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I'm trying to achieve a camera rig look on a motion blur shot.

But I just cant seem to get it the way i want.

Camera and Object in focus are parented to a Null that is animated along a scene.
The Object does have a lot of reflections that are supposed to be motion blurred but the Object and its contours should remain in focus



I've experimented with changing the keyframes to quicker and slower animations.
Different Shutterspeeds as well as Shutter Angle and FPS settings.

In Cinema I've tried enabling object and camera motion blur together and each on their own. Still no go

Any Ideas? Techniques or simple photographic concepts im missing?

Have you tried disabling object motion blur on the sphere only?

That won't work -- motion blur is not sophisticated enough for this scenario to work how he wants it to. Motion blur works by literally writing two positions for each vertex of a mesh in a single MXS file -- so, they basically represent where the object was at the beginning and end of the exposure.

In his scene, the only object that is moving is the sphere, so that is the only one which can possibly have two distinct locations for each mesh vertex. That he gets blur on the sphere, even though it is locked in relative position with the camera would, I suppose, be considered a bug or limitation of the system.

Joris, if you want this to work, it can, but you need to change the reference frame so that the objects you want blurred are moving -- basically, you would need to keep your camera/sphere stationary and move the whole scene in relation to them.

That's a great suggestion JD. Moving the world instead of the camera and sphere.

But also:

In his scene, the only object that is moving is the sphere, so that is the only one which can possibly have two distinct locations for each mesh vertex.

Camera based blur works, and doesn't seem to fit into your explanation of vertex based blur. How does camera blur work when there are no moving objects in the scene except camera? I guess the limitation is the interaction between camera and object blur?

Blur on the camera works with respect to the cube and its reflection, but for some reason (might be similar to the object-based mblur problem, but I'll have to double-check that there isn't something wrong with the plugin's export here) the sphere also gets blurred. If you move the scene, everything looks correct.

JDHill wrote:Joris, if you want this to work, it can, but you need to change the reference frame so that the objects you want blurred are moving -- basically, you would need to keep your camera/sphere stationary and move the whole scene in relation to them.

How can I use the IBL with this because i have different hdrs for illu/refr/refl/bg.
Inverting a sphere could work but how do i match my old ibl setup? using c4d for now.
But switching to maya and max for future setups

I'm not sure I understand the purpose of the question. IBL is always centered on the camera's location, regardless if the camera is moving or not. From an IBL standpoint, nothing changes whether you are moving the camera or moving the scene.

Yeah I know that.

What I meant is, right now for all prior render passes I was utilizing the IBL to light my scene.
Now with your Idea to move the world instead of the objects and camera this would require me to shift the IBL center which is not possible. The other option would be to create a sphere with inverted normals and assign a lambert with emitter to be able to move the sphere.

And the second option doesn't work either from what I get because as I said I have different IBL channels setup with different hdrs using individual intensities (i.e. blured low res for Illu (int. 2.0) , highres and retouched for refl and refr (int. 0.5 )and a background plate in the bg channel). AFAIK this cant be achieved by a maxwell material.

I can ditch the bg plate and comp in post, but I really do need the same refs and illumination as set up in the IBL tab to pull off the moving world thing

Now with your Idea to move the world instead of the objects and camera this would require me to shift the IBL center which is not possible.

This is the part I don't yet understand. Why, exactly, would it require that? I'm not trying to be difficult, I just do not understand why you say this, when the relationship between the projected IBL and the camera/sphere is identical between one method and the other.

If you move the scene, everything looks correct.

This is just what I thought when you said this. Because my scene consists of one emitter and ibl. Moving the scene would be moving the ibl and the emitter and leaving the cam and the sphere still.

I'll give you a better example of what effect im after:

Theres a car, a driver with sunglasses and a hdr to light the scene and provide for reflections.

The cam is located on the passenger seat looking at the driver and his glasses.
What I should see is a driver and car in focus but anything (sunglasses, mirrors etc) reflecting the ibl should have motion blur since the car is moving.

Moving the scene would be moving the ibl and the emitter and leaving the cam and the sphere still.

No, it would not.

Regarding your new scenario: if your car/driver do not move with respect to the camera, then they do not move with respect to the IBL projection sphere. You can therefore observe neither movement nor motion blur of the IBL image, neither where it is seen directly by the camera, nor where it is seen in the reflection of your driver's glasses.*

If you want a background to move past your subject, regardless of any motion blur questions, you have to put it on a billboard, and then physically move the billboard past the car/driver/camera, or vice versa. To do such a thing using IBL would require that you had a different HDRI for each frame in the animation -- each image would need to have been taken, in the real world, from different position than the previous image. That is the only way you can expect to render linear movement using IBL.

Given the original problem you posted about (i.e. the reflective sphere getting blurred even though its position is locked to that of the camera), the working solution would be to use the billboard approach, and to keep the car/driver/camera stationary while moving the billboard. Depending on the nature of the lighting, it may still be possible to use IBL for illumination; it just depends on the content of the image.


* I am referring here to linear motion only -- with camera-based blur, Maxwell will calculate motion blur for IBL, whether viewed directly or in reflections, when the camera is rotated between frames.

Here's a quick example of another method, which requires no billboard, and uses just one HDRI:




So, that is just IBL with camera blur on, and rotating the camera, rather than moving it in a line:



The nature of the setup is pretty plain in a full 360° animation, but if you were just doing a single frame or two, and you were not looking at reflections in a whole sphere, it probably would not be too apparent that you were spinning rather than moving.