' Desired approximate frames per second (but will be lower on slower computers)
fpsTarget = 20
' Determine speed of computer
CalibrateDelay()
' Set up graphics window
GraphicsWindow.BackgroundColor = "DarkGreen"
GraphicsWindow.Title = ""
GraphicsWindow.Show()
GraphicsWindow.Width = windowWidth
GraphicsWindow.Height = windowHeight
' Center it on desktop
GraphicsWindow.Left = Desktop.Width / 2 - GraphicsWindow.Width / 2
GraphicsWindow.Top = Desktop.Height / 2 - GraphicsWindow.Height / 2
' Show a dot in center of display for mouse reference when 'steering' camera
GraphicsWindow.PenColor = "Yellow"
centerShape = Shapes.AddEllipse(4, 4)
Shapes.Move(centerShape, windowWidth * 0.5 - 2, windowHeight * 0.5 - 2)
InitViewer()
InitScenery()
' The game loop
MainLoop()
' Exit game
Program.End()
' Main game routine
Sub MainLoop
' Game control variables (not set in this example)
play = true
pause = false
' Loop forever while playing
While(play = true)
' Do work if not paused
If (pause = false) Then
Move()
UpdateScreen()
' Smooth estimate of time elapsed between frames
tNow = Clock.Millisecond
dT = tNow - tLast
tLast = tNow
' Handle millisecond rollover at 1 second marks
If (dT < 0) Then
dT = dT + 1000
EndIf
k = 0.1 ' 1 = no smoothing, values less than 1 smooths. 0.1 default
dTLossy = dTLossy * (1 - k) + dT * k
' Figure out how long we need to wait to achieve desired average frame rate
waitLoops = 1000 / fpsTarget - dTLossy ' Milliseconds of time to kill
waitLoops = waitLoops * loopsPerMilliSec
For i = 1 to waitLoops
i = i
EndFor
' Show FPS
'dText = 1000/dTLossy
'Debug()
EndIf
EndWhile
EndSub
' Determine how many For loops we can do in a millisecond, used for calibrated delays
Sub CalibrateDelay
Program.Delay(200) ' Let software 'settle' on load
' Figure out dummy wait loops per millisecond
' Used instead of Program.Delay()'s coarse resolution of 16 ms
tLast = Clock.Millisecond
waitLoops = 20000
For i = 1 to waitLoops
i = i
EndFor
tNow = Clock.Millisecond
dT = tNow - tLast
If (dT < 0) Then
dT = dT + 1000
EndIf
loopsPerMilliSec = 20000 / dT
EndSub
' Do the motion of the camera/plane/tank/person etc.
Sub Move
' Determine view attitude from mouse
pitch = Math.Pi * (GraphicsWindow.MouseY - windowHeight * 0.5) / windowHeight
roll = 2 * Math.Pi * (GraphicsWindow.MouseX - windowWidth * 0.5) / windowWidth
' Heading, if both mouse buttons pressed, reset heading to zero (north)
If Mouse.IsLeftButtonDown Then
If Mouse.IsRightButtonDown Then
heading = 0
Else
heading = heading - 0.04
EndIf
ElseIf Mouse.IsRightButtonDown Then
heading = heading + 0.04
EndIf
If heading > 2 * Math.Pi Then
heading = 0
ElseIf heading < 0 Then
heading = 2 * Math.Pi
EndIf
' Update all graphics resulting from motion/view updates
Sub UpdateScreen
' Do this once per frame
SetCamera()
' Translate all objects to graphics window
For i = 1 to objects
' Copy point for input to TransformPoint subroutine
x = objX[i]
y = objY[i]
z = objZ[i]
' Position/rotate point to display surface
TransformPoint()
' Note: shouldn't really plot anything outside the graphics window area (<0 or >width or height)
' but not checked here
' Erase old point, only plot if in front of camera (not behind!)
