Boomer labs was show casing a cool new map plugin for 3dsMax that uses curvature.

Check it out here: https://vimeo.com/124072533

So I got inspired to play around with curvature in a real-time shader.

I knew about ddx and ddy and then found my way to a cool webGL shader by Evan Wallace.

`http://madebyevan.com/shaders/curvature/`

Plugging this into ShaderFX inside 3dsMax and a few tweaks later we get:

```
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`I used a custom code node inside ShaderFX, so below is the code I ended up using.`

```
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`I noticed that the curvature colors flip around on the other side of the world axis (so the back side of the model). I didn't have the time to figure out why that is yet.`

```
float ComputeCurvature( float3 vertex, float3 normal, float strength)
{
float3 n = normalize(normal);
float3 dx = ddx(n);
float3 dy = ddy(n);
float3 xneg = n - dx;
float3 xpos = n + dx;
float3 yneg = n - dy;
float3 ypos = n + dy;
float depth = length(vertex);
float curvature = (cross(xneg, xpos).y - cross(yneg, ypos).x) * strength / depth;
return curvature;
}
struct CurvatureCalcOutput
{
float curvature;
float negative;
float positive;
float3 color;
};
CurvatureCalcOutput CurvatureCalcFunc(float3 vertex_pos, float3 normal, float strength)
{
CurvatureCalcOutput OUT;
OUT.curvature = ComputeCurvature(vertex_pos, normal, strength);
OUT.positive = clamp(-OUT.curvature, 0, 1);
OUT.negative = clamp(OUT.curvature, 0, 1);
OUT.color = float3(0,1,0);
OUT.color = lerp( OUT.color, float3(1,0,0), OUT.negative);
OUT.color = lerp( OUT.color, float3(0,0,1), OUT.positive);
return OUT;
}
```

```
```

Did you ever figure out the world axis flip thing?

ReplyDeleteCould this work in Maya?

ReplyDeleteWorks just fine in Maya

ReplyDeleteThis comment has been removed by the author.

ReplyDeleteHi. Can you consider to update this code? I'm receive a message where the code is invalid or too old. Thanks

ReplyDelete