New WritePixel() or TPixMap Bug?

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Midimaster

(Posted 2009) [#1]

I am writing a fast oval algorith and I decided to do it this way:

Function AuchOval(B%,H%)
    Local Mal:TPixmap=CreatePixmap(300,200,PF_RGBA8888)
 	For Local I#=180 To 270 Step .1
        WritePixel Mal,B+Sin(i)*B+1,H+Cos(i)*H+1,$ffffffff
	Next
   Local Bild:Timage=LoadImage(Mal)
   DrawImage Bild,0,100
End Function

Function only paints a quarter of the oval. Later I will copy the rest while changing "SetScale".

Ok, the function seems to work perfect. but to test the performance I put it into this surrounding:

SuperStrict
Graphics 400,300
Global Test%
Repeat
	Cls
	Test=Test+1
	DrawText "Round"+test ,20,20 
	DrawText "painiting 10 ovals:",20,40 
	For Local i%=1 To 10
		AuchOval 200,100
	Next
	Flip
	Delay 100
Until KeyHit(key_escape)

Now something strange happens: In the first seconds it works as expected. But after a certain number of paintings, the POINTER to Map:TPixMap seems to have the wrong adress.

see this picture:

If you cannot see the problem on your computer, change the 10 to 100 in:

For Local i%=1 To 10

degac

(Posted 2009) [#2]

To fix this behaviour use ClearPixel after creating the Pixmap.

In any case after 70/75 round my computer starts to 'get very slow'...

Midimaster

(Posted 2009) [#3]

Yes, that the second behavoir I recognized too. The larger the pixmap the earlier the problem occurs.

Can it be because of a memory problem or grafic card problem?

Thank you for the advise. I will test it and find out what the command is good for. Is this a workaround or the normal procedure of creating PIXMAPS? Isn't the pixmap created new each time I call the CREATEPIXMAP?

degac

(Posted 2009) [#4]

Thank you for the advise. I will test it and find out what the command is good for. Is this a workaround or the normal procedure of creating PIXMAPS? Isn't the pixmap created new each time I call the CREATEPIXMAP?

I think this can be considered as 'normal' because the in-line help refers to ClearPixel...from the docs

Note that the newly created pixmap will contain random data. ClearPixels can be used to set all pixels to a known value prior to use.

Probably there's no guarantee the ram-bank alloced for the Pixmap is 'empty'.