OER-3D - Rendering Videos with GigaMesh – Showing a Rotating Object

Author: Hubert Mara

GigaMesh provides the possibility to create simple and short videos that play in an infinite loop by rotating an object about an axis and exporting a stack of images. These images can be used by other tools like ffmpeg to create a video in a format of your choice.

Steps for Rendering

  1. Open the file and set the light, colors, etc.
  2. Configure the desired resolution of the video using “Export Screenshot” => “Video Frame Size (Set)”. Enter two values for width and height in pixels. The default values for 720p are “720 576”. After entering these values, the size of the GigaMesh is changed accordingly, and “Video Frame Size (Fix)” is activated. Current standard resolutions can be found on Wikipedia.
  3. “Export Image Stack” => “360° Circular Orbit Vertical Axis” will be the best choice for most objects. For cuneiform tablets, choose the horizontal axis. There are two more options using an arbitrary axis, either as normal or the so-called mesh plane, or a selected vertex.
  4. You will be asked to select the directory to store the images, which will number in the hundreds.
  5. Dialog Box “Do you want to turn off the grid?”: It is recommended to select “Yes” as the fine lines tend to flicker in videos.
  6. Dialog Box “Do you want to turn off cropping?”: Select “Yes” as this will ensure the images have the same width and height as the video size set before. “No” is for tasks other than creating a video.
  7. Dialog Box “Do you want to save the metadata per image in .TTL?”: This is only useful if you plan to publish the images including their technical metadata. So, “No” is recommended. TTL files are in Terse RDF Triple Language (Turtle).
  8. Dialog Box “Do you want to use tiled rendering?”: Similar to cropping, answering “Yes” will alter the width and height of the images. So, “No” is recommended.
  9. GigaMesh will create images with a sequential number starting with the filename “gigamesh_still_image_00000.png”. By default, 1350 images are rendered.

Further Processing

The video can be created using another tool, such as ffmpeg on Linux. A minmal example is:

ffmpeg -i gigamesh_still_image_%05d.png -s 720x576 -b 6000k your_video_name.mkv

More recommended are parameters to compute a video with wider supported codes like x264 and higher resolutions like 4k (3840x2160):

ffmpeg -i gigamesh_still_image_%05d.png -s 3840x2160 -c:v libx264 -r 30 -pix_fmt yuv420p your_video_name.mkv

Optional Configuration

The above command will generate a video with a length of approximately one minute. You will notice that the rotation of the object accelerates for the first 10 seconds and slows down for the last 10 seconds. This time can be set in GigaMesh with “Export Image Stack” => “360° Slow rotation duration (seconds)”.

Example for rendering a cuneiform tablet

Cuneiform tablets are typically rotated around the horizontal axis and are in portrait format. The latter is similar to today’s smartphones. To maximise detail and show the characters in the correct orientation, a high-resolution video in portrait format is optimal. This can be created following the steps above with the following differences:

The video shown below than was compiled using the still images. Than the logos (logos.png), the QR code (hs1445_big.jpg) and the license line (hs1445_license_final_big.png) were added in three steps:

ffmpeg -i gigamesh_still_image_%05d.png -s 2160x3840x -c:v libx264 -r 30 -pix_fmt yuv420p hs_1445h.mp4
ffmpeg -i hs_1445h.mp4 -i logos.png -filter_complex "overlay=x=1450:y=10" hs_1445h_logo.mp4
ffmpeg -i hs_1445h_logo.mp4 -i hs1445_big.jpg -filter_complex "overlay=x=1650:y=3200" hs_1445h_logoqr.mp4
ffmpeg -i hs_1445h_logoqr.mp4 -i hs1445_license_final_big.png -filter_complex "overlay=x=10:y=3750" hs_1445h_logoqr_license.mp4

The tablet is from HeiCu3Da having the inventory number HS 1445 directly accessible and citable doi:10.11588/heidicon/1115892.


Advanced Example

As simple as this may seem, it allows you to render multiple variations of a rotating object, for example. These can be blended using video editing tools and enriched with other images, as shown in the GigaMesh tutorial video Advanced documentation methods in studying Corinthian black-figure vase painting on YouTube with the rotation starting after the intro (19 seconds).

This video is also available as publication doi:10.11588/heidok.00025189