(12-19-2023, 06:32 AM)Michigan Swamp Buck Wrote: For as long as I have gone to college and studied and worked with digital graphics in the past 30 plus years I have never heard about what you describe here. I even worked with stereo images I produced and developed in my own darkroom as well as built my own stereoscope to view them with. When I got into digital images I made a pair of red-blue filter glasses to view my 3-D images with, that trick helped me land a good graphics job too.
But what you have described makes absolutely perfect sense when I think about the grayscale images I've made and worked with over the years. What a great concept, it should have been covered in my fine arts college classes (too long ago I guess) I bet it was used on NASA projects all the time. Kudos for that information.
While the grayscale heightfields technically ARE raster graphics, using them as a graphic image is not the purpose of them, so that's probably why they were not included in graphics art courses. They're more of a "Geographic Information Systems" (GIS) thing, for use in mapping and terrain analysis.
I learned to work with them years ago when most of the geographic analysis data I was getting was in the form of Digital Elevation Models (DEMs). A DEM is just a great big file of nothing but numbers, were each number is the elevation of a particular point on a grid. Software figures out how many rows and columns are represented, and then arranges the elevation values at the proper intersections of the grid.
Grayscale heightfields, on the other hand, do give a sort of a visual representation of the same data, being raster graphics, but their true beauty is only displayed when they are used to create terrain images of landscapes that can be lighted from whatever direction you prefer to bring out the details you are looking for. They effectively create 3D images of Earth's surface that can be rotated and manipulated.
They're used for things like slope analysis and to figure out what areas of land are masked from which locations - useful for setting up ambushes or antennae for line-of-sight radio communications, or setting things like artillery emplacements..
Programs I used them with included "3DEM", which has been defunct for years as the author stopped updating it - pity, it was a pretty nifty program - "MicroDEM" written by Peter Guth at the USNA, where it was still hosted last time I checked, the associated Army version called "Terrabase II" (was hosted at Ft. Leonard Wood by the Corps of Engineers), and a program called "Terragen" which is used to create photorealistic landscapes and can use either real terrains or just made-up fractally generated terrains. The program doesn't know if it's real or not, it just knows it's a grayscale image that needs to be made into a landscape..
It's hard to get DEMs any more. it seems like the USGS has stopped supporting them. All of the data I've gotten from USGS in the past couple of years has been in the form of grayscale heightfields. Data quality for those has increased dramatically. DEMs could be got in 1 KM, 90m, and 30m grid spacings - one elevation measurement for each point on the grid - and some few select ones in 10m grid spacings. The last few grayscales I've got were down to 1m grid spacings, 10X the resolution of the 10m DEMs, 30X the normal 30m DEM grids. Much bigger files, but much better resolution. I can pick out creek terraces and ATV trails on some of the local ones I've got.
I'm fixing to go to bed now, but maybe when I get up I'll try to pick out a couple examples to demonstrate how they work. Once one sees that, it should be readily apparent how it works with the image on the Shroud of Turin.
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