Patrick Dugan wrote in message <3c34a396$1@news.povray.org>...
>I posted this before in beta test but now have more data
>
>I'm using Windows XP and creating a large BMP file.
>
>The problem regards the continue function.  I am rendering a large (10240 x
>7680) image using the switches -D for the render.  I let the render run
>all night and it creates about 600 lines.  I stop the render, reboot the
>computer (the next morning) and then start (continue with -D +c)
>the render again assuming it will continue where it left off.  Instead the
>render window shows it starting at 1 again (out of 7679) despite the fact
>that it had completed 600 lines previously.  I examined the BMP and the 600
>lines are there but povray insists on starting over at the top.
>
>Why would it do that when I have the +c switch specifed?

Normally, to figure out where a trace was interrupted, POV-Ray reads the
image file, and on the line where the file ends, POV-Ray starts tracing.
Resuming from BMP images is more difficult, since the BMP format stores the
images upside down and the whole image file must exist on the disk in order
for the first pixel of the image to be written.  I'm having trouble making
sense of the source code for reading interrupted BMP images, but it looks
like POV-Ray decides a line hasn't been rendered if the first pixel of the
line is a particular dark shade of grey and the rest of the line is black.

I strongly suggest using a different format for rendering images where you
expect the render to need to be stopped and continued.  I recommend either
the compressed or uncompressed TGA formats.

--
Mark

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