<t>I've found that my graphic card drivers where not the latest available, so I upgraded them. <br/>
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The problem went away if I do not use the textures for the walls. If I use only colors, 3D is working well. <br/>
But when using textures, the problem reappeared : from the left upper corner ...

<t>Hello, <br/>
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When trying to make walls, the 3D view is following like expected. <br/>
But when moving around in 3D other lines and triangles from the corners of the 3D view are put on screen. Sometimes they cover completely the design. <br/>
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Other problem is when using a texture for ...