RSMB + Vray...

[stilgarna]

I wish for a velocity element compatibl with reelsmart motion blur pro... or a tool to convert vray velocity into rsmb velocity...

Best regards...

[jonnybefree]

+1

[vlado]

Well, from what I can see, the V-Ray velocity channel should mostly work (you will need to flip the Y direction though, as noted in the RSMB docs). I'll try to do some tests here as well.

Best regards,
Vlado

[stilgarna]

Well, from what I can see, the V-Ray velocity channel should mostly work (you will need to flip the Y direction though, as noted in the RSMB docs). I'll try to do some tests here as well.

Best regards,
Vlado

After you tested it, can you post the way to use it ?

Best regards ...

[vlado]

There is nothing really specific about this; it's the same approach as you would take with the scanline renderer:

(*) Add the VRayVelocity render element;
(*) Go to some frame of the animation where objects are moving fast;
(*) Render the frame;
(*) Go to the VRayVelocity render element and check out the "max velocity in last frame" value. Suppose this is, let's say 36.67;
(*) Set the "max velocity" parameter of the VRayVelocity element to something just above this value, e.g. 40.0 and note this value (it is the "Max. Displace" value that you must enter into RSMB).
(*) Render the scene along with the velocity render element.

In your compositing application (I used Premier evaluation for this):

(*) Load the rgb and velocity sequences and apply a RSMB Vectors effect to the RGB sequence;
(*) In the RSMB Vectors parameters, select the "Motion vector" source to be the velocity sequence;
(*) Set "Max. Displace" to be equal to the "max velocity" parameter in the VRayVelocity render element parameters (e.g. 40.0);
(*) You may need to set the "Vec Scale Y" parameter to -1 as noted in the RSMB manual;
(*) Adjust "Blur Amt" as you wish (for example, 1.0 for motion blur duration of 1 frame);

Ideally this should be all. It seemed to work fine on two scenes that I tested.

Best regards,
Vlado

[vlado]

Here is also a quick sequence that I did in this way (13 MB):

http://www.spot3d.com/vray/images/st.../rsmb_vray.avi

(There is no AA since I forgot to turn it on )

Best regards,
Vlado

[stilgarna]

Many many thanks....


You're an half god ( like hercules or something... )


I'll try all this stuff tonight...


Best regards.

[Morbid Angel]

I must say that I have done comparisons about 3 years ago. Things have changed since then
However Vlado, looking at your test the rsmb result is not entirely correct. I need to do more tests, when we get this in vray for maya

[percydaman]

ya its not perfect, I found a frame where the monkeys fist is horribly blurred, but I couldn't really find it in the playing animation. I also did a test awhile back. It was better then rsmb without motion channel, but by no means as good as 3d moblur.

[Morbid Angel]

we have used mental rays motion vectors extensivly through out...Its by no means comparable to 3d motion blur in many cases. Objects behind transparent/refractive objects. Cast shadows...and many others. However, in typical conditions you can get a close match. Though, it may become an issue, if for example you have to deal with something like 300 passes, as I had once. Motion vectoring all of them was a nightmare for compositing.

[DaForce]

Yeah it almost looks like the MB is on..off..on..off..on..off

at Vlado forgetting AA.. not sure why but I found that quite amusing... could be my lack of sleep tho. hehe

[vlado]

Yeah it almost looks like the MB is on..off..on..off..on..off

This is because 2d motion blur cannot get you the same sense of motion continuity as true 3d motion blur where sudden changes of velocity happen.

For example, consider the frames where the arm of the ape is away from the chest, but is just starting to go towards it. At that time, the istantaneous velocity of the arm is zero, as it has just finished moving away, but has not started moving towards the chest yet - and consequently, you will get no 2d motion blur for the arm in this frame.

However, 3d motion blur considers the position of the arm in two consequtive frames, regardless of its instantaneous velocity in these frames. So, it will consider one position where the arm is away, and the next frame where is it closer to the chest. There will be a smooth motion blur between the two positions.

Best regards,
Vlado

[Morbid Angel]

Yeah it almost looks like the MB is on..off..on..off..on..off

This is because 2d motion blur cannot get you the same sense of motion continuity as true 3d motion blur where sudden changes of velocity happen.

For example, consider the frames where the arm of the ape is away from the chest, but is just starting to go towards it. At that time, the istantaneous velocity of the arm is zero, as it has just finished moving away, but has not started moving towards the chest yet - and consequently, you will get no 2d motion blur for the arm in this frame.

However, 3d motion blur considers the position of the arm in two consequtive frames, regardless of its instantaneous velocity in these frames. So, it will consider one position where the arm is away, and the next frame where is it closer to the chest. There will be a smooth motion blur between the two positions.

Best regards,
Vlado

to me the motion blur looks incorrect in another form. I will do some tests to demonstrate later.

[Guest]

There is nothing really specific about this; it's the same approach as you would take with the scanline renderer:

(*) Add the VRayVelocity render element;
(*) Go to some frame of the animation where objects are moving fast;
(*) Render the frame;
(*) Go to the VRayVelocity render element and check out the "max velocity in last frame" value. Suppose this is, let's say 36.67;
(*) Set the "max velocity" parameter of the VRayVelocity element to something just above this value, e.g. 40.0 and note this value (it is the "Max. Displace" value that you must enter into RSMB).
(*) Render the scene along with the velocity render element.

In your compositing application (I used Premier evaluation for this):

(*) Load the rgb and velocity sequences and apply a RSMB Vectors effect to the RGB sequence;
(*) In the RSMB Vectors parameters, select the "Motion vector" source to be the velocity sequence;
(*) Set "Max. Displace" to be equal to the "max velocity" parameter in the VRayVelocity render element parameters (e.g. 40.0);
(*) You may need to set the "Vec Scale Y" parameter to -1 as noted in the RSMB manual;
(*) Adjust "Blur Amt" as you wish (for example, 1.0 for motion blur duration of 1 frame);

Ideally this should be all. It seemed to work fine on two scenes that I tested.

Best regards,
Vlado

Resurrecting an old thread but I am having a play with the velocity pass and I am not sure if I should increase the max velocity if I am rendering as EXR? Should I leave it at 1 or change it to my max velocity in last frame? It looks correct in AE leaving it at 1 i.e the blur only going in the direction the object is spinning which is Z axis, compared to changing it to match the max velocity in last frame but wanted to be sure I was doing it right.

Max velocity set to match.

Max velocity remains at 1.

[Guest]

I have noticed when leaving the max velocity at 1, the middle has some sort of pinching in the blur. Where it has that divide.