Transform node in shadergraph to cg/hlsl

Hi! I have a shader that I need to use in this project, but it’s done in shadergraph and the project is in the built-in standard pipeline (and can’t change), so I’m rewriting it in code. I’m finding trouble with the Transform nodes, specially with the Tangent->Object (type: direction) and World->Object (type: direction). Anyone knows how to write them in code for the standard pipeline or where i can find that information?

World to object is relatively straight forward.

float3 objectDir = mul((float3x3)unity_WorldToObject, worldDir);

Tangent to object is a little more work, and depends on how your shader is written. The short version being the shader needs to have the world space normal, tangent, and bitangent (aka binormal) vectors available in the fragment shader. For Surface Shaders you need to add a few things to the Input struct to get access to those vectors. Specifically float3 worldNormal; and INTERNAL_DATA. Then you can call WorldNormalVector(IN, vector) to transform a tangent vector into world space. With that you can construct a tangent to world matrix, and from that use the world to object transform above.

struct Input {
  float2 uv_MainTex; // etc
  float3 worldNormal;

// inside surf function    
float3 worldDir = WorldNormalVector(IN, tangentDir);
float3 objectDir = mul((float3x3)unity_WorldToObject, worldDir);

If you’re writing a vertex fragment shader you will already be creating a matrix to transform the tangent space normal maps into world space for lighting. So you’d use that and then the world to object transform.