I’ve been working with compositing nodes and I recently thought of a good method for solving a problem I have. I had never used the “file output” node before. But I thought this would be the perfect time to try it.
The problem: I have an animation of crumbling bricks. I am seeking to add dust after the fact. I am not using particles. I am only adding smoke in post.
The solution: In the compositor, I added two image inputs. They are both from the same animation, just offset by a frame. So at any give point I am comparing frames 1 and 2, 4 and 5, 11 and 12, etc. I subtract one frame from the other and then boost the difference so I have a matte of what changed from one frame to the next. All I have to do now is change the color of the matte to my dust color, blur it, and lay it over the top of my animation. This works alright but I want the dust to linger. It shouldn’t be there one frame and be gone the next. To solve this problem I decided to use the file output. I would start with a single image and modify it for each frame, then save it back - basically using the image on disk as an accumulation buffer. This method would save a lot of time vs. writing imagemagik scripts by hand. So I got everything set up and…
It doesn’t work.
The file output node increments the file it saves to. So even though I typed in “dust.png” as my output file, it saves to “dust017.png.” So, is there a way to force this node to save the same file no matter what? If not, could that be implemented? Just a toggle to save to the same file instead of adding the frame number?