    color object ob+100,rgb(0,255,0)
  next ob
return
`//

setup_camera:
  position camera 12,12,-10
  point camera 12,12,0
  fov#(0)=1.2
  set camera fov fov#(0)
return
`//

rem === FUNCTIONS ===
function dollyzoom(distance#, duration)
  fovscaler# = 10/distance#

for i = 1 to duration
   set cursor 0,0:print screen fps()
    move camera distance#
    fov#(0) = fov#(0) + fov#(0)/fovscaler#
    set camera fov fov#(0)
  next i
endfunction
`//

+ Code Snippet

rem Program Name: Dolly Zoom
rem Author: OBese87
rem Date: 23/10/2009
rem Edited: 10/02/2010
rem ==================
set display mode 1024,768,32
hide mouse
sync rate 60
sync on
dim fov#(0)
gosub make_scene

rem === MAIN ===
gosub setup_camera
dollyzoom(-0.08,250)
gosub setup_camera
color backdrop 0
dollyzoom(-0.5,50)
dollyzoom(0.5,50)
end

rem === SUBROUTINES ===
make_scene:
  for ob = 0 to 48
    make object cube ob+1,1
    yrotate object ob+1,45
    xrotate object ob+1,45
    position object ob+1,(ob/7)*4,(ob-(ob/7)*7)*4,0
    color object ob+1,rgb(255,0,0)
  next ob
  for ob = 0 to 48
    make object cube ob+50,1
   yrotate object ob+50,45
    xrotate object ob+50,45
    position object ob+50,(ob/7)*4,(ob-(ob/7)*7)*4,4
    color object ob+50,rgb(255,255,0)
  next ob
  for ob = 0 to 48
    make object cube ob+100,1
    yrotate object ob+100,45
    xrotate object ob+100,45
    position object ob+100,(ob/7)*4,(ob-(ob/7)*7)*4,8
    color object ob+100,rgb(0,255,0)
  next ob
return
`//

setup_camera:
  position camera 12,12,-10
  point camera 12,12,0
  fov#(0)=1.2
  set camera fov fov#(0)
return
`//

rem === FUNCTIONS ===
function dollyzoom(distance#, duration)
  fovscaler# = 10/distance#

  for i = 1 to duration
   set cursor 0,0:print screen fps()
    move camera distance#
    fov#(0) = fov#(0) + fov#(0)/fovscaler#
    set camera fov fov#(0)
  next i
endfunction
`//

"With games, we create these elaborate worlds in our minds, and the computer is there to do the bookkeeping." - Will Wright

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