Sine Wave Help

[MausBoy]

I want to use bB to move a sprite back and forth across the screen in a sine wave, does anyone have any suggestions for the best way to do it? Most old BASIC examples I've looked up don't translate to bB at all.

[+SpiceWare]

You'll have to precalculate the sine values and store them in your program.

[+batari]

You'll have to precalculate the sine values and store them in your program.

Depending on what you need, either a few data tables or individual calculations for different angles may work best. You'd want not just pre-calculated trig values, but also those values multiplied by some value (as trig functions usually are.)

 

Actual trigonometry calculations are a little too slow for any practical use in bB. I thought about making a library with a set of 8.8 trig values for 0-90 degrees and interpolate for fractional values (or not...), and this would be reasolably quick to access. The problem is usually the functions are multiplied by some value, which requires a slow 16-bit multiplication loop, and just a few of these would take up all the cycles in a frame.

[MausBoy]

Precalculated tables will be fine, not a big deal considering the limited resolution.

 

I don't think the addition of a library is necessary but then again I don't know all the ways it could be applied or how people smarter than me would use it.

[+SpiceWare]

This is how I precalculated the Fireball direction/speed tables for Medieval Mayhem. The code's for REALbasic which I used for the free 2 week demo.

 

 Const PI=3.14159
 Const PALadjust = 1.2
 Const Xadjust = 1.3
 
 dim i as integer
 
 dim x(8) as integer
 dim y(8) as integer
 dim speed as double
 
 dim NTSCxHigh as string
 dim NTSCxLow as string
 dim NTSCyHigh as string
 dim NTSCyLow as string
 
 dim PALxHigh as string
 dim PALxLow as string
 dim PALyHigh as string
 dim PALyLow as string
 
 
 for i = 0 to 8
y(i) = 256 * cos(PI/180 * i * 90 / 8)
x(i) = Xadjust * 256 * sin(PI/180 *i * 90 /8)
 next i
 x(8) = Xadjust * 256 ' adjustment, it's coming out 255
 
 ntscxhigh = "NTSCxHigh"
 ntscxlow = "NTSCxLow"
 ntscyhigh = "NTSCyHigh"
 ntscylow = "NTSCyLow"
 
 palxhigh = "PALxHigh"
 palxlow = "PALxLow"
 palyhigh = "PALyHigh"
 palylow = "PALyLow"
 
 for speed = 0 to 3.5 step .5
for i = 0 to 8 
  ntscxhigh = ntscxhigh + chr(10) + "		.byte #>" + app.formatspeed(speed * x(i)) + "; speed: " +str(speed) + " direction: " + str(i)
  ntscxlow = ntscxlow + chr(10) + "		.byte #<" + app.formatspeed(speed * x(i))+ "; speed: " +str(speed) + " direction: " + str(i)
  NTSCyhigh = NTSCyhigh + chr(10) + "		.byte #>" + app.formatspeed(speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i)
  NTSCyLow = NTSCyLow + chr(10) + "		.byte #<" + app.formatspeed(speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i)
  
  PALxhigh = PALxhigh + chr(10) + "		.byte #>" + app.formatspeed(PALadjust * speed * x(i)) + "; speed: " +str(speed) + " direction: " + str(i)
  PALxlow = PALxlow + chr(10) + "		.byte #<" + app.formatspeed(PALadjust * speed * x(i))+ "; speed: " +str(speed) + " direction: " + str(i)
  PALyhigh = PALyhigh + chr(10) + "		.byte #>" + app.formatspeed(PALadjust * speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i)
  PALyLow = PALyLow + chr(10) + "		.byte #<" + app.formatspeed(PALadjust * speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i)
next i
for i = 1 to 8
  ntscxhigh = ntscxhigh + chr(10) + "		.byte #>" + app.formatspeed(speed * x(8-i)) + "; speed: " +str(speed) + " direction: " + str(i+8)
  ntscxlow = ntscxlow + chr(10) + "		.byte #<" + app.formatspeed(speed * x(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
  NTSCyhigh = NTSCyhigh + chr(10) + "		.byte #>" + app.formatspeed(-speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
  NTSCyLow = NTSCyLow + chr(10) + "		.byte #<" + app.formatspeed(-speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
  
