Looping Background

Revision as of 11:54, 20 March 2012

Language:

English

Introduction

A looping background is a moving background that simulates camera panning, and that seamlessly repeats itself. It is a standard animation technique.

There are multiple ways to do looping backgrounds in Synfig. The one presented here is simple, minimizes manual work and repetition, and doesn't use keyframes.

We will be using two files: one for the background and one for the animation.

Say that the animation size will be WA = 640 pixels, HA = 480 pixels.

The background image

The background can be a bitmap or a vector graphics. In order to be usable as a looping background, the requirements are the same. Imagine duplicating the image and putting the duplicate next to the original in an horizontal line: the left edge must seamlessly blend with the right edge.

This tutorial uses a vector graphics background, but the same workflow can be applied for bitmap images.

If you already have a background, skip to the next section.

Create background

Since we are creating the background and the animation from scratch, the easiest way is to use the same scale for the two synfig files.

In Synfig Studio, create a new canvas with File | New. Its height should be the same as the animation (HB = HA = 480), while its width should be bigger than the animation (no need to be a multiple). Say WB = 1200. To be sure to keep the correct background size when importing it into the animation, proceed as follows:

Open the Canvas Properties Dialog (Caret | Edit | Properties). In the Other tab, check pixel width, pixel heigth, image aspect, pixel aspect. Uncheck the other items. In the Image tab, finally put the size: Width = WB = 1200, Height = HB = 480. All the other values should be automatically updated.

Now draw the background :-). This is the one we will be using for the tutorial:

Workflow overview

1. Prepare or gather background.
   1. Mention trick to keep same size when importing a sif file.
   2. Mention trick to keep the two ends the same (exported, decomposed vector).
2. Import background.
3. Genete's trick of the Zoom layer.
4. Duplicate encapsulated background. Say bounding box width is L pixels.
5. Move center of the duplicate L pixels towards the direction of the loop.
6. Add translation layer.
   1. Record mode. Move translation layer opposite direction of loop, L pixels. Two waypoints, one at time 0, one at time T. Exit from record mode.
7. Add Timed Loop layer. Set duration to T.
8. Enjoy!

Examples

Credits

Based on posts by Genete and others in the Synfig forum.

Language:

English