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Camera Solve Module

Overview

The Camera Solve module is used to take planar tracking information and convert it to 3d space.

This is particularly useful if you cannot get a good track on the plane you need, as you can track other planes in the shot and use them to give you track in 3D space instead

As we are dealing with 3D calculations rather than 2D planar projections, the workflow is slightly different to a usual planar track.

Identifying the type of camera movement

In order to get a good camera solve you must first identify what type of track it is. Mocha recognises three types of camera situations:

 

Pan, Tilt, Zoom (PTZ)

Pan, tilt. zoom cameras are generally fixed in place and do exactly what their name suggests; pan, tilt and zoom.

PTZ cameras are looking for overall movement in the camera plane, rather than changes in the physical planes within your scene.

Small Parallax

Small Parallax is where the camera is not fixed to one point in space and has a lot of mid-ground planes that can be tracked.

Large Parallax

Large Parallax is where the camera is not fixed to one point in space and has trackable planes very close to the camera. It is referred to as Large Parallax because closer objects move at much greater perspective and distance to the camera than objects further away.

The Camera Solve Process

Once you have identified the type of camera motion you can start tracking your shot.

Tracking for PTZ-type Camera Solves

PTZ solves are a little different from perspective solves in that they only need to look for how the camera is behaving when fixed, such as on a tripod.

To set up a PTZ solve, take the following steps:

  1. Locate a large area in the shot that can be tracked. If you can't find a single large area, you can also use a variety of smaller ones using "Add Spline To Layer".

  2. Turn on the grid so you can see how the plane is moving.

  3. Set any parameters you need for the track and begin tracking.

  4. If your track pans around more than around 60 degrees, stop the track and create another shape to continue tracking. The second shape will need to start further back in time than where the first one stopped tracking, so their tracking information overlaps on the timeline. This will help the solver blend together the tracking information of multiple shapes.

  5. Once you have tracked the shot, switch to the Camera Solve tab.

  6. Select all tracked layers you wish to use for the solve

  7. Choose either Auto to let mocha guess the right solve, or choose Pan, Tilt, Zoom from the drop-down.

  8. If you select Pan, Tilt, Zoom, set the focal length. Most commonly this will be 35-70mm. You can choose more than one if the focal length changes. Also choose Zooming if the is any camera zoom in the shot.

  9. Once you have chosen your settings, click Solve.

Once mocha finishes solving the shot, you can then export the solved scene. See "Exporting Camera Solves" below for further details.

Tracking for Small Parallax Camera Solves

Small Parallax shots require at least 2 non-coplanar tracks to solve the scene. Non-coplanar means not on the same plane as each other. Examples of non-coplanar areas include:

  • A floor and a wall

  • The side and back of a truck

  • Two camera-facing areas at noticeably different distances from the camera, such as one building in front of another

  • Two mountain slopes at different angles

  • Two opposing walls of a corridor

To set up a Small Parallax solve, take the following steps:

  1. Locate planar areas in the mid-ground of the shot that can be tracked. These objects should not be moving in the shot, so choose areas like walls, ground, tree trunks etc. Planes too close or too far away from the camera may not help a Small Parallax solve.

  2. Turn on the grid so you can see how the planes are moving. Adjust the surface to fit the planar perspective if you need to see this movement more accurately

  3. Set any parameters you need for the track and begin tracking.

  4. If you lose the track due to obstructions or the object moving off screen, stop the track and create another shape to continue tracking. The second shape will need to start further back in time than where the first one stopped tracking, so their tracking information overlaps on the timeline. This will help the solver blend together the tracking information of multiple shapes.

  5. Once you have tracked the shot, switch to the Camera Solve tab.

  6. Select all tracked layers you wish to use for the solve

  7. Choose either Auto to let mocha guess the right solve, or choose Small Parallax from the drop-down.

  8. If you select Small Parallax, set the focal length. Most commonly this will be 35-70mm. You can choose more than one if the focal length changes. Also choose Zooming if the is any camera zoom in the shot.

  9. Once you have chosen your settings, click Solve.

Once mocha finishes solving the shot, you can then export the solved scene. See "Exporting Camera Solves" below for further details.

