About these pages
The 3D stuff on these pages combines some of my interests: Computing (in particular 3D graphics), astronomy and computerized art. Many of the renderings were created with PT3RT, a renderer/raytracer I'm developing. Other renderings are created with POV-Ray or by combining separate renderings from POV and my renderer into a single rendering. My raytracer is highly specialized for renderings planets, satellites and rings, e.g. the illumination model is optimized for planetary renderings by utilizing theoretical photometric functions from the planetary sciences literature. In fact the renderer is so specialized that the only types of objects it currently can render are spheres, ellipsoids, planetary rings, surfaces, triangles meshes and background starfields. As a "compensation" it produces highly realistic renderings of these objects. My goal now is for the renderings to look as similar as possible to spacecraft photos.
To achieve this the planets/satellites can be rendered using various shading functions, including Lambert and modified forms of it and theoretical photometric functions (e.g. the Hapke and Buratti functions) from planetary sciences literature. The photometric parameters for the red, green and blue color channels can be specified separately (although I doubt it is very useful). Special thanks to Constantine Thomas for valuable information on this stuff and various other things related to planetary science and 3D planetary rendering.
In the future I plan to add several features to the renderer. Ideas include multiple illumination models per planet (e.g. the Earth - the ocean versus landmass), more comlicated atmospheric effects and more types of objects/primitives.
An increasing number of the renderings at this site are done with POV-Ray. Combining objects (e.g. spacecraft) rendered in POV with renderings of planets/satellites from my renderer gives particularly interesting (and realistic) results. The rendering on the main page is an example of this, Saturn and its rings were rendered in my renderer but the texts and cratered landscape in POV using Leveller to create the heightfield. The use of POV is indicated in all cases. In contrast, renderings with no information on how they were done are rendered in my own renderer.
The 3D models and planetary maps
The models used for the renderings are generally either publicly available on the Internet or were created by me. The number one place for planetary maps like those used for the renderings is David Seal's site which has a big and wonderful collection of planetary maps. Constantine Thomas also has a few maps, as well as James Hastings-Trew (they have maps which either David does not have or maps which improve on some of his maps). These maps are publicly available. Some maps are also available at this USGS site. There are also some interesting maps at Calvin Hamilton's Views of the Solar System site but most/all of these are copyrighted. For renderings of the Earth I used the Face of the EarthTM texture map from ARC Science Simulations with permission from them. The Earth bump map I use was created by Doug Fortune from publicly available USGS data.
As the above shows there are several sites with maps of the planets/satellites of our solar system on the Internet. In contrast, I have found very few sites with models of actual (as opposed to fictional) spacecraft so I recently started my own attempts to fix this by building a POV-Ray model of NASA's Cassini spacecraft.
I'm also interested in all kinds of 3D animations so I also added animation support to my renderer. I have created of few big animations, e.g. an approximately 2000 frame flyby of Jupiter and some of its satellites and a 1500 frame flight from the Earth outwards and then by the moon, a Saturn flyby, a Cassini Saturn orbit insertion animation, animations of Galileo satellite and Jupiter flybys etc. Further information on the animations can be found here. The animations are created with a companion program, a spline curve/transformation matrix generator. With this program I can define spline curves and/or mathematical functions, either from "scratch" or by combining previously created splines/functions. I can then use the resulting functions as either individual elements in transformation matrices or combine three of them into a 3D "path". The variable in these functions is usually time. The renderer then reads the resulting file of transformation matrices, one or many matrices per frame, and uses them to transform the 3D scene or individual parts of it. It can be specified which part to transform with each individual matrix and the 3D models are hierarchical giving many possibilities. All this stuff is specified in an input file containing commands resembling a (somewhat primitive) programming language.
If you don't understand the above and it looks complex the most probable reason is that it really is so...
Creating planetary maps
The planetary maps available here were created by me and are public, they were created from data available on the Internet and/or spacecraft imagery available on CDs from the National Space Science Data Center and improve on maps of the same subjects available elsewhere. But please note that the renderings are copyrighted by me (see the legal stuff page). I created these models because I was not satisfied with the ones available and I had the necessary data to create versions that are better suited for use in 3D renderings.
Usually I start with a map I do not like and replace parts of it with better data or I create a new map from scratch (it seems I usually end up creating them from scratch these days). I take one or more spacecraft images and use the geometric information embedded in these image files (they are in highly specialized formats) to project the images onto a cylindrical map. If no information on the viewing geometry is available it must be "reverse engineered" from the image and an existing map. The image files may also contain information on the illumination conditions. That information can be used to compensate for the different illumination in different areas of the image or between the many images. The compensation is done by assuming the image subject follows some empirical photometric function (for icy satellites like Europa a photometric function devised by Buratti works like magic but cloudy planets like Saturn are more difficult). I then further compensate for the illumination in Photoshop using (mainly) gradients and also remove the seams between the images that show up on the map. This results in a grayscale map. Finally I add color, either synthetic or from other images. There is more detailed information on this subject on some of the the individual map pages under my planetary maps page.
When creating the model of Saturn's rings I simply found some nice images where the rings filled the field of view, cleaned them up a bit and then did a single radial scan through the entire ring system and used the resulting intensity values. I finally edited them, setting the intensity to 0 (and transparency to 1) where I knew no ring material was present (i.e. gaps in the ring system).
In the future I will add more models here. Saturn's satellites, a better map of Europa possibly Triton are most likely, I'm not completely satisfied with the maps of them available now on the web.
And again finally, thanks to David Seal and others at NASA, to the US Geological Survey, Constantine Thomas, James Hastings-Trew, Doug Fortune and others for making all the stuff making this possible publicly available on the Internet (see my legal stuff/acknowledgements page for further info).
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