Geometry template in Ninja cannot correctly apply or display `transformationMatrix`, `material`, and `texture`

[SavageChigga]

🧩 Geometry template in Ninja cannot correctly apply or display transformationMatrix, material, and texture

📘 Background

In geographic scene modeling, objects such as trees are often represented using geometry templates to save space and resources.
According to the CityJSON 2.0.1 specification, a template object can include a material member.

Figure 1. Example from CityJSON specification showing template support for the material member.

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🧪 Test Setup and Validation

1. Base Model Validation

• A single tree model with branch and trunk was created using a CityObject.
• Both material and texture were displayed correctly in Ninja.
• The model passed cjval validation (The file is valid).

Figure 2. cjval validation result of the base tree object.

2. Geometry Template Test

• The same tree was restructured using a geometry template for reuse.
• The model was visualized correctly, but its transformationMatrix, material, and texture were not applied correctly.
• The data file also passed cjval validation (The file is 100% valid!).

Figure 3. cjval validation result of the template-based file.

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📁 Test Data Description

✅ TreeDemo.city.json

• A single tree model represented as a SolitaryVegetationObject.
• Serves as the baseline for verifying correct rendering of material and texture.
• Validated successfully using cjval.
• Data file: TreeDemo.city.json

Figure 4. Default tree model.

Figure 5. Tree model with different materials.

Figure 6. Tree model with applied textures.

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🧩 IssueDemo.city.json

• Contains two cube objects (using CityObjects) and two tree objects (using geometry templates).
• Both tree models share the same geometry template but reference different transformation indices.
• Each tree consists of a trunk and a branch component.
• Data file: IssueDemo.city.json

Figure 7. Comparison between cube (CityObject) and tree (geometry template) models.

both files use the same Texture resources:

1. wood.jpg
2. brick.jpg
3. Trunk_MAT.jpeg
4. Branch_MAT.png

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⚠️ Problem Description

1. transformationMatrix not applied correctly

• In Ninja, geometry templates only display correctly with the default matrix.
• Any modification (translation, rotation, scaling) causes the object to disappear.
• Example: scaling or offsetting the trunk of the second tree makes it invisible.

"transformationMatrix": [
    10.0, 0.0, 0.0, 0.0,
    0.0, 10.0, 0.0, 0.0,
    0.0, 0.0, 10.0, 0.0,
    0.0, 0.0, 0.0, 1.0
]

Figure 8. Object disappears when a non-default transformationMatrix is applied.

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2. material not displayed correctly

• Cube objects display different materials correctly.
• Tree objects (using geometry templates) disappear when material is assigned.

Figure 9. Cube rendered correctly, tree model disappears when material applied.

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3. texture not displayed correctly

• Cube objects display textures correctly.
• Tree objects (geometry templates) show no visible texture changes.

Figure 10. Cube shows texture properly, tree model unaffected.

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💡 Summary

Geometry template objects in Ninja cannot correctly apply or display:

• transformationMatrix
• material
• texture

All tested files are 100% valid according to cjval.

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❓Questions

1. What might cause Ninja to fail applying these attributes (transformationMatrix, material, texture) to geometry template objects?
2. Is there a known fix, configuration, or workaround to correctly render geometry templates with these properties?