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*REFRESH

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  *REFRESH Colin McDonagh <colmcdonagh@btinternet.com> - 2012-03-21 21:23 +0000
    Re: *REFRESH jgharston <jgh@arcade.demon.co.uk> - 2012-03-21 15:39 -0700
      Re: *REFRESH jgharston <jgh@arcade.demon.co.uk> - 2012-03-21 15:42 -0700
        Re: *REFRESH Colin McDonagh <colmcdonagh@btinternet.com> - 2012-03-22 19:56 +0000
    Re: *REFRESH Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-22 06:42 +0100
      Re: *REFRESH Colin McDonagh <colmcdonagh@btinternet.com> - 2012-03-22 20:00 +0000

#1520 — *REFRESH

Hi one and all,

In BBC BASIC for Windows, there is a star command *REFRESH that forces a
screen refresh.

Which gives smooth animation.

Is the a RISC OS equivalent?  I'm using R6.20 on an old SA RiscPC.

Cheers

Colin.

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#1521

Colin McDonagh wrote:
> In BBC BASIC for Windows, there is a star command *REFRESH that forces a
> screen refresh, which gives smooth animation.
> Is the a RISC OS equivalent?  I'm using R6.20 on an old SA RiscPC.

There's no equivalent of *REFRESH because BB4W does't write to the
screen, it writes to a buffer which is copied to the screen at
intervals, or when *REFRESH is used. Acorn systems (usually) write
to the displayed screen.

The way to get smooth animation on Acorn systems is to set up two
screen banks, write to the non-displayed one, wait for the vertical
flyback with *FX19 or WAIT and swap the displayed and nondisplayed
banks.

JGH

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#1522

jgharston wrote:
> set up two screen banks ...

Or, an alternative would be to redirect VDU output to a sprite, wait
for flyback, and then display the sprite during the flyback interval.

JGH

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#1525

In article
<5a472327-24da-4f06-b92e-209ccb39afe8@j14g2000vbc.googlegroups.com>,
   jgharston <jgh@arcade.demon.co.uk> wrote:
> > set up two screen banks ...
Thanks JG,

This is my prog, where do I put the WAIT etc..

Cheers

Colin.



REM Simulate hybrid coupler Wave.
REM 15/03/2012
MODE 28 :REM 256-colour mode
:
ON ERROR PROCerror : END
:
REM****************************************
:
GCOL 132 :REM Sets graphic background colour to (132-128) = 4, blue.
CLG :REM Clears graphic screen to background colour
GCOL 7 :REM Sets graphic foreground colour to 7, white.
COLOUR132
REM****************************************
:
LeftEdge% = 0
RightEdge% = 1279
TopEdge% = 1023
BottomEdge% = 0
PROCbox
:
VDU 28,5,50,80,60 :REM Set up a text viewport
:
COLOUR 1
xtemp = 0
ytemp = 0
:
FOR Phase = 0 TO 359 STEP 2


loiter = INKEY(10)
CLS
PROCbox
:
FOR Angle = 0 TO 1280 STEP 1
:
Colour = 3 :REM Yellow line
PROCwave1(Colour, Angle, Phase, X, Y)
xms = X^2 + xtemp

yms = Y^2 + ytemp

NEXT Angle
xrms = SQR(xms)
yrms = SQR(yms)

PRINT TAB(50,20) "X = " xrms, TAB(50,40) " Y = " yrms
NEXT Phase
:
END
:
DEF PROCerror
REPORT
PRINT " at Line " ; ERL
ENDPROC
:
DEF PROCbox
MOVE RightEdge% , TopEdge%
REM Moves cursor to point (1279,1023), top right corner of 'standard'
screen.
:
REM Next four lines draw line around edge of 'standard' screen.
DRAW LeftEdge% , TopEdge%
DRAW LeftEdge% , BottomEdge%
DRAW RightEdge% , BottomEdge%
DRAW RightEdge% , TopEdge%
ENDPROC

DEF PROCwave1(col, angle, phi, RETURN x, RETURN y)
GCOL col  TINT 0 :REM yellow lines or blue lines
angleRad = (angle/(2*PI))/9
phaseRad = (phi/(2*PI))/9
A = 100*SIN(angleRad) :REM This is a wave, fixed to the right.
B = 100*SIN(angleRad+phaseRad) :REM This is  wave moving left.
REM phase shift one by -90 degrees
minusjA = 100*SIN(angleRad-PI/2)
REM phase shift by -90 degress
minusjB = 100*SIN(angleRad+phaseRad-PI/2)
REM To the right
PLOT &45, angle, A + 800
:
PLOT &45, angle, B + 200
GCOL col+2
REM To the left
x = 0.5*A + 0.5*minusjB
y = 0.5*B + 0.5*minusjA
REM The hybrid  wave is the sum of two above.
PLOT &45, angle, x+620
PLOT &45, angle, y+400
:
ENDPROC

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#1523

On Wed, 21 Mar 2012 21:23:56 +0000 (GMT), Colin McDonagh 
<colmcdonagh@btinternet.com> wrote:

> In BBC BASIC for Windows, there is a star command *REFRESH that 
forces a
> screen refresh.

> Which gives smooth animation.

Typically you would define two screen banks and draw into one while 
displaying the other. You can use WAIT to wait until the next screen 
scan, so swapping banks doesn't result in flicker.


Best wishes,

Rick.

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#1524

In article <almarsoft.1276196108028896754@news.orange.fr>,
   Rick Murray <heyrickmail-usenet@yahoo.co.uk> wrote:
> On Wed, 21 Mar 2012 21:23:56 +0000 (GMT), Colin McDonagh 
> <colmcdonagh@btinternet.com> wrote:

> > In BBC BASIC for Windows, there is a star command *REFRESH that 
> forces a
> > screen refresh.

> > Which gives smooth animation.

> Typically you would define two screen banks and draw into one while 
> displaying the other. You can use WAIT to wait until the next screen 
> scan, so swapping banks doesn't result in flicker.


Thanks Rick,

JG has also sugested this.

Regards

Colin.

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