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Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
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Render region issue

Message 1 of 5
496 Views, 4 Replies

Render region issue

Hello, often, after a render has been completed, I need to make a quick re-render of a small portion of the scene to fix some minor problem, maybe a material that I'd forgotten to change. With the standard renderer I could do this by dragging the C4D IRR rectangle over the area, and copy the region via the render settings. However, with the renderer set to Arnold, this tool no longer works properly, especially with heavy scenes (causes C4D to freeze), and I must use the Arnold IPR render region tool instead. But in order to use this tool, I must first make a preview render with the IPR, which can take up to 2 minutes, making this option infeasible.

Ideally, Arnold would provide a simple tool, a render region toggle button, which can replace the existing C4D IRR button. When the user presses this button, a rectangle appears in the C4D editor window which the user can change the shape and position. When the user is happy with the position of the rectangle, they can click a link beneath the rectangle which says "Copy to RR" to copy the region to the render settings (or click the Copy from IRR button in the render settings if it's possible), and the toggle button will uncheck itself and the rectangle will disappear. Essentially, this would function almost exactly the same the existing C4D IRR button, but without any automatic rendering in the rectangle. The only purpose of this tool would be to quickly generate a render region from the C4D editor window. This will greatly improve the usability of Arnold. Thank you.

Message 2 of 5
in reply to: jrw2

Good one, thanks for the request. One option would be to completely ignore IRR when rendering with Arnold (it's not supported anyway), so you could use this tool as you would normally. If that's not feasible I can implement a custom tool for this as you described.

Message 3 of 5
in reply to: peter.horvath6V6K3

Yes, I can use the IRR to copy the render region even when using Arnold, but for heavy scenes (lots of geometry, textures and displacement) the IRR causes C4D to completely freeze up. A tool for this would be most welcome.

Message 4 of 5
in reply to: jrw2

+1 for this. I'm in this exact situation now where I need to re-render a small portion.


My workaround is to:

  • switch to standard renderer
  • open up IRR
  • Set position of IRR (this becomes very difficult to do accurately, as all Arnold materials turn black in the viewport and you cant see what you're covering)
  • Close IRR
  • Open render settings and copy from IRR
  • Render

It works, kind of, as long as your guess of the IRR position is good.


jrw2's suggestion would be an absolute dream, if this could be implemented!




Message 5 of 5
in reply to: jrw2

May I ask again why you can not use the render region in the IPR window for this? The original comment says, that you have to wait minutes for the IPR to render. I can see that could be inconvenient, but the first iteration in the IPR window should be quick (with -3 AA samples), and probably good enough to specify the region?


The plugin also has a feature to re-render selected objects only and update a previously rendered image, specifically for this use-case. Is that not sufficient? It has a limitation though to ignore secondary rays, so the object won't be updated in reflection and transmission. 

// Peter Horvath
// C4DtoA developer

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