Single Default Cube Exported Wrongly under Blender 4.3

[Richardn2002]

System Information

• Ogre Version: 14.3.4
• Operating System / Platform: Arch Linux x86_64, 6.13.5-arch1-1
• Blender Version: 4.3.2

Detailed description

Above is what ogre-meshviewer shows for the mesh exported from the default Blender project: just a cube. I assume this is not expected?

This looks like some mesh winding order problem to me, and I tried investigating a bit myself:

• Blender 3 to 4 does have some Python API changes related to meshes (pre 3.5 to 3.5, 3.5 to 3.6, 3.6 to 4.0), but they do not seem related to me. But I am no professional on this.
• There are 8 vertices in a cube, but in the resulting file there are 24 vertices in total, with each vertex replicating for 3 times. Is this intended?

To replicate, just open Blender, close the startup dialogue, and proceed to export. But anyways here are the mesh and the material:

Mesh:

<?xml version="1.0" encoding="UTF-8"?>
<mesh>
    <sharedgeometry vertexcount="24">
        <vertexbuffer colours_diffuse="False" normals="true" positions="true" tangent_dimensions="0" tangents="False" texture_coords="1">
            <vertex>
                <position x="1.000000" y="1.000000" z="-1.000000"/>
                <normal x="0.000000" y="1.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="1.000000"/>
                <normal x="0.000000" y="1.000000" z="-0.000000"/>
                <texcoord u="0.875000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="1.000000" z="1.000000"/>
                <normal x="0.000000" y="1.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="1.000000"/>
                <normal x="0.000000" y="0.000000" z="1.000000"/>
                <texcoord u="0.375000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="1.000000"/>
                <normal x="0.000000" y="0.000000" z="1.000000"/>
                <texcoord u="0.625000" v="0.000000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="1.000000"/>
                <normal x="0.000000" y="0.000000" z="1.000000"/>
                <texcoord u="0.375000" v="0.000000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="1.000000"/>
                <normal x="-1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="1.000000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="-1.000000"/>
                <normal x="-1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="0.750000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="-1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="0.750000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="0.000000" y="-1.000000" z="-0.000000"/>
                <texcoord u="0.125000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="1.000000"/>
                <normal x="0.000000" y="-1.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="1.000000"/>
                <normal x="0.000000" y="-1.000000" z="-0.000000"/>
                <texcoord u="0.125000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="1.000000" z="1.000000"/>
                <normal x="1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="1.000000"/>
                <normal x="1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="0.000000" y="0.000000" z="-1.000000"/>
                <texcoord u="0.375000" v="0.750000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="1.000000" z="-1.000000"/>
                <normal x="0.000000" y="0.000000" z="-1.000000"/>
                <texcoord u="0.625000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="0.000000" y="0.000000" z="-1.000000"/>
                <texcoord u="0.375000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="-1.000000"/>
                <normal x="0.000000" y="1.000000" z="-0.000000"/>
                <texcoord u="0.875000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="1.000000" z="1.000000"/>
                <normal x="0.000000" y="0.000000" z="1.000000"/>
                <texcoord u="0.625000" v="0.250000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="1.000000"/>
                <normal x="-1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="1.000000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="-1.000000" z="-1.000000"/>
                <normal x="0.000000" y="-1.000000" z="-0.000000"/>
                <texcoord u="0.375000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="1.000000" y="1.000000" z="-1.000000"/>
                <normal x="1.000000" y="0.000000" z="-0.000000"/>
                <texcoord u="0.625000" v="0.500000"/>
            </vertex>
            <vertex>
                <position x="-1.000000" y="1.000000" z="-1.000000"/>
                <normal x="0.000000" y="0.000000" z="-1.000000"/>
                <texcoord u="0.625000" v="0.750000"/>
            </vertex>
        </vertexbuffer>
    </sharedgeometry>
    <submeshes>
        <submesh material="Material" operationtype="triangle_list" use32bitindexes="False" usesharedvertices="true">
            <faces count="12">
                <face v1="0" v2="1" v3="2"/>
                <face v1="3" v2="4" v3="5"/>
                <face v1="6" v2="7" v3="8"/>
                <face v1="9" v2="10" v3="11"/>
                <face v1="12" v2="13" v3="14"/>
                <face v1="15" v2="16" v3="17"/>
                <face v1="0" v2="18" v3="1"/>
                <face v1="3" v2="19" v3="4"/>
                <face v1="6" v2="20" v3="7"/>
                <face v1="9" v2="21" v3="10"/>
                <face v1="12" v2="22" v3="13"/>
                <face v1="15" v2="23" v3="16"/>
            </faces>
        </submesh>
    </submeshes>
    <submeshnames>
        <submesh index="0" name="Material"/>
    </submeshnames>
</mesh>

