Although generally recognized as a render intensive process in scene or in camera 3D motion blur can sometimes be the only way to create a specific motion blur look for moving objects. In this video we will focus once again on using the V-Ray physical camera to create such an effect for ourselves. As you can see we have loaded our Ch_ 08_Pool_Table_Start scene file again. What we haven't mentioned up to this point is the fact that there is an animation already setup in this scene. You can see we have a big simulation that just provides some motion that we can use to create a motion blur effect for ourselves.
Now if we just come to frame 15, this is a portion of the scene that we are going to want to render, we do of course need to make certain that we are rendering through our motion blur cameras; we have three of them settled in the scene, as you can see. Let's just switch to our first one, we do of course need to select this camera so we can work with it parameters. Before we make any changes to them of course we just want to show you we've got going on in this portion of the animation. So if we just screw up a little bit either away from frame 15 backwards and forwards you can sere there is just some gentle motion on our cue object that's just weighing up the cue ball and of course it sends it off down the table.
Now as motion blur is of course a render intensive process, we are working with some pre-rendered images, if we just pull our Render View you can see these in here. You can of course view these images if you want to examine them as well, they are found in your assets folder in the Ch08 folder so follow along if you want to with these particular images as we work through changing the parameters then seeing how that affects our final renders. So as you can see at this moment in time with no motion blur effect enabled in our system we get no sense of movement in this particular frame.
So let's go and turn on Motion Blur, let's come all the way down to the bottom off our V-Ray physical cameras attributes. We have our Enable Motion Blur option that we want to check and of course we're going to just increase the quality of final render a little bit by increasing our Subdivs setting to a value of 12. Now we can come and examine the control mechanism for our Motion blur which as with a real world camera is the shutter speed value. In a real camera a lower shutter speed is often employed in low light situations, it allows the camera to gather more light into the system, will make our exposures brighter.
Of course a side effect of that is the fact that any motion inside the camera's field of view is picked up as a motion blur affect. The lower the shutter speed, the most sensitive the system is to any motion, the greater the blurring effect that will occur. And of course it is exactly the same inside of the V-Ray physical camera. So we currently have our Shutter speed setting at a volume 1/40th of a second which is absolutely fine for the slow animation, the gentle animation that we've got in this portion of the scene. Of course we are going to need to compensate with our other Exposure controls, we can work with f-stop or with our ISO values.
I tend to work with ISO simply because it doesn't affect any other effects in the scene. Of course if we change our f number value, it can change any of the depth of field effects that we may have settled in the scene. So I am going to set the ISO value down to 40 and with those changes made we would go from this to this. And as you can see we now have albeit a subtle motion blur effect but we definitely get a sense of motion on that object. Well let's jump forward a little way in terms of our animation, let's jump all the way down to a around about frame the 47.
Now here, as you can see our cue ball has disappeared so we need to switch cameras to capture it, let's go to Cam_02. Of course we need to select that camera's controls, we need to come down in the system and enable Motion Blur. Let's set our Subdivs to a value of 12. Again, we need to examine our controlling mechanism. Here you can see we have got a slightly less sensitive Shutter speed value of 50, that is fine, our ball is traveling cue object was in the previous frame, so that should work just fine.
And our ISO value has been changed accordingly, because well we don't need to be compensating quite as much because our Shutter speed has not come down quite as low. So with those settings you would see we would get this particular capture and as you can see we have a strong Motion Blur effect on our cue ball, because 50 is still a fairly sensitive value in this particular instance. So we capture a nice strong motion blur effect as our cue ball heads towards the pack there. Now let's just move along a few frames in our simulation just because we want to show something very interesting to you.
Let's move along to frame 51, here you can see we have our cue clearly in the frame. But if we were to take a render of this particular frame, this is the effect that we would see. Now this is occurring because of the way that V-Ray performs its motion blur sampling, it samples forwards and backwards along the timeline. Now if we just demonstrate to you what happens in the very next frame, you can see that our cue has actually left the frame complete. Because V-Ray is aware that is going to happen, it is able to capture this ghosting effect.
We just wanted you to be aware of how V-Ray was performing this sampling, because well if you see this affect in any of your animated sequences you may need to check whether or not objects are leaving the frame instantly, that would definitely produce this affect due to V -Ray's forward and backward sampling. Well again, let's move forward just a little bit in time, this time to frame 54. We now want to switch cameras, so let's switch over to our Cam_03. Select the Settings and of course come down and enable Motion Blur in the system, change our subdivisions value.
Now we can examine our controlling mechanism, you can see here we have got our Shutter speed and ISO value set; these are not really going to work in this portion of the animation. Quite a number of the objects in the scene here are moving quite slowly. So we are going to need some sensitive values in here to capture that Motion Blur for ourselves. So what we are going to do is set our Shutter speed to a value of 5 and we are going to set our ISO to a value of 10. Now with those changes made if we go and take a render, you can see we would get this particular motion.
You can see that with these very sensitive settings in our parameters that even this very slow moving object here has some Motion Blur on it,. Of course, because we have some reasonably fast objects, we are getting some very exaggerated motion blur due to the sensitivity of settings we are working with. Now when it comes to rendering to a motion blur affect using the V-Ray physical camera, new V-Ray users may unaware that there are auto parameters that will affect our final result, parameters that are not a part of the V-Ray's physical camera's parameter set.
If we come up to our Render Settings window, if we come into the V-Ray tab, let's close Image sampler and come into our Camera rollout. You can see amongst the other camera effects in here that we have a Motion Blur option. Again, we can work with creating motion blur in standard Maya cameras using these controls if we wanted to. But in here you can see there are a couple of options that are already accessible. So for instance we have our Prepass samples option, this controls how many samples in time will be computed in during a radiance map calculations.
If we are using a radiance mapping and motion blur then this is an option we need to be to be aware of we may need to come and change values in here to get a good end result. We also have our Geometry samples option; this determines the number of geometry segments used to approximate Motion Blur. Objects are assumed to move linearly between geometry samples in the sampling process. If we have fast rotating objects then we may need to increase this value in order to get correct looking Motion Blur for ourselves.
We also have this Camera Motion Blur option. Now if we were creating an animated sequence where we wanted for instance to create a full frame Motion Blur effect, in other words it was the movement of the camera that was creating the blurring in the frame, not just one or two objects in there. Then we need this option to be checked. Now if we just enable this system you can see we get access to this parameter. If we have left that unchecked with the system turned off, even though we have Motion Blur enabled in our V-Ray physical camera we cannot now create full frame Motion Blur.
So just be aware that that option an important, so I am just going to make certain that remains checked even though this particular system is off. So creating motion blur using the V- Ray physical camera is a quick and easy process, once we have the hang off using the standard photographic conventions that are apart of the V- Ray physical cameras make up. Shutter speed is the control mechanism for Motion Blur and quite literally less is more. If we have slower shutter speeds we will always get more motion blur just as a real camera is.
Do remember, if we are using the Exposure Control set on our V-Ray physical camera to deal with lighting levels in the scene, then we are going to have to do little bit balancing so as not to overexpose our scenes whilst we are pursuing our Motion Blur effect. Well let's leave camera effects behind now and move on to lighting and let's have a look at generating some caustics in our scene.
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