Triple-monitor angle and bezels, as geometry

A triple-screen rig is not three copies of one field-of-view number. From the eye point, the center panel and two rotated side panels occupy different rays. The angle decides where the outer edges land; the bezels decide how much of the scene is hidden at each join. A useful model must therefore locate the panels, trace the visible endpoints, and keep the missing seam intervals separate from the active image.

The chord-tangent rule

The suggested side angle uses the flat-chord-tangent mounting convention: yaw = 2 × atan(cabinet width ÷ (2 × eye distance)). Cabinet width is visible chord width plus one bezel on each side. The result is the angle that one complete flat cabinet subtends at the centered eye. Apply that yaw from straight to each side monitor. Treat it as a repeatable starting convention, not an optimization, universal preference, or exact tangency condition for every curved surface.

The rule is useful because it connects the hinge geometry to quantities you can measure. A wider cabinet or shorter eye distance produces a larger subtended angle and therefore a more aggressive wrap. A narrower cabinet or longer distance produces a smaller angle. On curved monitors, the calculator still applies the recommendation to the measured chord; curvature changes the traced surface and visible spans, not the name or basis of this mounting convention.

You do not have to use the recommendation. Choose manual yaw and enter the actual angle from straight if the mount is already fixed, if clearances control the layout, or if you are documenting a different convention. The results then describe that measured rig and show the difference from nominal when a chord-tangent comparison exists. If the cabinet subtends more than 90°, the tool cannot offer a recommendation within its permitted range, but a valid manual layout may still be calculable.

Measure the angle consistently

“60-degree triples” is ambiguous unless the zero direction is named. In this calculator, zero means coplanar with the center screen; the displayed side angle is the rotation from straight, toward the viewer. Measure the panel chord or cabinet face in a top view. Do not use the interior angle between monitors without conversion: an interior hinge angle and a yaw-from-straight value are supplements under common measuring setups.

Measure both sides instead of assuming the mount is symmetric. The current model accepts identical panels and symmetric yaw, so record any mismatch before averaging. A large left-right difference is information about the physical rig, not noise to conceal. Align the visible center of the middle panel to the eye point first, because the ray model assumes the eye is centered on that panel.

Why bezel width is not cosmetic

The bezel input is one side of one monitor: the distance from the active image edge to the cabinet edge. At a seam, the right bezel of one cabinet meets the left bezel of the next, so identical monitors create a physical gap of 2 × bezel per side. The ray interval behind that gap is real scenery, but it is occluded by cabinet material. Correct bezel handling preserves the world’s scale across the interruption rather than squeezing all scenery into the visible pixels.

The calculator reports seam occlusion as an angle. If you provide horizontal resolution, it also estimates hidden pixels from the seam width relative to active width. For a 597.7 mm active panel, 7 mm per-side bezels, and 2560 horizontal pixels per monitor, the 14 mm seam corresponds to about 60 hidden pixels at each join. Those pixels are an equivalent accounting device for a bezel-corrected span; they are not physical pixels under the plastic.

Native game modes expose geometry for the same underlying reason. iRacing’s official triple setup asks for bezel width, monitor width, viewing distance, and angle and provides a three-projection option (official iRacing triple setup). ACC’s official v1.8 notes refer to bezel-line fixes inside its named Triple Screen rendering mode (official ACC v1.8 notes). These game-specific facts come from the conventions dataset; they illustrate why seams and panel orientation belong in rendering geometry rather than in a single multiplied FOV.

Visible envelope versus active coverage

visibleEnvelope is the full angular reach from the outer visible edge of the left panel to the outer visible edge of the right panel. activeImageCoverage subtracts the two angular seam occlusions. The envelope answers “how far around the eye do the displays reach?” Coverage answers “how much of that interval emits image?” The two should not be collapsed, because a larger bezel can reduce coverage without moving the outer edges very much.

centerSpan is a third quantity: the angle of the middle active image alone. Multiplying it by three assumes three angular intervals can be added without regard to rotation or seam location. The ray model instead transforms each side panel around its hinge and measures its endpoints from the eye. This remains valid for manual yaw, where three times the center span can be especially misleading.

What WRAPS_BEHIND_EYE means

The warning WRAPS_BEHIND_EYE appears when the full visible envelope exceeds 180°. Plainly: at least one outer visible edge lies behind the plane passing left-to-right through the eye. The screen may still be physically in front of your face and the calculation may remain defined; “behind” refers to the direction of the sight ray relative to the eye plane, not to the entire monitor being behind the seat.

The calculator returns the result with a warning because a wrap slightly beyond 180° is still a meaningful description of a layout. Inspect usability, renderer limits, head clearance, and whether the entered yaw and curve orientation match reality. The warning is not an automatic instruction to reduce the angle. More severe cases—folded geometry, a non-monotonic curved arc that endpoint tracing would under-report, or panel edges reaching the eye plane—do not produce a numeric result.

The prefilled example uses three 708.5 mm-wide, 1000R panels, 7 mm bezels, 650 mm center distance, and recommended chord-tangent yaw. Its visible envelope is about 183.7°, so it demonstrates the warning without hiding the numeric result.

Open the prefilled wrapped-triples example

Audit the physical rig

Record active width, cabinet width, bezel per side, center distance, left and right yaw, and curve radius. Check that bezel was not entered as the total seam; doing so doubles the occlusion. Check that angle was measured from straight rather than copied as an interior hinge angle. Finally, compare the calculator’s assumptions on the methodology page with the mount in front of you. The result is only as specific as the geometry you actually supplied.

External sources

• iRacing: Setting up three monitors — official example of width, bezel, distance, angle, and three projections
• ACC PC update v1.8 — official Triple Screen rendering-mode and bezel-line context