  PALxhigh = PALxhigh + chr(10) + "		.byte #>" + app.formatspeed(PALadjust * speed * x(8-i)) + "; speed: " +str(speed) + " direction: " + str(i+8)
  PALxlow = PALxlow + chr(10) + "		.byte #<" + app.formatspeed(PALadjust * speed * x(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
  PALyhigh = PALyhigh + chr(10) + "		.byte #>" + app.formatspeed(-PALadjust * speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
  PALyLow = PALyLow + chr(10) + "		.byte #<" + app.formatspeed(-PALadjust * speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+8)
next i
for i = 1 to 8
  ntscxhigh = ntscxhigh + chr(10) + "		.byte #>" + app.formatspeed(-speed * x(i)) + "; speed: " +str(speed) + " direction: " + str(i+16)
  ntscxlow = ntscxlow + chr(10) + "		.byte #<" + app.formatspeed(-speed * x(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
  NTSCyhigh = NTSCyhigh + chr(10) + "		.byte #>" + app.formatspeed(-speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
  NTSCyLow = NTSCyLow + chr(10) + "		.byte #<" + app.formatspeed(-speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
  
  PALxhigh = PALxhigh + chr(10) + "		.byte #>" + app.formatspeed(-PALadjust * speed * x(i)) + "; speed: " +str(speed) + " direction: " + str(i+16)
  PALxlow = PALxlow + chr(10) + "		.byte #<" + app.formatspeed(-PALadjust * speed * x(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
  PALyhigh = PALyhigh + chr(10) + "		.byte #>" + app.formatspeed(-PALadjust * speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
  PALyLow = PALyLow + chr(10) + "		.byte #<" + app.formatspeed(-PALadjust * speed * y(i))+ "; speed: " +str(speed) + " direction: " + str(i+16)
next i
for i = 1 to 7
  ntscxhigh = ntscxhigh + chr(10) + "		.byte #>" + app.formatspeed(-speed * x(8-i)) + "; speed: " +str(speed) + " direction: " + str(i+24)
  ntscxlow = ntscxlow + chr(10) + "		.byte #<" + app.formatspeed(-speed * x(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
  NTSCyhigh = NTSCyhigh + chr(10) + "		.byte #>" + app.formatspeed(speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
  NTSCyLow = NTSCyLow + chr(10) + "		.byte #<" + app.formatspeed(speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
  
  PALxhigh = PALxhigh + chr(10) + "		.byte #>" + app.formatspeed(-PALadjust * speed * x(8-i)) + "; speed: " +str(speed) + " direction: " + str(i+24)
  PALxlow = PALxlow + chr(10) + "		.byte #<" + app.formatspeed(-PALadjust * speed * x(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
  PALyhigh = PALyhigh + chr(10) + "		.byte #>" + app.formatspeed(PALadjust * speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
  PALyLow = PALyLow + chr(10) + "		.byte #<" + app.formatspeed(PALadjust * speed * y(8-i))+ "; speed: " +str(speed) + " direction: " + str(i+24)
next i
 next speed
 
 efvalues.text = ntscxhigh + chr(10) + chr(10)
 efvalues.text = efvalues.text + NTSCxLow + chr(10) + Chr(10)
 efvalues.text = efvalues.text + NTSCyhigh + chr(10) + Chr(10)
 efvalues.text = efvalues.text + NTSCylow + chr(10) + Chr(10)
 
 efvalues.text = efvalues.text + PALxhigh + chr(10) + chr(10)
 efvalues.text = efvalues.text + PALxLow + chr(10) + Chr(10)
 efvalues.text = efvalues.text + PALyhigh + chr(10) + Chr(10)
 efvalues.text = efvalues.text + PALylow + chr(10) + Chr(10)

 

The table's are quite large so I'm not going to include them here. Go hit my blog, download the source and look for the following

BALLxHigh
	.byte #>	0; speed: 0 direction: 0
	.byte #>	0; speed: 0 direction: 1
	.byte #>	0; speed: 0 direction: 2