Render only bounding box

Hi guys,
is there a way to limit Blender to render only to the bounding box area, but still save the rendered image in correct width and height (just setting the pixels outside the bounding box to transparent) ?

It would be a huge timesaver for me.


Moved from “General Forums” > “Blender and CG Discussions” to “Support > Lighting and Rendering”

The feature you’re likely looking for is Render Border

If I’m remembering correctly, using a Ctrl + B bounding box in Camera View will do what you’re asking when you do a full render. Is it not doing that for you?

Thank you so much for the quick replies.
I’ve checked out the “Border” function, but it only renders within a fixed border - which is okay for stills. For animations I was looking for a border function that changes its coordinates and size (as a bounding box) as the chosen object moves inside the frame?

Thanks for quick replies, but the border-function is only for a static position. I’m rendering animations and most pixels of each frame are actually empty. So I was looking for a function to render only the inside of a bounding box of a object, and then set the rest of the pixels in the frame as transparent? It would be a huge time-saver when rendering.

Yes, it’s bizarre that this isn’t built into Blender, it’s so frustrating to see Cycle spend ages rendering portion are the screen that are 100% empty.

I’m using Blender for m0tion graphics and i need to render multiple small objects that move around the screen. There must be a way to make the render track the object and not render the empty space while keeping the output frame to the same dimensions for all frames?!

@Daz_Harris A partial workaround would be to add a new view layer, and have only the object you want rendered visible on that layer, with the background set to transparent (Render Properties->Film->Transparent).

This is a partial workaround as Cycles will still search the transparent areas and will quickly move on when it finds nothing is there. Still not as fast as an animated render region would be since the areas outside the region would be completely ignored.

Also consider how realistic you need the lighting to be. If you are rendering just the moving object without the rest of the scene, you won’t recieve the light that would have bounced off other objects before hitting the one you are rendering.

Thanks EAW, i’m actually doing some motion graphics stuff so only have emitted light, no lights or reflections.

Since i wrote my post i discoved the add-on " Animated Render Border" which does exactly what i need, you can keyframe the bounding box size and position to track your object. I’m using motion blur with very long shutter times, so need to tweak this (although the add-on can automatically track your object which would be the easier method if you aren’t using motion blur or particles or whatever).

I’m testing it now and am managing to render a small object moving around the screen approx. 50 times faster than without the addon.

And it saves a huge amount of disk space!

Fingers crossed it stays stable and the developer keeps supporting it!

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