I would be most grateful if someone could advise me on the error of my ways. Using Google Sketchup a DAE model was built and is shown in Slide1.png attached. It appears to have no obvious defects in the geometry shown. However, a colleague of mine altered this basic model to include ‘components’ which translate in Collada 1.4.1 as recursive nodes. I have checked the geometry modifications and it appears that all transformations used are Translations and therefore no modifications would be made to the Normal coordinates. All the geometry arrays look fine so it should be viewed ok without anything missing. However, what I get is slide2mod.png and slide3mod.png (I had to chop them a little to get them into this query so they view a smaller area). These slides show in several cases that one side of a building is missing and the inside wall of the opposite face is visible. If you rotate the scene and look at the same buildings you will see that the inside face of the previously invisible walls are now visible. Sorry if this sounds confusing but it best to look at the three images and hopefully it may be more clear what I mean. I have checked this now for over a month and am no clearly what could cause this problem. It seems clear to me that the geometry works out ok but there is a visiblity issue. There are no different lighting changes or materials or anything like that.
I would be most grateful for any comments on this issue as I am quite perplexed by it now and find no way of resolving this except to explode in Google Sketchup so that there is little recursion in the model.