Motion blur bug with skeletal meshes when using planar reflections

anonymous_user_fbe2d247 · June 3, 2016, 5:09pm

Topic says it all. Character motion blur is out of control if planar reflection is used. We have Use accurate motion vectors on.

anonymous_user_6e7b421a · June 3, 2016, 6:57pm

Hey Kalle_H,

Can you provide me the steps you are taking for this to occur in a blank template project?

Are you using the default values for Motion Blur in your post process settings?

We have Use accurate motion vectors on.

Are you referring to the Use Accurate Velocities for Vertex Deformation?

Thank you,

anonymous_user_fbe2d247 · June 3, 2016, 8:01pm

This is how bug looks. I managed to make simple test case using 3rd person template project. I added single planar reflection capture. Then I changed two project settings. “Use Accurate Velocities for Vertex Deformation” and I enabled Clip plane usage.
Link for test project. http://s000.tinyupload.com/?file_id=00165948269558538051

anonymous_user_6e7b421a · June 3, 2016, 8:40pm

I just tested this in your project and was able to see the issue. With that said, I tested in a new blank Third Person Template project and the issue doe not appear at all. Please test this once more creating a new blank project from scratch, and without changing any other settings aside from the two you mentioned. It looks like you might have modified the material on the ground within the test project you provided.

Thank you,

anonymous_user_fbe2d247 · June 3, 2016, 9:20pm

I downloaded template samples just for that test case. I didn’t even open the material editor. Did you remember to add planar reflection actor? Bug does not happen without planar reflections being active.

anonymous_user_fbe2d247 · June 6, 2016, 6:07pm

Any updates? Do you need more info?

anonymous_user_6e7b421a · June 7, 2016, 7:11pm

I am still not seeing the extreme blur when I recreate this from scratch in the Third Person Template Project. Below are the steps I followed in order to set up the test.

Create new Third Person BP project.
Add Planar Reflection actor to scene. (use image as reference for how to place)
Enabled the ‘Support global Clip plane for Planar Reflections’
Restarted project.
Press PIE.

Planar Reflections Actor Placement

Let me know if you have further questions or need additional assistance.

Cheers,

anonymous_user_fbe2d247 · June 7, 2016, 8:40pm

“Use Accurate Velocities for Vertex Deformation” is also needed for bug to appear.

3DMoss · June 7, 2016, 10:06pm

I’m experiencing this bug in my project as well.

anonymous_user_6e7b421a · June 8, 2016, 2:14pm

Hey Kalle_H,

Thanks for the clarification in my steps, as I was able to reproduce the issue on my end. I appreciate your patience while I got this tested and confirmed. Below is a link to the report on our public tracker.

UE-31768

Once the issue has been addressed by our developers and a fix has been made, it will be added to the list of fixed issues for an upcoming major engine release or hotfix. If you have further questions or comments please let me know.

Thank you,

3DMoss · March 8, 2017, 7:24am

This is still an issue in 4.15. How are people working around this? It seems important enough to have been addressed by now. I guess not many are using planar reflections?

anonymous_user_c94f194d · March 8, 2017, 10:50am

We just disabled “Use accurate Velocities for Vertex Deformation” and temporalAA. It’s not shippable quality but we can work with it now.