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/**
* Computes a 3x3 rotation matrix that transforms vectors from an ellipsoid's east-north-up coordinate system
* to eye coordinates. In east-north-up coordinates, x points east, y points north, and z points along the
* surface normal. East-north-up can be used as an ellipsoid's tangent space for operations such as bump mapping.
* <br /><br />
* The ellipsoid is assumed to be centered at the model coordinate's origin.
*
* @name czm_eastNorthUpToEyeCoordinates
* @glslFunction
*
* @param {vec3} positionMC The position on the ellipsoid in model coordinates.
* @param {vec3} normalEC The normalized ellipsoid surface normal, at <code>positionMC</code>, in eye coordinates.
*
* @returns {mat3} A 3x3 rotation matrix that transforms vectors from the east-north-up coordinate system to eye coordinates.
*
* @example
* // Transform a vector defined in the east-north-up coordinate
* // system, (0, 0, 1) which is the surface normal, to eye
* // coordinates.
* mat3 m = czm_eastNorthUpToEyeCoordinates(positionMC, normalEC);
* vec3 normalEC = m * vec3(0.0, 0.0, 1.0);
*/
mat3 czm_eastNorthUpToEyeCoordinates(vec3 positionMC, vec3 normalEC)
{
vec3 tangentMC = normalize(vec3(-positionMC.y, positionMC.x, 0.0)); // normalized surface tangent in model coordinates
vec3 tangentEC = normalize(czm_normal3D * tangentMC); // normalized surface tangent in eye coordiantes
vec3 bitangentEC = normalize(cross(normalEC, tangentEC)); // normalized surface bitangent in eye coordinates
return mat3(
tangentEC.x, tangentEC.y, tangentEC.z,
bitangentEC.x, bitangentEC.y, bitangentEC.z,
normalEC.x, normalEC.y, normalEC.z);
}
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12 entries across 12 versions & 1 rubygems