If (objZold[i] > 0) Then
GraphicsWindow.BrushColor = "DarkGreen"
GraphicsWindow.FillEllipse(objXold[i]-3, objYold[i]-3, 6, 6)
EndIf
' Draw new point
If (z > 0) Then
' Draw special colors for north/east points so we can make sure all's well
If i = 27 Then ' north point
GraphicsWindow.BrushColor = "White"
ElseIf i = 41 Then ' east point
GraphicsWindow.BrushColor = "Blue"
Else
GraphicsWindow.BrushColor = "Red"
EndIf
GraphicsWindow.FillEllipse(x-2, y-2, 4, 4)
EndIf
' Save point for erasure next frame
objXold[i] = x
objYold[i] = y
objZold[i] = z
EndFor
EndSub
' Initialize our variables
Sub InitViewer
' Viewer attitude, Euler order is heading-pitch-roll
heading = 0
pitch = 0
roll = 0
' Viewer position - any linear units you want (meters, feet, angstroms), just keep everything in same units!
pX = 0 ' +East
pY = -300 ' +North
pZ = 60 ' +up
EndSub
' Initialize the scenery
Sub InitScenery
method = 2 ' 1 or 2 for demo
If method = 1 Then
' Individually create points on display
objects = 4
objX[1] = 30
objY[1] = 150
objZ[1] = 0
objX[2] = 30
objY[2] = -150
objZ[2] = 0
objX[3] = -30
objY[3] = -150
objZ[3] = 0
objX[4] = -30
objY[4] = 150
objZ[4] = 0
ElseIf method = 2 Then
' Draw rectangular grid, ground level, long side runs north-south
objects = 0
z = 0
For x = -200 To 200 Step 100
For y = -400 To 400 Step 100
objX[objects+1] = x
objY[objects+1] = y
objZ[objects+1] = z
objects = objects + 1
'TextWindow.WriteLine(objects + ": " + x + ", " + y + ", " + z)
EndFor
EndFor
EndIf
EndSub
' Set camera view (done once/frame)
' This would normally speed up processing a group TransformPoint calls,
' but wasn't really measureable in Small Basic
Sub SetCamera
cosHeading = Math.Cos(heading)
sinHeading = Math.Sin(heading)
cosPitch = Math.Cos(pitch)
sinPitch = Math.Sin(pitch)
cosRoll = Math.Cos(roll)
sinRoll = Math.Sin(roll)
EndSub
' Transform point in space x,y,z to screen coordinates x,y
' Input uses a right-handed coordinate system (+x east, +y north, +z up).
' Positive heading is viewer rotating clockwise when looking down to ground, relative from North. Range: 0 to 2PI (0-360 degrees)
' Positive pitch is viewer 'nose' up. Range: +/- PI/2 (+/- 90 degrees)
' Positive roll is viewer rolled clockwise from vertical as observed from rear cockpit view. Range: +/- PI (-180 to +180 degrees)
'
' modified from http://gamecode.tripod.com/tut/tut03.htm (note bug: z=twice on yaw rotation)
Sub TransformPoint
' Shift point in space to point relative to camera position
x2 = x - Px
y2 = y - Py
z2 = z - Pz
' Now do rotations about camera point, Euler order is heading - pitch - roll
' Heading rotation
x = -y2 * sinHeading + x2 * cosHeading
y = y2 * cosHeading + x2 * sinHeading
z = z2
' Pitch
x2 = x
y2 = z * sinPitch + y * cosPitch
z2 = z * cosPitch - y * sinPitch
' Roll
x = -z2 * sinRoll + x2 * cosRoll
y = z2 * cosRoll + x2 * sinRoll
z = y2
' Check to see if point is very close to camera,
' if so put it behind the camera (so not shown and doesn't cause divide by zero below)
If Math.Abs(z) < .01 Then
z = -0.01
EndIf
' Perspective project onto screen & center it in graphics window
fov = windowWidth * 0.25 ' relative field of view - adjust 0.25 to what you like
x = x * fov / z + windowWidth * 0.5
y = -y * fov / z + windowHeight * 0.5 ' Negate Y since opposite that of the graphics window sense
EndSub
' Fill in dText variable and call this to print it on display for debugging code
sub Debug
' Erase old printout
GraphicsWindow.PenColor = "black"
GraphicsWindow.BrushColor = "black"
GraphicsWindow.FillRectangle (0, 30, 500, 30)
Program Listing: QSW885