# Converting normals from right handed to left handed

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How do I go about doing this? Do I have to use some rotation matrix? Thanks

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are you talking about the vertex ordering? or taking normals for a right handed coordinate system and changing them to a left handed one?

vertex ordering is simple. just negate the normal.

going to different handed coordinate systems, just multiply the normal by the same matrix you're using to convert the points to and from the system.

Tim

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Quote:
 Original post by timware you talking about the vertex ordering? or taking normals for a right handed coordinate system and changing them to a left handed one?vertex ordering is simple. just negate the normal.going to different handed coordinate systems, just multiply the normal by the same matrix you're using to convert the points to and from the system. Tim

I am talking about taking the normals and changing them. I am not multiplying the points by anything, I am just negating the z-axis. This works for points, but not vectors it seems (unless there is something else wrong of course!).

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it depends on the types of transformations applied to the object, if you have any non rigid transformaitons, you can't simply multiply the normals with the same matrix you multiply points with. you need to multiply it by the transpose of the inverse of your transform matrix. or is it the inverse of the transpose? I can't remember. try both.

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timw

And both will work, inverse transpose and transpose inverse both work fine.

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