The Engineering Challenge

Unlike a conventional screen, the volcano model included:

• Sloped and elevated terrain
• A recessed crater
• Irregular outer boundaries
• Different depths between the model and the background wall

Basic keystone or four-corner correction could define the overall image area, but it could not align the content with all the internal contours of the model.

Projector positioning was equally important. Raised sections of the volcano could create shadows, while the model and background wall required different geometric adjustments. Digital warping could reshape the image, but it could not compensate for unsuitable projector angles or physical obstruction.

Why GeoBox M802EX Was Selected

M802EX is the dual-channel model in the GeoBox M800EX family. It can receive a source image, distribute the required portions to two projector outputs and apply independent geometry correction to each channel. The same product family also supports the use of projection-mapping patterns created and uploaded through the GWarp3 PC tool.

For the UNICAL installation, this allowed DOCONLINE to work with one complete visual composition rather than managing two entirely separate playback systems.

The architecture provided several practical advantages:

• Both projectors used the same source signal
• Separate media-player synchronisation was not required
• Image division could be refined during installation
• Projection geometry could be adjusted independently of content production
• Mapping and alignment settings could be stored in the GeoBox hardware

This last point is important for permanent installations. Once the mapping patterns and geometry settings have been saved in the unit, the PC used for configuration is no longer required for normal operation.

From the Physical Object to a Mapping Pattern

The M800EX projection-mapping procedure begins before any pattern is uploaded to the processor.

For an irregular object, the recommended method is to observe the target from the same position as the projector lens. A reference image can then be taken from that viewpoint and used to create a black-and-white mapping pattern representing the exact area where content should appear.

In practical terms, the workflow is:

1. Position the projector and establish the intended coverage.
2. Capture the physical object from the projector’s viewpoint.
3. Create a monochrome pattern based on the object’s visible silhouette.
4. Size the pattern according to the projector resolution and the portion of the projected area occupied by the object.
5. Upload the pattern into GeoBox through GWarp3.
6. Preview the result before saving it to the hardware.

This approach is different from using geometry correction alone.

Geometry correction reshapes the complete rectangular image. The mapping pattern defines where the source should remain visible and where it should be masked. Together, these two functions allow the image to follow both the position and the outline of an irregular physical object.

Building the Projection from the Outside In

Once the projectors and mapping patterns had been established, the geometry could be refined.

The M800EX setup procedure recommends completing alignment progressively, beginning with basic four-corner control and then moving to denser warp grids only when required. This prevents the installation engineer from introducing excessive local distortion before the overall image structure is correct.

1. Establish the Overall Projection Boundary

The first task was to place the projected image in the correct physical area.

At this stage, the engineers focused on:

• The outer boundary of the model
• The overall image size
• The relative positions of the two projector channels
• The boundary between the model and the background wall

The objective was not yet to match every ridge or crater detail.

2. Align the Major Terrain Features

After the overall boundary had been established, the engineers could progressively refine the internal geometry.

Only after these elements were stable did it make sense to correct smaller local details.

3. Refine the Mapping Pattern Position

The mapping pattern was then checked against the physical outline of the volcano.

If the pattern did not sit precisely over the intended object, its position could be refined through geometry correction. 

4. Complete the Two-Projector Relationship

Once both channels had been corrected individually, DOCONLINE could refine the scale, position and transition between them.

This order made troubleshooting more manageable. A remaining mismatch could be identified more clearly as:

• A projector-positioning issue
• A geometry issue
• A mapping-pattern issue
• A source-distribution issue