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Hi all, I've been having an issue with motion blur in Octane for Modo it's been doing my head in all day and hoping someone can offer a solution as I'm new to Modo and this may well be something obvious I've overlooked.

I have a basic scene with just one sphere mesh, animated to move on the X axis over the space of one keyframe. Then I've set all the X keys to 'repeat' for the start and end behaviour, so it loops the motion within a single keyframe, effectively producing a 'frozen in time' kindof motion during animation. It renders as expected with the native Modo renderer but Octane is doing some really strange explainable things. The best way to see what I mean is to check my sample scene and compare the Modo renderer with the Octane one.

I took a look at your scene and wasnt seeing any motion blur in Octane at all. You must have different "default" settings, so I've had to edit your scene to make things work.

I have attached the edited scene with values to get a closer match between both renderers, but I'll explain some of the issues below.

(screenshot - left is octane, right is modo) Parts of the problem are Modo issues, while others are Octane issues.

1) Motion blur seems to work differently between Octane and Modo.
As far as I can tell, Modo's renderer can see object motion in between frames (subframes), while the octane plugin relies on the item's position being exported at exact frames then interpolates between them.

2) Modo's graph editor can cause slight rounding errors with the way you have drawn your positions, which causes problems for Octane
If you scrub your scene frame by frame and look at Modo's opengl (or the value in the mesh position X property), you'll notice after a few frames the sphere stops moving from left to right. When you set your graph to repeat, it seems to cause some problems with rounding errors at the beginning of each cycle (Modo's OpenGL doesnt know whether to draw the sphere to the left or right). Octane is matching Modo's OpenGL here and thinks the sphere is stationary, while Modo's renderer sees the subframes, therefore sees the sphere moving left to right

I made edits to the way your alternating position is done, which fixes this.

3) The other problem is your shutter speed... The Octane plugin uses milliseconds, while Modo uses 1/seconds (eg Modo's 1/48 would be approx 21ms in Octane). I tried matching this, but because Octane's motion blur is different, I had to double the shutter speed to make it look closer to Modo.

4) One more issue to be aware of is the way motion blur offset is drawn. Modo defaults to using 0 blur offset, while the Octane plugin is missing this feature (although it's available in standalone using the "before/symmetric/after" drop down list next to FPS). It doesnt seem to match perfectly between Octane and Modo anyway, but it's worth mentioning.

Hi Dino, I think Funk has accurately summed up the issues. The next release of the plugin will allow decimal point numbers for the shutter speed (allowing greater accuracy) and will also include the ability to set the Shutter Interval Alignment (as you can do in Octane Standalone).

Paul

Also, I think you need to untick Reload Mesh Each Frame When Animating on the Mesh Item in order to get object motion blur.

...and you currently need to refresh the scene after changing the shutter speed. I will fix this in the next release so a refresh is not required.

Paul