Cycles - Orthographic Size animation doesn't cause motion blur even with Motion Blur checked #84521

New Issue

Gabriel · 2021-01-08T14:28:22+01:00

Gabriel commented

2021-01-08 14:28:22 +01:00

System Information
Operating system: MacOS Mojave (10.14.6)
Graphics card: Intel Iris Pro (built-in)

I am trying to create a simple, short intro video, so at first I tried using the Workbench rendering engine, but then I wanted motion blur. So I tried using Eevee and Cycles to see how it looks with default motion blur setting.

However, once I looked at the Cycles one, I noticed this apparent bug where the zooming out/in parts (which I achieved by animating the Orthographic Size) were not blurring out because of the motion of the zoom, even though I have checked motion blur. I imagine this could have been left unchecked for a long time, seeing as both Cycles and isometric camera mode have been around quite some time I'm pretty sure.

In case further demonstrations are required than just describing this, here are the videos.

First up is the Eevee version. Notice how when it zooms out, there's significant blurring (especially near the edge). I also used a steps value of 1 in motion blur settings, so it doesn't look as smooth.

0001-0240.mp4

Now, here is the Cycles version. I'm also using OpenImageDenoise for this. Notice that it stays sharp when zooming out, and yet when anything else moves, it causes motion blur.

0001-0300.mp4

Blender Version
Broken: 2.91.0

Exact steps for others to reproduce the error

Open a new blend file.
Change the camera to Orthographic.
Add anything you want in front of the camera. Make sure this is something which can be seen once rendered in Cycles.
Animate the Orthographic Size over a section of the timeline (e.g. go to frame 1, set orthographic size however, hit I over it, go to frame 50, increase/decrease it, insert another keyframe, etc.
Move the seek head to a section between the two where the orthographic size value is moving.
Switch the rendering engine to Cycles.
Hit F12 to render just that frame.
See if it blurs out (especially around the edges of the frame).

To be very clear, this DOES NOT happen with Eevee. ONLY with Cycles. I imagine probably just that Eevee was more recent and this was taken care of when camera motion blur support was added. Since this is a simple animation, I can just use Eevee and it probably isn't gonna look that different. Especially if I try increasing that Steps thing that might smooth it out. But in a few niche cases, I can imagine how that might be quite problematic and frustrating to see that this happens. I request that the development team test this with their latest builds of their application.

**System Information** Operating system: MacOS Mojave (10.14.6) Graphics card: Intel Iris Pro (built-in) I am trying to create a simple, short intro video, so at first I tried using the Workbench rendering engine, but then I wanted motion blur. So I tried using Eevee and Cycles to see how it looks with default motion blur setting. However, once I looked at the Cycles one, I noticed this apparent bug where the zooming out/in parts (which I achieved by animating the Orthographic Size) were not blurring out because of the motion of the zoom, even though I have checked motion blur. I imagine this could have been left unchecked for a long time, seeing as both Cycles and isometric camera mode have been around quite some time I'm pretty sure. In case further demonstrations are required than just describing this, here are the videos. First up is the Eevee version. Notice how when it zooms out, there's significant blurring (especially near the edge). I also used a steps value of 1 in motion blur settings, so it doesn't look as smooth. [0001-0240.mp4](https://archive.blender.org/developer/F9555712/0001-0240.mp4) Now, here is the Cycles version. I'm also using OpenImageDenoise for this. Notice that it stays sharp when zooming out, and yet when anything else moves, it causes motion blur. [0001-0300.mp4](https://archive.blender.org/developer/F9555719/0001-0300.mp4) **Blender Version** Broken: 2.91.0 **Exact steps for others to reproduce the error** 1. Open a new blend file. 2. Change the camera to Orthographic. 3. Add anything you want in front of the camera. Make sure this is something which can be seen once rendered in Cycles. 4. Animate the Orthographic Size over a section of the timeline (e.g. go to frame 1, set orthographic size however, hit I over it, go to frame 50, increase/decrease it, insert another keyframe, etc. 5. Move the seek head to a section between the two where the orthographic size value is moving. 6. Switch the rendering engine to Cycles. 7. Hit F12 to render just that frame. 8. See if it blurs out (especially around the edges of the frame). To be very clear, this DOES NOT happen with Eevee. ONLY with Cycles. I imagine probably just that Eevee was more recent and this was taken care of when camera motion blur support was added. Since this is a simple animation, I can just use Eevee and it probably isn't gonna look that different. Especially if I try increasing that Steps thing that might smooth it out. But in a few niche cases, I can imagine how that might be quite problematic and frustrating to see that this happens. I request that the development team test this with their latest builds of their application.

Gabriel commented

2021-01-08 14:28:22 +01:00

Added subscriber: @CuriousHobbyist

Robert Guetzkow commented

2021-01-08 14:33:14 +01:00

Added subscribers: @Sergey, @brecht, @rjg

Robert Guetzkow commented

2021-01-08 14:33:14 +01:00

Based on #46523 and dc3563ff48 this is a known limitation that hasn't changed as far as I'm aware.

@Sergey @brecht I assume this is still the case and the ticket can be merged into #46523?

Based on #46523 and dc3563ff48 this is a known limitation that hasn't changed as far as I'm aware. @Sergey @brecht I assume this is still the case and the ticket can be merged into #46523?

Gabriel commented

2021-01-08 16:15:39 +01:00

OK. Interesting. But what I'm wondering is if this could be fixed. And why Eevee doesn't have this same problem. If it could be fixed with Cycles, I would urge the development team to try to fix it if it's been there for that long, like definitely at least since 2015 if not longer.

From my understanding the way this works is it samples the image with the moving objects at different points (if motion blur is enabled for them of course). Wouldn't it be the same sort of process to apply to changing/animating the orthographic size? I don't understand why that would be relatively hard to program.

OK. Interesting. But what I'm wondering is if this could be fixed. And why Eevee doesn't have this same problem. If it could be fixed with Cycles, I would urge the development team to try to fix it if it's been there for that long, like definitely at least since 2015 if not longer. From my understanding the way this works is it samples the image with the moving objects at different points (if motion blur is enabled for them of course). Wouldn't it be the same sort of process to apply to changing/animating the orthographic size? I don't understand why that would be relatively hard to program.

Philipp Oeser commented

2021-02-09 18:28:55 +01:00

Added subscribers: @Blendify, @lichtwerk

Philipp Oeser commented

2021-02-09 18:28:55 +01:00

@Blendify: maybe this could be added to https://docs.blender.org/manual/en/dev/render/cycles/render_settings/motion_blur.html?

It is not a bug though (just not implemented) and since has to be closed I am afraid.

@Blendify: maybe this could be added to https://docs.blender.org/manual/en/dev/render/cycles/render_settings/motion_blur.html? It is not a bug though (just not implemented) and since has to be closed I am afraid.

Philipp Oeser commented

2021-02-09 18:29:03 +01:00

Closed as duplicate of #46523

Philipp Oeser closed this issue

2021-02-09 18:29:03 +01:00

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Cycles - Orthographic Size animation doesn't cause motion blur even with Motion Blur checked #84521