VFX1 DD1410: Car Pan Shot Rotoing, Rotopaint and Tracking

The second part of Brief 03 requires a little but more work than the car colour correct. The link for the blog post regarding the car colour correct is below:

http://www.darthspockvfx.blogspot.co.uk/2012/11/vfx1-dd1410-rotoing-and-colour.html

The different between this piece and that piece is that in this there is moving footage. This means that tracker nodes will need to be used in order to keep the car in place. The footage pans from the sky down to the beginning of the pavement. This means that the car isn't in the view for a lot of the footage.

The footage for this piece can be seen using the link below:

http://www.darthspockvfx.blogspot.co.uk/2012/10/vfx1-dd1410-brief-03-car-colour-correct.html

To begin with, open Nuke and read in the pan footage of the background.

Next the car needs to be read in. Since the car doesn't move or change in anyway in the duration of its footage, one can save themselves a lot of work by simply reading in a single still rather than the whole footage. For example, in this picture the still shot 170 has been used.

The next step is rotoing the car. The same rotos cannot be used from the car colour correction piece because they will not work properly with the trackers.

Unlike the last piece, this time the shadow and wheels have been roto'd along with the body of the car. Also this time the boot lid of the car is closed, which means there is less to roto.

Next we need to merge the car and the new background together. So a merge node needs to be read in.

The A goes into the roto which is still attached to the car footage, and the the B goes into the new background.

Now the background footage needs to have the trackers put in place. This requires at least two stand out points in the footage. One of which is a white stone which can be seen in the picture below:

Attach a tracker node to the background and track this stone.

Make sure the track is clean and straight. Next a transform node needs to be read in and attached to the roto node for the car. The tracking information from the tracker needs to be copied across to the transform node.

The information from the tracker can be found in the transform section of the tracker node.

The information that is needed is the center. Copy this across to the translate section of the transform node.

This should place the car roto on the tracker. A way to tell if the transform and the tracker have linked properly is represented by the green line between the two.

If the car hasn't moved onto the track properly, then it will have to be moved manually. This can be done by right clicking on the translate section of the tranform and selecting edit expression. From here points can be changed and the car moved to the right place.

The next step is the second tracker, this one will keep the car ground whilst the footage plays with the sky frames. A second tracker and transform needs to be read in and attached on the node tree as shown below:

In the picture above the tracking information has already been carried across to the second transform (as represented by the green line.

For this one, one of the green poles has been used as the tracking point, the tracker point was placed on on the first frame where the top of the fence pole comes into view.

After making sure that a clean track has been accomplished, the trackers must be checked to make sure that they do not overlap. The trackers route can be seen on the timeline. It is represented by blue points.

An easy way to make sure that the trackers do not overlap is to find on the timeline where one starts and the over should begin and do a clear forward on one and a clear backward on the over. This means that they should follow on from each other without incident.

Now it is time for the colour correcting. This is the easy part. Copy the colour correct nodes from the car colour correct piece and place them on the node tree.

The colour corrects may been altering slightly. In this piece the car and background looks a lot less saturated than in the car colour correct piece. The piece can be altered in any way, for example, this one could be made to look like it is at a different time in the day to the car colour correct piece.

Now the tricky bit, the windows. In the car colour correct this was an irritating bit to work out. A way has been found that makes it really simple. This involves using the rotopaint node rather than a roto node. Read in the rotopaint node and place it on the tree.

Using the reveal tool (shown below), draw around the windows like in a roto. The main difference is that the winodw must be completely filled in. The easiest may to do is is to is to view the rotopaint and click the A key whilst hovering the mouse over the image to view the alpha channel. This way one can see what is being revealed more easily. It is best to draw around around the edge of the windows before viewing the alpha channel.

The black areas of the windows in the picture above show what has been revealed. When using the reveal tool it is important to get the areas as black as possibly, to reduce spill and get a clearer image. A picture of the icon for the reveal tool is below (the mouse icon for the reveal tool is the same as the picture below):

If a mistake is made, then there are over tools, like an eraser, that can be used to fix the mistake.

Within these icons there are also other tools that can be useful. Like a blur tool, with will work in the same way as the reveal tool. A blur would be useful with this piece to try and give the windows the appearance that they are being viewed through the first set of windows.

The reveal basically allows some to select what they want to get rid of in a shot. Using this node on the car, one can take out the image of the grassy plain and reveal the fence from the new background behind it (since the car was placed on top of the background, the original background is still behind it). By placing the rotopaint onto the node tree on the same branch as the roto, it means that the tracking information that was applied earlier, applies to the rotopaint as well. So the windows will follow the car perfectly. 

The picture above shows that the windows now reveal the right background. Sadly the colour correct will not effect the windows for some reason, so the best thing to do is to go to the rotopaint node in the properties bin and change the output and the premultiplier to alpha (for some reason this gives the windows a more glossier appearance).

Then use the blur tool withing the rotopaint and add a slight blur to the windows. This will give the windows a more realistic look.

A picture of the node tree so far is below:

Below is a video of the car pan so far is below:

Upon reviewing the footage, it is clear that another tracker is made. The footage shows that as the camera moves down, the car is supposed to go out of shot. Instead of this happening, the bottom of the car lingers and gets dragged down with the camera. A third tracker can be used to keep the car in place.

