What Is the Gonion-to-Mouth Line in FaceIQ Labs' Harmony Analysis?
The Gonion-to-Mouth Line is a FaceIQ Labs side-view Harmony measurement of the vertical difference between the constructed jaw corner (gonion) and the mouth corner, calculated as (constructed gonion y − mouth-corner y) × photo scale. A negative value means the jaw corner sits above mouth-corner level; a positive value means below.
Key facts
- Formula: (constructed gonion y − mouth-corner y) × photo scale.
- Negative result: the jaw-line intersection is above mouth-corner level. Positive result: it is below mouth-corner level.
- The jaw corner is an intersection of extended jaw lines, not a single marked dot.
- Smiling moves the mouth reference used in the measurement.
- Millimeter values are estimates based on an assumed 190 mm hairline-to-chin height, not calibrated physical measurements.
- It is a FaceIQ photographic construction; the cited Farkas et al. (2005) study does not validate this exact formula or its scoring range.
- It is a side-view measurement in the Harmony pillar, and FaceIQ Labs standardizes side photos to the Frankfort horizontal plane during landmarking.
- Worked example: 10 units below the mouth corner at 0.2 estimated mm per unit gives +2 mm; this is not a target range.
What does the Gonion-to-Mouth Line measure?
The Gonion-to-Mouth Line is a FaceIQ Labs side-view Harmony measurement of the vertical difference between the constructed jaw corner (gonion) and the mouth corner. FaceIQ Labs calculates it as (constructed gonion y − mouth-corner y) × photo scale, showing how high or low the jaw corner sits relative to the mouth.
How do I read a negative or positive Gonion-to-Mouth Line result?
- In FaceIQ Labs' Gonion-to-Mouth Line, a negative value means the jaw-line intersection is above mouth-corner level.
- A positive value means the jaw-line intersection is below mouth-corner level.
- The sign convention describes how FaceIQ Labs reports its result.
- Example values in the guide are not target ranges.
Why does the Gonion-to-Mouth Line matter?
FaceIQ Labs uses the Gonion-to-Mouth Line because it locates the jaw corner within the height of the face. Two jaws with a similar corner angle can have different vertical positions relative to the mouth, so this measurement captures a difference that the corner angle alone does not.
What does a worked example of the Gonion-to-Mouth Line look like?
In FaceIQ Labs' worked example for the Gonion-to-Mouth Line, a jaw intersection 10 units below the mouth corner at 0.2 estimated mm per unit gives +2 mm. The example only explains the calculation. It is not a target range and is not a measurement of the schematic shown in the guide.
How does FaceIQ Labs find the jaw corner, and what affects the result?
FaceIQ Labs' Gonion-to-Mouth Line uses an intersection of extended jaw lines rather than a single marked jaw-corner dot. Smiling moves the mouth reference, which changes the mouth-corner level the jaw corner is compared against. FaceIQ Labs also standardizes side photos to the Frankfort horizontal plane during landmarking.
How accurate are the millimeter values in the Gonion-to-Mouth Line?
The millimeter values in FaceIQ Labs' Gonion-to-Mouth Line are estimates, not calibrated physical measurements. FaceIQ Labs scales the photo using an assumed 190 mm hairline-to-chin height, so the conversion from photo units to millimeters rests on an assumption rather than a physical reference measured on the person.
Is the Gonion-to-Mouth Line clinically validated?
No. FaceIQ Labs describes the Gonion-to-Mouth Line as a FaceIQ photographic construction. Clinical profile analysis provides context, but the cited work, Farkas et al. (2005), does not validate this exact landmark formula or its scoring range. Score weights and reference ranges are model settings, and the cited papers do not collectively validate the scoring system.
What research does FaceIQ Labs cite for the Gonion-to-Mouth Line?
FaceIQ Labs cites one source for the Gonion-to-Mouth Line: Farkas et al. (2005), 'International anthropometric study of facial morphology in various ethnic groups/races'. It documents variation in facial dimensions across sampled populations. Descriptive measurements explain variation; they do not establish an attractiveness score.
Which other FaceIQ Labs measurements cover the same jaw region?
- FaceIQ Labs groups the Gonion-to-Mouth Line, a side-view measurement within the Harmony pillar, with related jaw-region Harmony guides:
- Gonial Angle
- Mandibular Plane Angle
- Ramus to Mandible Ratio
- Chin Position Relative to the Frankfort Plane
Frequently asked questions
Is the Gonion-to-Mouth Line measured from the front or side photo?
It is a side-view measurement. FaceIQ Labs standardizes side photos to the Frankfort horizontal plane during landmarking.
Does smiling affect the Gonion-to-Mouth Line?
Yes. FaceIQ Labs notes that smiling moves the mouth reference, which changes the mouth-corner level used in the calculation.
What does a negative Gonion-to-Mouth Line value mean?
A negative value means the jaw-line intersection is above mouth-corner level. A positive value means it is below mouth-corner level.
Is the jaw corner a single marked point?
No. The app uses an intersection of extended jaw lines, not simply a single marked jaw-corner dot.
Why are the millimeter values only estimates?
FaceIQ Labs scales the photo using an assumed 190 mm hairline-to-chin height, so the values are estimates rather than calibrated physical measurements.
Is the +2 mm example a target range?
No. The example of a jaw intersection 10 units below the mouth corner at 0.2 estimated mm per unit explains the calculation only.