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repair the starfield renderer

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Stephen Birarda 2014-04-08 17:31:30 -07:00
parent 638b49e47d
commit ab3a9af6bf
1 changed files with 49 additions and 2 deletions
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51
interface/src/starfield/renderer/Renderer.h
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@ -9,6 +9,54 @@
// See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
#ifndef __interface__starfield__renderer__Renderer__
#define __interface__starfield__renderer__Renderer__
#include "starfield/Config.h"
#include "starfield/data/InputVertex.h"
#include "starfield/data/Tile.h"
#include "starfield/data/GpuVertex.h"
#include "starfield/renderer/Tiling.h"
//
// FOV culling
// ===========
//
// As stars can be thought of as at infinity distance, the field of view only
// depends on perspective and rotation:
//
// _----_ <-- visible stars
// from above +-near-+ - -
// \ / |
// near width: \ / | cos(p/2)
// 2sin(p/2) \/ _
// center
//
//
// Now it is important to note that a change in altitude maps uniformly to a
// distance on a sphere. This is NOT the case for azimuthal angles: In this
// case a factor of 'cos(alt)' (the orbital radius) applies:
//
//
// |<-cos alt ->| | |<-|<----->|->| d_azi cos(alt)
// |
// __--* | --------- -
// __-- * | | | ^ d_alt
// __-- alt) * | | | v
// --------------*- | ------------- -
// |
// side view | tile on sphere
//
//
// This lets us find a worst-case (Eigen) angle from the center to the edge
// of a tile as
//
// hypot( 0.5 d_alt, 0.5 d_azi cos(alt_absmin) ).
//
// This angle must be added to 'p' (the perspective angle) in order to find
// an altered near plane for the culling decision.
//
namespace starfield {
class Renderer {
@ -90,5 +138,4 @@ namespace starfield {
}
#endif
#endif