Motionblur backward sampling?

[kimgar]

uhm, i'm using SP2 and struggling with physical camera and motion blur, for testing purposes i just made a simple scene where a sphere moves from left to right, and i get this result :



why does the sphere insist on looking like it is moving from right to left?

i've tried all vray camera settings like duration, interval center, bias etc. no values have any impact on the render whatsoever. the only parameter that does anything is geometry samples.

in the end i need to do a pflow animation where particles are moving both towards and away from a moving camera, and the result just looks very wrong.

i must be missing something vital, could someone fill me in?

[kimgar]

ah of course! - it is too early in the morning, sorry

i've got 1 sec shutter so i'm of course sampling 25 frames ahead of rendered frame *blush*

in addition, the sphere motion was not linear, hence the illusion of the sphere moving the wrong way...

the real question is; can i force the sampling to happen on previous frames? i was kind of hoping that duration -25, bias, or interval center could help me out, but nothing really happens when tweaking those settings....

[vlado]

If you are using the physical camera, then switch to a Movie camera and then you can use the shutter offset parameter.

Otherwise, for a regular camera, use the interval center option (you can use maxscript to change this beyond the UI locked values).

Best regards,
Vlado

[kimgar]

ah, thanks vlado, i was just testing out latencies and offsets with different camera types, and i do get a lot more control, although i think i will have to look into ghost trails or something since what i am looking for is too far from physically correct (i think)...

thanks for all help!