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Last active December 14, 2015 08:49
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How to project spherical clipmaps onto a sphere and apply texture heightmaps.
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gistfile1.md

  • Based on the distance between the camera and planet determine how many clipmaps will be created and at what detail level.

  • Get camera vector in planet's local space.

  • Find point planet where the line between the camera and planet's center intersects its surface.

  • Convert that point into phi and theta.

  • Based on phi and theta generate metatextures for each clipmap level.

    • The top level clipmap will simply be the coarsest texture, with a x axis twice as wide as the y. The x axis will be mapped from -PI to PI with 0 at the prime meridian. The y axis will be mapped from 0 to PI with 0 at the N. Pole.
    • Need a way to determine how wide the metatextures will be based on their theta. A texture at PI/2 theta will only need to be as wide and tall as the diameter of the circle. But if the circle's diameter encompasses a pole, it needs to be as wide as the top level texture.

  • Update the material for the circle.

  • On the GPU rotate the vertex to its correct phi and theta and displace it along its normals by the amount in the texture.

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