Material:

// generated by blender2ogre 0.9.0 on 2025-03-13 12:46:42
material Material {
    receive_shadows off
    technique {
        pass {
            scene_blend alpha_blend
            cull_hardware none
            depth_write off
            diffuse 0.8 0.8 0.8 1.0
            specular 0.5 0.0 0 0 0

            // additional maps - requires RTSS
            rtshader_system {
                lighting_stage metal_roughness
            }
        }
    }
}

blender2ogre.log

2025-03-13 12:46:42 [ INFO] * Target path: <REDACTED>/cube
2025-03-13 12:46:42 [ INFO] * Target file name: blender2ogre.scene
2025-03-13 12:46:42 [ INFO] * Blender version: 4.3.2 (release; Linux)
2025-03-13 12:46:42 [ INFO] * Processing Scene: blender2ogre, path: <REDACTED>/cube
2025-03-13 12:46:42 [ INFO] * Processing Materials
2025-03-13 12:46:42 [WARNING] Roughness input is not connected
2025-03-13 12:46:42 [ INFO] * Exporting root node: Cube 
2025-03-13 12:46:42 [ INFO] * Generating: Cube.mesh.xml
2025-03-13 12:46:42 [ INFO]   - Vertices: 8
2025-03-13 12:46:42 [ INFO]   - Loop triangles: 12
2025-03-13 12:46:42 [ INFO] * Writing shared geometry
2025-03-13 12:46:42 [ INFO] - Done at 0.02 seconds
2025-03-13 12:46:42 [ INFO] * Writing submeshes
2025-03-13 12:46:42 [ INFO] - Done at 0.02 seconds
2025-03-13 12:46:42 [ INFO] - Created Cube.mesh.xml at 0.02 seconds
2025-03-13 12:46:42 [ INFO] - Created Cube.mesh in total time 0.02 seconds
2025-03-13 12:46:42 [ INFO] * Exporting root node: Light 
2025-03-13 12:46:42 [ INFO] * Exporting root node: Camera 
2025-03-13 12:46:42 [ INFO] - Exported Ogre Scene: <REDACTED>/cube/blender2ogre.scene 
2025-03-13 12:46:42 [ INFO] - Done at 0.03 seconds

OgreXMLConverter.log

12:46:42: XMLMeshSerializer reading mesh data from <REDACTED>/cube/Cube.mesh.xml...
12:46:42: Reading geometry...
12:46:42: Geometry done...
12:46:42: Reading submeshes...
12:46:42: Submeshes done.
12:46:42: Reading mesh names...
12:46:42: Mesh names done.
12:46:42: XMLMeshSerializer import successful.
12:46:42: MeshSerializer writing mesh data to stream <REDACTED>/cube/Cube.mesh...
12:46:42: File header written.
12:46:42: Writing mesh data...
12:46:42: Writing submesh...
12:46:42: Submesh exported.
12:46:42: Exporting bounds information....
12:46:42: Bounds information exported.
12:46:42: Exporting submesh name table...
12:46:42: Submesh name table exported.
12:46:42: Mesh data exported.
12:46:42: MeshSerializer export successful.

[Richardn2002]

Ah, removing cull_hardware none solves the issue. Now investigating how this line gets into the final outputs.

Update: is about io_ogre/ogre/material.py#L194 this line and deprecation of Material.blend_method

[paroj]

exporting the default cube with blender 4.3 does not write any transparency for me

[paroj]

There are 8 vertices in a cube, but in the resulting file there are 24 vertices in total, with each vertex replicating for 3 times. Is this intended?

this is correct, see:
https://paroj.github.io/gltut/Illumination/Tut09%20Mesh%20Topology.html

[Richardn2002]

The PR I sent fixes the transparency problem for me (by not writing cull_hardware none to the .material file(s)). Probably we are bumping into some kind of "undefined behavior" of Blender by depending on a deprecated variable.