How to correct the horizon of a timelapse made with Tikee?

Thanks to the wide field of view (220°), the images captured by Tikee are presented in a panoramic format. Due to this, you may occasionally observe 'distortions' when the camera is tilted during installation: lines that are actually straight might appear curved in the photo.

In this professional-level technical blog post, aimed at advancing beyond our earlier discussions, we delve into correcting the horizon line to produce a timelapse with Tikee that is more visually appealing.

From a technical standpoint, our images are projected as an equirectangular format (more info at wikipedia), and while we do not capture a complete sphere like you would in a VR video, we trim the edges to display only the portion with visible content.

It's possible that a camera was not installed flawlessly horizontally, or that it shifted during filming, or that the environmental conditions where the shot was taken did not permit a horizontal camera setup.

For these reasons, you might have noticed an unwanted sharp curvature in the skyline that could appear unsightly.

In this technical blog post, we aim to guide you through correcting the horizon line to achieve a timelapse with Tikee that is more aesthetically pleasing.

Why Panoramic Images Can Be Distorted

Technically, our images are cast in an equirectangular format. Considering we don't encompass a full sphere, we crop the edges to showcase only the content. At times, the camera may be positioned imperfectly horizontally, it might have been nudged during shooting, or the shooting setting might not cater to a perfectly horizontal arrangement. These scenarios can lead to a bending horizon line, which can be unattractive.

Necessary Equipment

For this tutorial, you will need:

• Your panoramic photographs sequentially named with an index.

• Adobe Premiere Pro editing software and its VR plugins. In this more sophisticated post compared to our previous ones, we will look at how to rectify the skyline and create a more aesthetic timelapse.

Creating the Project

For our example, the camera set up for the Vivatech 2019 event was angled downwards to fully capture the exhibits. However, an unpleasant curve is noticeable on the skyline (the windows). Through this guide, we will straighten this line and crop to emphasize the assembly of the exhibitor's booths.

Our initial working environment

Sequence Composition The central concept that we will utilize later is "sequence composition." In the sense used by Adobe Premiere, a sequence has specific attributes like image size, frame rate, preview settings, among others, and encompasses an array of video clips. Nevertheless, a film could also be considered a single video clip that can be incorporated into another film. The latter may possess distinct parameters. Hence, we will:
Integrate our 'original' sequence into a larger sequence that represents a complete equirectangular video (VR 360),
Apply a rotation effect to the VR sphere for this new sequence,
Crop the final sequence,
Export the media.

Integration into a holistic equirectangular format

The equirectangular layout is traditionally used in 360-degree imagery to depict an entire sphere: a horizontal span of 360 degrees and a vertical range of 180 degrees. Although Tikee does not capture this entire field of view but only a piece of it:

To employ 'VR' effects, creating a sequence that encompasses the Tikee view is necessary: 6960×3480 (adjust according to the sequence's initial resolution using the formula: HEIGHT = ORIGINAL_HEIGHT / 0.441 and WIDTH = 2 * HEIGHT), for a source image of 4260×1534.
Let's initiate by generating this sequence: Right-click in the bin > New item > Sequence.

Setting up a sequence

In the sequence's settings, insert the demanded dimensions: 6960×3840 in our scenario:

Sequence parameters

Rename the sequence to 'FullFrame' for clarity and distinction later on in the process.
We also suggest saving the preset that resulted by clicking on 'Save Preset.' We will use this preset later in the tutorial, referred to as 'Tikee_4260x1534':

Preconfigured sequence settings

Your collection now includes a newly formed empty sequence titled 'FullFrame.' Introduce the 'original' sequence by dragging it onto the timeline:

You will then encounter an alert stating that the sequence sizes do not match. That is precisely our intention, so maintain the current settings.

Your 'FullFrame' sequence now epitomizes a complete equirectangular video and encompasses the Tikee snapshots.

Horizon Correction

Implementing the VR Sphere Rotation Effect

We will now apply an effect from the 'Immersive Video' group to this clip. Subsequently, we will incorporate it into a sequence of the identical dimension, dubbed 'FullFrame_horizon.'

Reproduce the initial step 'Creating a sequence' and select the 'Tikee_4260x1534' presets. Title this sequence FullFrame_horizon.

Next, add the 'FullFrame' sequence by pulling it into the timeline. We can now apply the 'Rotation Sphere VR' effect to the 'FullFrame' clip within the 'FullFrame_horizon' sequence.
To do this, pinpoint the effect in the 'Effects' panel (frame 1 in the succeeding image) and drag it to the 'FullFrame' clip on the timeline.The effect will then emerge on the sequence's video effect list (frame 2).

Add an effect to a clip

Adjusting the Settings

You may then finesse the 'Tilt,' 'Pan,' and 'Ripple' settings of the VR sphere effect to recalibrate your horizon.

Horizon calibrated

You can observe in the prior image a marker intended to aid in precision adjustment of the horizon. To insert a marker, click in the preview segment of the video, then View > Add Marker.

Inserting a marker

Upon achieving satisfaction with the settings, you may advance to the subsequent phase. Note: This effect can also be used with the timeline to stabilize your timelapse captured with Tikee. Simply intersperse keyframes with varying orientations. We may revisit this in a future blog post.

Creating a Cropped Sequence

To generate a video void of black borders, you merely need to establish a new 'Reframed' sequence with the precise dimensions and include the 'FullFrame_horizon' sequence within it.For our case, we aim to preserve a panoramic format identical to Tikee's original timelapse, thus we create a 4620×1534 sized sequence titled 'Reframed'.

Herein lies the result:

Adjusting Position and Scale

We can observe persistent black areas. Adjusting the clip's position and scale in the sequence is required.This is accomplished by modifying the 'Position' and 'Scale' parameters of the 'Effect Controls' effect, which is by default activated on all clock in the sequence:

Exporting the Final Sequence

Following the 'Effect Controls' modification Note: the effect is dubbed 'Effect Controls' for, when deployed with temporally varying parameters, it facilitates a 'pan and zoom' action within the video. In a subsequent blog post, we'll discover that it is feasible to execute even more advanced motions in a timelapse recorded with Tikee.Now, your culminating sequence is primed for rendering.

The finalized video: here.

We trust this article has been beneficial! Stay tuned for another technical piece on creating timelapses with Tikee.