That is the end of this blog post, in the next one it will reveal how to use the third tracker to sort this recent problem.

VFX1 - DD1410: Altar Sequence Rotoing First And Final Shot

The altar sequence has many different elements to it, some of these include rotoing, tracking and keylight.

 The brief for this piece is in the link below:
http://www.darthspockvfx.blogspot.co.uk/2012/10/vfx1-dd1410-brief-01-altar-sequence-001.html

To begin with, lets take a look at the opening sequence:

The video below shows the first shot, frames 0-61 (and a little bit beyond that into the second shot, which is the blue screen bit).

According to the brief, in this first shot the altar and the dragon statue need to be roto'd in case they are to have some sort of effect added to them later along in post-production.

Unlike the car colour correct, this piece has a lot more shots in it, so to make it easier for anything doing work on the footage, it is best to split up each shot. This can be done by creating a backdrop and placing everything from a certain shot in it.

When it comes to rotoing the altar and the dragon, it is best to split the altar up into sections, just in case the director wanted to have a certain effect on a particular part.

The footage also needs to be stabilised. To do this a tracker must be read in. Track from frames 0-61, make sure the tracker is set to stabilise.

Attach the trackers to stand out points on the dragon and altar. In this picture the points that have been chosen are two of the corner points and the ball on the top.

If the tracker jumps at any point or fails to track properly, one can either track it again, or go in and move the track route by hand.

Now that the footage has been stabilised, the tracker should stay with the dragon and altar, at most some tiny adjustments may be needed.

Since the footage has been stabilised, a transform node needs to be read in to zoom in the image. This is because when the footage was stabilised the tracker zoomed in, cutting out the edges, but leaving the viewer the same size. This is represented by a dotted line around the edge.

That is all that needs to be done with the first shot, the last shot (frames 355-449) is very similar.

With this shot, the dragon and altar need to be roto'd again. Unlike the first shot, this one cannot be stabilised because when the girl walks away the shot moves quite a bit, and stabilising cuts out too much of the image (as seen with the dotted line around the viewer in the first shot).

Whilst the camera is following the girl, the altar and dragon move too, so the roto needs to stay with them whilst the footage plays on. To do this a tracker node needs to be read in.

First, like in the first shot, attach the trackers to points on the dragon and altar that stand out.

Then copy across the information from the tracker to the roto. This includes the translate, the rotate, the scale, the scew and the center. 

Now the roto should follow the tracker and keep it with the dragon and the altar.

If the roto doesn't completely follow the track, then one can go through the frames and alter the roto where needed.

The next blog post will include a break down of the use of the keylight node in this piece.

VFX1 DD1410: Rotoing And Colour Correcting The Shadow and Windows

This post continues on from where the last one ended. If you did not see the last post, check the link below:
http://www.darthspockvfx.blogspot.co.uk/2012/11/vfx1-dd1410-rotoing-car-merging-footage.html

To begin, the shadow needs to be roto'd. It is easier to roto the wheels along with the shadow because it guarantees that there will be no gaps between the wheels and the shadow.

 Next the roto needs to be brought into the current merged footage. To do this another merge node needs to be read in, this node is then linked to the shadow roto and the last merge (the one merging the two colour correct nodes together).

Now that the shadow has been merged, the roto needs to be positioned in its proper position beneath the car. To do this, a transform node is read in.

In its current state, the shadow stands out too much, it doesn't match the car or the background, so the shadow also needs to be colour corrected.

Once everything has been colour corrected, if at a later stage the footage needs to be altered in some way, other nodes can be attached to the second merge node.

For example, a grade node:

In this example, the saturation has been increased:

An obvious part of the car that needs dealing with is the windows, when the car roto is merged it perfectly carries across what was roto'd. This means that the original background (a grassy field) is still visible through the windows.

So the next step is rotoing the windows. This can be done on the original background.

This roto is then attached to the new background. To do this a new read node needs to be read in. 

This ensures that when the roto is merged into the new footage, it will show the gate through the windows rather than the grassy field.

The next step requires a bit of preparation. The windows need to be merged into the new footage, but before that is done, read in the nodes that would be used to colour correct and altar the windows roto, but don't do anything with them yet.

These include a transform, a blur, a colour correct and an edge blur.

Now the windows roto can be merged. Read in a new merge node, linking it from the edge blur, to the second merge.

Now the windows are a part of the new background. Using the transform node, they can be positioned on top of the current windows.

Then using the colour correct node, the windows can be altered to match the colour of the rest of the background, and using a mixture of the blur and the edge blur, it will give the impression that one is viewing the windows through another piece of glass (the front windows).

As a little bit of extra alteration, another blur node can be read in to try and give the car a more definitive focus.

This is the node tree in full for this car alteration piece:

It is important to keep note of what has been done in this piece, because when it comes to doing the car alteration pan shot, the colour correct nodes can be easily copied across. Meaning that a person can spend more time concentrating on the like of tracking (which will definitely be present in moving footage) and not worry about replicating the same results as in this piece.

The blog post about the pan footage is below:
http://www.darthspockvfx.blogspot.co.uk/2012/10/vfx1-dd1410-brief-03-car-colour-correct.html