I've long been bothered by the behaviour of glass which has a coloured tint under varying lighting angle. Take for instance the green glazing on the B25's upper windscreen. When this glass is down-sun its green tint is brighter, and when up-sun it's darker and less 'colour-pure.' This arises from the dependence upon the ambient lighting, principally the Sun.
I've found a way to partly ameliorate this notable change in tinted glass appearance. It involves cloning said glass and reversing the surface normals for this second texture. In this way we have a texture which is brightest when up-sun superimposed with another texture which is brightest when down-sun. These two balance each other out.
However, there remains a bit of a fly in the ointment. When the glazing is oriented midway between the up- and down-sun directions both textures are midway between their light and dark aspects. This could be rectified by cloning additional glass and assigning surface normals as appropriate for the 'side lighting' orientation. But in the end, for reasonably good evenness of transition over all lighting angles it would require to have 6 overlapping textures, for the 3 mutually perpendicular axes.
But with just 2 overlapping textures, which at least balance at the hemisphere level, the improved cement is considerable, with the full range of bright/dark reduced to half. If you're familiar with the rectification of AC current for DC power supplies, you'll see why. The full sinusoidal wave of brightness (voltage) variation has, for example the dark (negative) side mirrored to the bright (positive) side. So instead of a sine wave weaving between +1 and -1 we have a 'bump wave' bouncing between +1 and 0.
I've started applying this to some armored glass which I want to have subtly tinted greenish.
I'd like to know of anyone has a better approach to this business of handling glass tinting that would not involve an extra, cloned mesh for that glass. I suppose I could experiment with the Shine parameter, which I've so far felt might not be appropriate for twilight/night if it remains too colorful. I know that using the .mat file parameter tfBendAdd is problematic in that different maps (particularly inntge case of winter vs summer) can have different ambient lighting settings which really have a big impact.
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Topic: About tinted glass and lighting (Read 1196 times)
