terrain

Here are the results of some experiments I did with terrain rendering. I can render fairly large crumpled spheres, made to look like planets. The ones on this page are made up of around 4 million triangles. They are rendered entirely in software. The lighting is per vertex and the polygons are untextured.

First these are some images of the planets as seen from the surface. This first image is fractally generated terrain using some 'dr seuss' parameters. ( click on the images to enlarge them )

These are images using digital elevation map (DEM) data from the us geological survey.

Here is an image of the planet as seen from space, with no atmosphere. You can see the planet is kind of small, as the mountains poke up off the surface pretty high. Notice the river basin in the middle of that big continent. This is US geological survey data.

Here are some images showing the yet unfinished polygon culling algorithm. It removes triangles from low detail areas. It does not work properly yet. See how it leaves T junctions and cracks.

These planets are made using 2 square height fields, one for each hemisphere. The heightfields are organized using a quad tree. I have a cheap algorithm for wrapping these two height fields on a sphere with low distortion almost everywhere. The first image puts the lowest distortion part of the mapping in the front. See how nice and even it is? The second image shows the worst distortion, along the equator. The maximum distortion is 5:1. That is the largest triangle on the sphere is 5 times the size of the smallest. This mapping algorithm is very cheap, I calculate the 3d coordinate of every point from a height field value and its position in the quad tree.