Chaos Corona Forum
Chaos Corona for Cinema 4D => [C4D] Feature Requests => Topic started by: steppes on 2023-03-23, 07:55:49
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Hi!
There are two ways to interpret normal maps (Y up or Y down) and it is very hard to identify what kind of normal map ons has. You guys always say "flip Y", but this seems not always right.
I there a way to implement something in corona helping finding out what normal map is used?
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Knowing what to flip will come down to your eye and personal taste on how the normal map should look.
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Yep, unfortunately normal maps don't contain any information about how they were generated or what was chosen for the up/down directions or which axis is which color. This means there's no way for software to even make a 'guess' at what is correct, leaving it to the viewer to make sure that things expected to be indented or popping out are correctly looking indented or popping out.
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You can find some additional info here:
https://forum.corona-renderer.com/index.php?topic=39601.0
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ok, thanks!
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Proper normal maps with distinct features can be quite easily distinguished between OpenGL (+Y) and DirectX (-Y). Usually the former looks more correct to the eye, while the latter looks inverted. You can see good example of this here: https://www.texturecan.com/post/3/DirectX-vs-OpenGL-Normal-Map/ scroll to the examples with keyboard. This is not 100% reliable technique, as some normal maps can be hard to read and sometimes your mind may play tricks on you, but it's quite handy to know that you can quite effortlessly identify like 90% of good normal maps. I said "good", because this trick almost completely does not work on trash normal maps, that are derived from single images and in other fake ways.