Diego Rivera, The Marriage of the Artistic Expression of the North and of the South on This Continent, also known as Pan American Unity, 1940, 6.7 meters tall by 22.47 meters wide (22 X 74 feet); courtesy City College of San Francisco; © 2020 Banco de México Diego Rivera and Frida Kahlo Museums Trust, Mexico City / Artists Rights Society (ARS), New York; Color and Shape Images - © Cultural Heritage Imaging.
“For years I have felt that the real art of the Americas must come as a result of the fusion of the machinism and new creative power of the north with the tradition rooted in the soil of the south, the Toltecs, Tarascans, Mayas, Incas, etc., and would like to choose that as the subject of my mural.”
Pan American Unity is a big mural. Documenting it required a big 3D model. The 3D documentation, made up of 8.1-billion shape and color measurements, contains a wealth of information about the surface shape and color of the mural. Cultural Heritage Imaging (CHI) has used the 3D data to make two special types of high-resolution 2D images; orthomosaics depicting the mural color and Digital Elevation Models (DEMs) showing the fresco’s surface shape.
The video below explains how to explore the shape and color layers of the mural imaging (see the video transcript):
The Color Layer
The color layer shows the colors of Pan American Unity just where Diego Rivera painted them. This color layer, called an orthomosaic, is made with information derived from the 8.1 billion colored points in the mural’s 3D model.
The Shape Layer
The shape layer uses changing color to show the working imprint of Rivera’s brushwork in the fresco’s wet plaster surface. As the depth of the textured plaster changes, the color of the surface changes. The shape layer, called a Digital Elevation Model (DEM), is made from the shape information acquired in the mural’s 3D model.
These 2D outputs are a result of 3D capture of the mural surface using photogrammetry. CHI used 2469 50-megapixel images to create the 8.1 billion point 3D model.
** The full resolution of the orthomosaic (color) and Digital Elevation Model (DEM) (shape) is 163,864 pixels across by 49,177 pixels tall totaling 8.06 billion pixels or 8.06 gigapixels. While Stanford Libraries has preserved these very large images, a requirement to prevent full download of the artwork means that we can only display reduced-size versions of the images at this time. We have made a temporary compromise between offering the rich detail captured by the full resolution images and what can be feasibly delivered in the user interface. We hope to be able to make the full resolution images of the entire mural viewable here in the future. In the meantime, full resolution images of lower panel 5 color and shape are available on the 2D Color and Shape from 3D Data page.