camera.cpp

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#include "camera.hpp"
 
#include <math.h>
#include <assert.h>
 
#include "attitude-utils.hpp"
#include "decimal.hpp"
 
namespace lost {
 
Vec2 Camera::SpatialToCamera(const Vec3 &vector) const {
    // can't handle things behind the camera.
    assert(vector.x > 0);
    // TODO: is there any sort of accuracy problem when vector.y and vector.z are small?
 
    decimal focalFactor = focalLength/vector.x;
 
    decimal yPixel = vector.y*focalFactor;
    decimal zPixel = vector.z*focalFactor;
 
    return { -yPixel + xCenter, -zPixel + yCenter };
}
 
Vec3 Camera::CameraToSpatial(const Vec2 &vector) const {
    assert(InSensor(vector));
 
    // isn't it interesting: To convert from center-based to left-corner-based coordinates is the
    // same formula; f(x)=f^{-1}(x) !
    decimal xPixel = -vector.x + xCenter;
    decimal yPixel = -vector.y + yCenter;
 
    return {
        1,
        xPixel / focalLength,
        yPixel / focalLength,
    };
}
 
bool Camera::InSensor(const Vec2 &vector) const {
    // if vector.x == xResolution, then it is at the leftmost point of the pixel that's "hanging
    // off" the edge of the image, so vector is still in the image.
    return vector.x >= 0 && vector.x <= xResolution
        && vector.y >= 0 && vector.y <= yResolution;
}
 
decimal FovToFocalLength(decimal xFov, decimal xResolution) {
    return xResolution / DECIMAL(2.0) / DECIMAL_TAN(xFov/2);
}
 
decimal FocalLengthToFov(decimal focalLength, decimal xResolution, decimal pixelSize) {
    return DECIMAL_ATAN(xResolution/2 * pixelSize / focalLength) * 2;
}
 
decimal Camera::Fov() const {
    return FocalLengthToFov(focalLength, xResolution, 1.0);
}
 
}