From f60bed509a7e416c155bcd35d5151bca65eaa190 Mon Sep 17 00:00:00 2001
From: Justin Berger <j.david.berger@gmail.com>
Date: Wed, 21 Mar 2018 11:20:34 -0600
Subject: IMU research

---
 src/survive_imu.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 src/survive_imu.c

(limited to 'src/survive_imu.c')

diff --git a/src/survive_imu.c b/src/survive_imu.c
new file mode 100644
index 0000000..6fb3076
--- /dev/null
+++ b/src/survive_imu.c
@@ -0,0 +1,89 @@
+#include "survive_imu.h"
+#include "linmath.h"
+#include "survive_internal.h"
+#include <survive_imu.h>
+
+void survive_imu_tracker_set_pose(SurviveIMUTracker *tracker, SurvivePose *pose) { tracker->pose = *pose; }
+
+static const int imu_calibration_iterations = 100;
+
+static void RotateAccel(LinmathVec3d rAcc, const SurvivePose *pose, const LinmathVec3d accel) {
+	quatrotatevector(rAcc, pose->Rot, accel);
+	scale3d(rAcc, rAcc, 2.);
+	LinmathVec3d G = {0, 0, -1};
+	add3d(rAcc, rAcc, G);
+}
+static SurvivePose iterate_position(const SurvivePose *pose, const LinmathVec3d vel, double time_diff,
+									const PoserDataIMU *pIMU) {
+	SurvivePose result = *pose;
+
+	FLT acc_mul = time_diff * time_diff / 2;
+	LinmathVec3d rAcc = {0};
+	RotateAccel(rAcc, pose, pIMU->accel);
+	scale3d(rAcc, rAcc, acc_mul);
+
+	LinmathVec3d gyro;
+
+	for (int i = 0; i < 3; i++) {
+		result.Pos[i] += time_diff * vel[i] + rAcc[i] * 9.8;
+		gyro[i] = time_diff / 2 * pIMU->gyro[i];
+	}
+
+	LinmathEulerAngle curr, next;
+	quattoeuler(curr, pose->Rot);
+	add3d(next, curr, gyro);
+	quatfromeuler(result.Rot, next);
+
+	return result;
+}
+
+static void iterate_velocity(LinmathVec3d result, const SurvivePose *pose, const LinmathVec3d vel, double time_diff,
+							 PoserDataIMU *pIMU) {
+	scale3d(result, vel, .99999);
+	LinmathVec3d rAcc = {0};
+	RotateAccel(rAcc, pose, pIMU->accel);
+	scale3d(rAcc, rAcc, time_diff);
+	add3d(result, result, rAcc);
+}
+
+void survive_imu_tracker_integrate(SurviveObject *so, SurviveIMUTracker *tracker, PoserDataIMU *data) {
+	if (tracker->last_data.timecode == 0) {
+		if (tracker->last_data.datamask == imu_calibration_iterations) {
+			tracker->last_data = *data;
+			return;
+		}
+
+		tracker->last_data.datamask++;
+
+		tracker->updir[0] += data->accel[0] / imu_calibration_iterations;
+		tracker->updir[1] += data->accel[1] / imu_calibration_iterations;
+		tracker->updir[2] += data->accel[2] / imu_calibration_iterations;
+		return;
+	}
+
+	for (int i = 0; i < 3; i++) {
+		tracker->updir[i] = data->accel[i] * .10 + tracker->updir[i] * .90;
+	}
+
+	FLT up[3] = {0, 0, 1};
+	FLT pose_up[3] = {0, 0, 1};
+	quatrotatevector(pose_up, tracker->pose.Rot, tracker->updir);
+
+	FLT time_diff = (data->timecode - tracker->last_data.timecode) / (FLT)so->timebase_hz;
+
+	SurvivePose t_next = iterate_position(&tracker->pose, tracker->current_velocity, time_diff, data);
+
+	LinmathVec3d v_next;
+	iterate_velocity(v_next, &tracker->pose, tracker->current_velocity, time_diff, data);
+
+	tracker->pose = t_next;
+	scale3d(tracker->current_velocity, v_next, 1);
+
+	tracker->last_data = *data;
+
+	FLT tmp[3];
+	ApplyPoseToPoint(tmp, &tracker->pose, up);
+
+	printf("[%f, %f, %f] [%f, %f, %f]\n", tracker->pose.Pos[0], tracker->pose.Pos[1], tracker->pose.Pos[2], tmp[0],
+		   tmp[1], tmp[2]);
+}
-- 
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