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I'm trying to make a directional map out of curves based on their direction. I thought of using the curve tangent node, but the result is not quite the same and the baked result doesn't work as intended when plugged into the tangent input for anisotropy

This is what a direction map should look like (source)

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And this is what I get when I use the curve tangent node

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In maya, it is possible to get a direction map by using the Tangent VCamera or the Surface Tangent Dpdv Texture . I couldn't find any information for any of that in blender

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Here is the node setup I used

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So my question is, what am I doing wrong, what should I change in order to get a functioning direction map

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  • $\begingroup$ The bottom picture, left curve, doesn't seem to have a $z$ (blue) component. So it is more or less horizontal. The upper picture clearly has a blue component. So it is vertical. This is of course assuming, that you display $x$ as red, $y$ as green and $z$ as blue, which is the standard way, because both $xyz$ order is the most common, RGB order for color is the most common and mapping one to other directly is also the most common. So why your curves are colored differently? Because they have different shape, "move" in different directions. $\endgroup$
    – Markus von Broady
    Commented Feb 8 at 10:09
  • $\begingroup$ Keep in mind various software uses different coordinate systems and often $y$ is the vertical coordinate, not $z$ as in Blender. $\endgroup$
    – Markus von Broady
    Commented Feb 8 at 10:10
  • $\begingroup$ @Chris I just added the blend file including more informations $\endgroup$
    – Alex
    Commented Feb 8 at 11:06
  • $\begingroup$ @MarkusvonBroady I assume blender reads curve tangent differently than maya (which is commonly used to make flow maps), but even though it doesn't seem to fit any of the examples I can find online For example: thefrontdev.co.uk/static/36f01b0f4678223cc054d3fbb09a5b88/b327b/… $\endgroup$
    – Alex
    Commented Feb 8 at 11:21
  • $\begingroup$ Maya is $y$-up. Also, Blender by default displays negative numbers as black, so you want to map the normalized direction from $[<-1, -1, -1>, <1, 1, 1>]$ range to $[<0, 0, 0>, <1, 1, 1>]$ by multiplying by $0.5$ and then adding $<0.5, 0.5, 0.5>$ $\endgroup$
    – Markus von Broady
    Commented Feb 8 at 11:27

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