As everyone who has tried the FSX DX10 preview knows, there are problems with flashing textures. This is particularly the case at airports where sections of the tarmac often flash.
Someone on AVSIM (sorry I don’t recall who) very cleverly noticed that it only happened at airports with one texture type for runways surfaces Tarmac/Concrete. It didn’t occur at airports with both types. There is therefore a long winded fix possible to edit all 30K airports and add a small square of both surface types somewhere inconspicuous.
But why does it happen and is there a simpler fix?
Here is Bristol Airport (note that the scenery is not default its UK2000 free.)
Look at the runway ahead of the plane. It is flashing from black to grey. Yuk!
Its interesting at this point to try pausing. When inside the Cessna – pausing stops the grey/black changes – it freezes with what you see when you hit . The tower view behaves similarly but the spotter plane view behaves differently when paused – the changes continue?!
Setting the locked frame rate to 12 (its lowest) and viewing from outside and above you can see that it isn’t simply toggling between two images either. Different frames have different overlaps between the grey and tarmac textures. The grey shapes are not simple triangles either. There is also evidence of combing at the boundaries.
Now using the Intel GPA what do we find?
In the left frame the whole runway is painted in erg 176
The same erg in the second frame (176) uses the same texture but doesn’t paint the whole runway…
In the second frame the grey portion is painted in erg 174 thus
The rest of the runway gets painted in 176
In the first frame in erg 174 uses the same light grey texture but paints a different part of the runway. Note that if you zoom in there is another section on the left hand side in front of the white markings which is light grey in the first frame and dark in the second – so for that area the flashing is reversed. There isn’t a good and bad frame – its different areas in each.
Going back to the second frame and setting the Intel GPA to show highlight the wireframe – we see that before the draw we had the light texture and it looks like the vertices cover the whole runway – so what goes wrong? Its almost as if the runway texture has become see through in parts? There do not seem to be any vertices that delimit the area where it goes wrong?
Have we learnt anything? Sadly not really. As far as I can see from the Intel tool the DX10 commands appear identical and seem to refer to the same buffers. Is something going wrong interpolating the pixels of the two layers?
Perhaps we need to study those two drawcalls in more detail?