VFB, Vrimg and saving render channels

[tricky]

We do pretty high resolution renders with quite a few render elements channels. Typically, we have rendered to a vrimg file (with preview ticked) to reduce the amount of RAM needed to display the frame buffers. Not doing this has often resulted in a crash.

However, I would like to continue to work like this, but also save out any render elements out as split render channels. When I uncheck 'Render to memory frame buffer' the 'Split render channels' greys out.

Is it not possible to render a vrimg file without the memory frame buffer, yet automatically save out any render elements used?

[sv]

you can extract the channels using the exrconverter. use the -info command to display what channels are embedded - the vrimg format will store the channels as well.

[tricky]

I know about that, but I am trying to do this automatically at render time. vrimg2exr is a bit long-winded.

Anyone?

[m_hinks]

You could save to .exr instead, then extract the elements in CS3 with ProExr. The plugin is quite slow to process the first at first, but once open you have all setting there to use.

[tricky]

Vlado - any comments on this?

Essentially, when I render at large resolutions with many multimatte render elements, I save to a vrimg file (with 'Generate preview' ticked) and uncheck 'Render to memory frame buffer' to prevent crashes from my system running out of RAM.

When I do this, I can't get the render elements to automatically save out, and instead I have to use the vrimg2exr utility on each and every multimatte render element. This is time consuming.

Why is this the case? Why can I not have the channels automatically saved out on render completion?

[vlado]

For the Split channels option, V-Ray uses the 3ds Max bitmap saver. For this to be used, the entire image to be saved needs to be in memory. However, if you have un-checked the "Render to memory frame buffer" option, V-Ray does not keep the entire images, instead it writes the buckets directly to disk as they are rendered. Since the entire images are not available, there is no way to save them out with a 3ds Max saver.

I suppose that one can add a post-render-frame callback that would automatically call vrimg2exr to extract the channels though.

Best regards,
Vlado

[tricky]

That would be ideal. Its a time-consuming process to extract them all manually.