Tracking for Large Parallax Camera Solves

Like Small Parallax, Large Parallax shots also require at least 2 non-coplanar tracks to solve the scene. (See examples of non-coplanar areas above)

To set up a Large Parallax solve, take the following steps:

  1. Locate planar areas in the the shot that can be tracked. These objects should not be moving in the shot, so choose areas like walls, ground, tree trunks etc.

  2. Turn on the grid so you can see how the planes are moving. Adjust the surface to fit the planar perspective if you need to see this movement more accurately

  3. Set any parameters you need for the track and begin tracking.

  4. If you lose the track due to obstructions or the object moving off screen, stop the track and create another shape to continue tracking. The second shape will need to start further back in time than where the first one stopped tracking, so their tracking information overlaps on the timeline. This will help the solver blend together the tracking information of multiple shapes.

  5. Once you have tracked the shot, switch to the Camera Solve tab.

  6. Select all tracked layers you wish to use for the solve

  7. Choose either Auto to let mocha guess the right solve, or choose Large Parallax from the drop-down.

  8. If you select Large Parallax, set the focal length. Most commonly this will be 35-70mm. You can choose more than one if the focal length changes. Also choose Zooming if the is any camera zoom in the shot.

  9. Once you have chosen your settings, click Solve.

Once mocha finishes solving the shot, you can then export the solved scene. See "Exporting Camera Solves" below for further details.

Solve Quality Indicator

When a solve is complete, the Solve Quality bar will tell you how accurate the solve has been. If you get a poor percentage check to make sure your tracks are locked on accurately, add additional layers to help the solver or try a different solve type or focal distance.

Exporting Camera Solves

You have two steps for camera solves:

1. Export Camera Data from Static Objects

This is the standard export. The basic procedure is:

  1. Select the layers you used to do the initial solve in the layer panel (these are still selected if you have just completed a camera solve). These layers are normally tracked to static objects, such as walls, ground, a parked vehicle, a dinosaur fossil etc.

  2. Do not choose any layers that are tracking moving objects (people, moving cars, badgers etc.)

  3. Click Export Camera Data...

  4. Choose the format you wish to use from the drop-down.

    • If you are exporting to After Effects, click Copy to Clipboard.

    • If you choose FBX, click Save and create a filename.

    • If you choose HitFilm Composite Shot, click Save and create a filename.

  5. You can then paste into After Effects using the "Paste mocha camera" option in the Edit menu, or import your FBX or HitFilm data into the program of your choice.

When you paste into After Effects you will get a camera and a number of nulls depending on the type of solve you did. PTZ will only export a single null to help define the camera motion. The other 2 solves will create a null for each corner of your layer surface objects in mocha.

2. Export Camera Data from Moving Objects

This is a secondary export. The basic procedure is:

  1. Once you have exported a camera from the static solve, select any layers that you used to track moving objects in the shot. If you have not tracked any moving objects you can do this now.

  2. Click Export Camera Data...

  3. Choose the format you wish to use from the drop-down.

    • If you are exporting to After Effects, click Copy to Clipboard.

    • If you choose FBX, click Save and create a filename.

    • If you choose HitFilm Composite Shot, click Save and create a filename.

  4. You can then paste into After Effects using the "Paste mocha camera" option in the Edit menu, or import your FBX or HitFilm data into the program of your choice.

When you paste into After Effects you will get a camera and a number of nulls depending on the type of solve you did. PTZ will only export a single null to help define the camera motion. The other 2 solves will create a null for each corner of your layer surface objects in mocha.

NOTE: You will get a second camera object when you export moving layers. You can delete this camera if you have already exported the camera from step 1 of the export.

Tips for Camera Solves

The resulting track drifts or jumps

This can be from the solver not having enough reliable information from the tracks

  • Check the Solve Quality bar to make sure the solve has been accurate

  • Make sure your planar tracks are accurate and locked on well to their static objects.

  • Check that there is enough overlapping frames in the layers if you have had to do more than one track along the timeline. If you start one track exactly where the last finished, the solver may not be able to accurately blend the resulting data.

  • You may not have enough layers tracked to get an accurate solve. Try adding further tracks to help the solve.

  • Try a different solve type. Sometimes one solver may give better results than another.

  • Try a different focal length.

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