The Gardeners House at Mount Vernon
Hybrid Drawings are a mixture between measured line drawings, rectified photography, and 3-D point clouds.
In broad terms, a hybrid drawing is any drawing that mixes and superimposes a variety of ideas, techniques or media into a new, meaningful image – something that architects & designers have long gravitated towards. The hybrid drawings that I create for historic preservation projects are special sub set of this general category because they are measured drawings.
Fidelity to the real size and shape of existing surfaces.
Hybrid Drawings make dimensional accuracy the conjunction point between various digital media. When a line drawing – either as a projected elevation (in 2-D) or as a “wire frame” model (in 3-D) – accurately represents the real world size and shape of a surface, it can be superimposed over another description of the same surface in a different media. In my work these additional media include both rectified photographs (aka ortho-photos) and 3-D point clouds derived through photogrammetry and/or laser scanning.
Merging CAD delineation with rectified photography produces a hybrid drawing. These different types of description can occupy the same “space” because they each depict the same object or condition – albeit in different ways. The line-work establishes precise edges between vertices while the pixels describe material color and condition. In short, measured hybrid drawings integrate the quantitative description of vectors with the qualitative description of pixels.
When considering a hybrid drawing, one wonders: is it a photograph that behaves like a drawing (since it is scale-able) or is it a drawing that looks like a high quality photograph? The answer is yes!
The Virginia State Capitol
How are hybrid drawings delivered/shared?
Typically I deliver measured hybrid drawings in AutoCAD format in which the line-work is composed of AutoCAD vector entities and the raster imagery consists of JPG images that are referenced into the drawing. Often, the raster images are many (created from different vantage points) thereby creating a mosaic image of the subject.
HABS Standards have long dictated that good professional practice in documenting existing structures should include both measured drawings and photographs. Hybrid drawing techniques allow these two types of documentation to work together in a new and powerful way.
