I have a model made in blender, which I've exported as a collada file. When loading it in my game engine, I get the result as shown in picture A. The code used to calculate the tangents are shown in picture B. If I set the tangents to something like (1,1,1) I get a much more smooth result but it gets very blocky in the places where there's supposed to be fine details (on high poly models). If I export the model to obj-format and load it in my engine through another pipeline, which uses the same code for calculating the tangents, the result is perfect. Does collada order the vertices in a strange order? I'm confused here and pretty much stuck. any tips would be appreciated.

I'll start by showing what happens when I load a simple box with 8 vertices, a texture and a normal map, this is collada format as well.

Here's two boxes, the exact same model, using the exact same shader and textures, the only difference is that the faulty one is imported as a collada and the correct one is imported as .obj

Here's another strange thing, the vertex positions in the collada file and .obj file doesn't match at all, there's not even any mention in the collada file of the vertices that are supposed to be at -0.004383! perhaps this discrepancy can be a part of the problem? Do anyone know why this is the case?

Nope, it's triangulated. I even tried to triangulate the model manually, same result (and same values in the exported file, so the triangulation is working) :(

We can start with the simple box-models, I'm sure that if I can get them to work the rest will fall into place. Though I suspect that the problem isn't with the models, collada seems to order vertices and texture UV's in a very different way than .obj-files, and this could possibly mess up my calculations (though I have no idea on how to fix it).

The .obj-model is working, the .dae (collada) model is not. They are using the exact same base model in blender.

.obj: https://minfil.com/V5X4Q1bcoc/testbox_obj (Swedish site, just press ‘ladda ner’, means download)

.dae: https://minfil.com/LaX2Q7b1o9/boxmodel_dae

Thanks a bunch for the help, I hope that this is the actual issue, and I will investigate it more tomorrow now that I have some clues. Though I'm not sure what you mean by sewn and unsewn UV-edges, if you have any resources I could sift through to learn about it that would be great (otherwise I'll just google about it, no worries).

Thanks again for the help and I will report back if I can (or can't) solve it tomorrow (it's getting late here).

I'm stumped. Here's what information I could gather, throwing it out there in case someone can solve this, because I sure can't.

I made a model that is fully triangulated, a box. In the .dae/collada file I get 72 uv values (s and t values), which would correspond to 36 vertices (3 for every triangle face in the cube). In the .obj file I get 48 uv values (s and t values), which would correspond to 24 vertices (2 for every triangle in the cube, or 4 for every face).

When manually printing out the vertex positions, uv-values, normals and tangents I get these results (numbering added to some value lists):

.obj file: https://minfil.com/ZbU7Y5b5oa/obj_rtf

.dae file: https://minfil.com/l9V4Y1b9oa/collada_rtf

As can be seen the result here as well, after being loaded by the engine, contains a different amount of vertices and uv-positions as could be expected.

The tangent calculations are based on the .obj file format, and applied without any other consideration to the .dae based model (the code can be seen in my first post). This is probably wrong, and there's probably some modifications that needs to be done here, but I have no clue as to how to proceed here). I'll restate that the normal mapping is working for the .obj files, and not working for the .dae files, so the basis of the tangent calculations should be correct.