Re: Writing out to file : one tile at a time

On 2/06/14 12:38 AM, Michel Lerenard wrote:
> Hi,
>
> i've been there a few weeks back, the thing to understand if that the 
> FrameBuffer and the Imf image will always work as if the data buffer 
> was covering the whole image. You can't restrict a Framebuffer to work 
> on a part of the image by, for example, giving it a size.
>
> What you'll need to do to write one tile is to configure the 
> FrameBuffer with a pointer pointing to the address at which you buffer 
> would start if it was covering the whole image. The rest is all 
> pointer arithmetic.
> Typically if you're willing to write a tile that covers the region 
> 256/128 :  287/163 ( a 32*32 tile starting at 256/128 ), and your data 
> buffer contains data for the current tile only, call:
> out.setFrameBuffer (mybuffer - 256 * 128 * pixelSize , pixelSize, 
> tileWidth * pixelSize);
>
> where mybuffer is a char*, pixelSize gives the memory size of an item. 
> (char = 1, half= 2, float = 4)
Thanks Michel, now I understand why there is the subtraction going on.

Cheers

-- 
Nicholas Yue
Graphics - RenderMan, Visualization, OpenGL, HDF5
Custom Dev - C++ porting, OSX, Linux, Windows
http://au.linkedin.com/in/nicholasyue
https://vimeo.com/channels/naiadtools

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