In the PDF graphics context, “lines” have fundamental properties that have no equivalent in SketchUp edges. This caused problems with loops not closing when I attempted to convert filled paths to SketchUp Faces. Because they have width and end handling, two lines can appear to meet at a vertex when in fact they leave a gap or are misaligned. In many samples I tested, I also found that the painter’s algorithm causes people to be imprecise when drawing lines in PDFs. The equivalent in SketchUp would be that every path created would need to go into a new group! But even then, if the Faces (filled paths in PDF) were drawn on the same plane, you would get massive z-fighting in SketchUp because OpenGL does not use the painter’s algorithm. Said another way, the only memory the graphics engine has of what was drawn previously is the digital “paint” on the “canvas”, not what operations it came from or what it “is”. Each successive item drawn simply overlays whatever was there before, without merging, blending, intersecting, or otherwise interacting with it. That is, the conceptual model is of layers of paint applied to a canvas. The difficulties start with a fundamental aspect of how the graphics engine operates: it uses a “painter’s algorithm”. The graphics engine takes care of issues such as anti-aliasing based on the physical properties of the output medium and the overall scale it is told to use. Many PDFs create a new graphic context for each path. There are also other uses of paths, such as creating clipping boundaries. After creating a path, the program tells the engine what to do with it: either “stroke” (output it as a line) or “fill” (output it as a filled area). For a vector PDF, It then contains instructions on how to create a “path”, which is a sequence of commands saying things such as “move to”, “draw line to”, “draw arc to” with their associated parameters. The program creates a “graphic context” that contains basic info such as coordinate system (origin, scale, transformation), fill patterns, line joint handling, etc. Unless you are a developer or propellor-beanie type, you can stop reading at this point Maybe someone more clever than I can see ways to deal with the issues…Ī PDF actually contains a program that is executed by a drawing engine to generate the graphic output. I ran into what seemed insurmountable differences between their modeling concepts, and I gave up.īelow is a discussion of what I found. I once attempted to create an importer to bring vector PDF into SketchUp as geometry, not as an image as currently done by the Mac importer.
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