godot/modules/mobile_vr/mobile_vr_interface.h

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/*  mobile_vr_interface.h                                                */
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#ifndef MOBILE_VR_INTERFACE_H
#define MOBILE_VR_INTERFACE_H

#include "servers/xr/xr_interface.h"
#include "servers/xr/xr_positional_tracker.h"

/**
	@author Bastiaan Olij <mux213@gmail.com>

	The mobile interface is a native VR interface that can be used on Android and iOS phones.
	It contains a basic implementation supporting 3DOF tracking if a gyroscope and accelerometer are
	present and sets up the proper projection matrices based on the values provided.

	We're planning to eventually do separate interfaces towards mobile SDKs that have far more capabilities and
	do not rely on the user providing most of these settings (though enhancing this with auto detection features
	based on the device we're running on would be cool). I'm mostly adding this as an example or base plate for
	more advanced interfaces.
*/

class MobileVRInterface : public XRInterface {
	GDCLASS(MobileVRInterface, XRInterface);

private:
	bool initialized = false;
	XRInterface::TrackingStatus tracking_state;
	Basis orientation;

	// Just set some defaults for these. At some point we need to look at adding a lookup table for common device + headset combos and/or support reading cardboard QR codes
	float eye_height = 1.85;
	uint64_t last_ticks = 0;

	real_t intraocular_dist = 6.0;
	real_t display_width = 14.5;
	real_t display_to_lens = 4.0;
	real_t oversample = 1.5;

	real_t k1 = 0.215;
	real_t k2 = 0.215;
	real_t aspect = 1.0;

	/*
		logic for processing our sensor data, this was originally in our positional tracker logic but I think
		that doesn't make sense in hindsight. It only makes marginally more sense to park it here for now,
		this probably deserves an object of its own
	*/
	Vector3 scale_magneto(const Vector3 &p_magnetometer);
	Basis combine_acc_mag(const Vector3 &p_grav, const Vector3 &p_magneto);

	int mag_count = 0;
	bool has_gyro = false;
	bool sensor_first = false;
	Vector3 last_accerometer_data;
	Vector3 last_magnetometer_data;
	Vector3 mag_current_min;
	Vector3 mag_current_max;
	Vector3 mag_next_min;
	Vector3 mag_next_max;

	///@TODO a few support functions for trackers, most are math related and should likely be moved elsewhere
	float floor_decimals(const float p_value, const float p_decimals) {
		float power_of_10 = pow(10.0f, p_decimals);
		return floor(p_value * power_of_10) / power_of_10;
	};

	Vector3 floor_decimals(const Vector3 &p_vector, const float p_decimals) {
		return Vector3(floor_decimals(p_vector.x, p_decimals), floor_decimals(p_vector.y, p_decimals), floor_decimals(p_vector.z, p_decimals));
	};

	Vector3 low_pass(const Vector3 &p_vector, const Vector3 &p_last_vector, const float p_factor) {
		return p_vector + (p_factor * (p_last_vector - p_vector));
	};

	Vector3 scrub(const Vector3 &p_vector, const Vector3 &p_last_vector, const float p_decimals, const float p_factor) {
		return low_pass(floor_decimals(p_vector, p_decimals), p_last_vector, p_factor);
	};

	void set_position_from_sensors();

protected:
	static void _bind_methods();

public:
	void set_eye_height(const real_t p_eye_height);
	real_t get_eye_height() const;

	void set_iod(const real_t p_iod);
	real_t get_iod() const;

	void set_display_width(const real_t p_display_width);
	real_t get_display_width() const;

	void set_display_to_lens(const real_t p_display_to_lens);
	real_t get_display_to_lens() const;

	void set_oversample(const real_t p_oversample);
	real_t get_oversample() const;

	void set_k1(const real_t p_k1);
	real_t get_k1() const;

	void set_k2(const real_t p_k2);
	real_t get_k2() const;

	virtual StringName get_name() const override;
	virtual uint32_t get_capabilities() const override;

	virtual TrackingStatus get_tracking_status() const override;

	virtual bool is_initialized() const override;
	virtual bool initialize() override;
	virtual void uninitialize() override;

	virtual Size2 get_render_target_size() override;
	virtual uint32_t get_view_count() override;
	virtual Transform3D get_camera_transform() override;
	virtual Transform3D get_transform_for_view(uint32_t p_view, const Transform3D &p_cam_transform) override;
	virtual CameraMatrix get_projection_for_view(uint32_t p_view, real_t p_aspect, real_t p_z_near, real_t p_z_far) override;
	virtual Vector<BlitToScreen> commit_views(RID p_render_target, const Rect2 &p_screen_rect) override;

	virtual void process() override;

	MobileVRInterface();
	~MobileVRInterface();
};

#endif // !MOBILE_VR_INTERFACE_H