/** * @private */ vec2 cordic(float angle) { // Scale the vector by the appropriate factor for the 24 iterations to follow. vec2 vector = vec2(6.0725293500888267e-1, 0.0); // Iteration 1 float sense = (angle < 0.0) ? -1.0 : 1.0; // float factor = sense * 1.0; // 2^-0 mat2 rotation = mat2(1.0, sense, -sense, 1.0); vector = rotation * vector; angle -= sense * 7.8539816339744828e-1; // atan(2^-0) // Iteration 2 sense = (angle < 0.0) ? -1.0 : 1.0; float factor = sense * 5.0e-1; // 2^-1 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 4.6364760900080609e-1; // atan(2^-1) // Iteration 3 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 2.5e-1; // 2^-2 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 2.4497866312686414e-1; // atan(2^-2) // Iteration 4 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.25e-1; // 2^-3 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.2435499454676144e-1; // atan(2^-3) // Iteration 5 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 6.25e-2; // 2^-4 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 6.2418809995957350e-2; // atan(2^-4) // Iteration 6 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 3.125e-2; // 2^-5 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 3.1239833430268277e-2; // atan(2^-5) // Iteration 7 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.5625e-2; // 2^-6 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.5623728620476831e-2; // atan(2^-6) // Iteration 8 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 7.8125e-3; // 2^-7 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 7.8123410601011111e-3; // atan(2^-7) // Iteration 9 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 3.90625e-3; // 2^-8 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 3.9062301319669718e-3; // atan(2^-8) // Iteration 10 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.953125e-3; // 2^-9 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.9531225164788188e-3; // atan(2^-9) // Iteration 11 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 9.765625e-4; // 2^-10 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 9.7656218955931946e-4; // atan(2^-10) // Iteration 12 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 4.8828125e-4; // 2^-11 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 4.8828121119489829e-4; // atan(2^-11) // Iteration 13 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 2.44140625e-4; // 2^-12 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 2.4414062014936177e-4; // atan(2^-12) // Iteration 14 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.220703125e-4; // 2^-13 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.2207031189367021e-4; // atan(2^-13) // Iteration 15 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 6.103515625e-5; // 2^-14 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 6.1035156174208773e-5; // atan(2^-14) // Iteration 16 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 3.0517578125e-5; // 2^-15 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 3.0517578115526096e-5; // atan(2^-15) // Iteration 17 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.52587890625e-5; // 2^-16 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.5258789061315762e-5; // atan(2^-16) // Iteration 18 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 7.62939453125e-6; // 2^-17 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 7.6293945311019700e-6; // atan(2^-17) // Iteration 19 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 3.814697265625e-6; // 2^-18 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 3.8146972656064961e-6; // atan(2^-18) // Iteration 20 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.9073486328125e-6; // 2^-19 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 1.9073486328101870e-6; // atan(2^-19) // Iteration 21 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 9.5367431640625e-7; // 2^-20 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 9.5367431640596084e-7; // atan(2^-20) // Iteration 22 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 4.76837158203125e-7; // 2^-21 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 4.7683715820308884e-7; // atan(2^-21) // Iteration 23 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 2.384185791015625e-7; // 2^-22 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; angle -= sense * 2.3841857910155797e-7; // atan(2^-22) // Iteration 24 sense = (angle < 0.0) ? -1.0 : 1.0; factor = sense * 1.1920928955078125e-7; // 2^-23 rotation[0][1] = factor; rotation[1][0] = -factor; vector = rotation * vector; // angle -= sense * 1.1920928955078068e-7; // atan(2^-23) return vector; } /** * Computes the cosine and sine of the provided angle using the CORDIC algorithm. * * @name czm_cosineAndSine * @glslFunction * * @param {float} angle The angle in radians. * * @returns {vec2} The resulting cosine of the angle (as the x coordinate) and sine of the angle (as the y coordinate). * * @example * vec2 v = czm_cosineAndSine(czm_piOverSix); * float cosine = v.x; * float sine = v.y; */ vec2 czm_cosineAndSine(float angle) { if (angle < -czm_piOverTwo || angle > czm_piOverTwo) { if (angle < 0.0) { return -cordic(angle + czm_pi); } else { return -cordic(angle - czm_pi); } } else { return cordic(angle); } }