how to add tangent and binormal to surface shader

Unity Engine
1

for add add tangent and binormal to surface shader , but find something error .
it only says : too many texture interpolators would be used for forwardbase pass at line 9

how to add tangent and binormal to surface shader, what is the correct way to do this ,
is any sample code here in unity?

here is my code :
Shader “Custom/sur” {
Properties {
_MainTex (“Base (RGB)”, 2D) = “white” {}
}
SubShader {
Tags { “RenderType”=“Opaque” }
LOD 200

CGPROGRAM
#pragma surface surf LambertA vertex:vert

sampler2D _MainTex;

struct Input {
float2 uv_MainTex;
half3 normal_input;
half3 tangent_input;
half3 binormal_input;
};
struct SurfaceOutputEx{
half3 Albedo;
half3 Normal;
half3 Emission;
half3 Gloss;
half Specular;
half Alpha;
half3 normal_input;
half3 tangent_input;
half3 binormal_input;
};

void vert(inout appdata_full i, out Input o){
half4 p_normal =mul(float4(i.normal,0.0f),_World2Object);
half4 p_tangent =mul(_Object2World,i.tangent);

half3 normal_input =normalize(p_normal.xyz);
half3 tangent_input=normalize(p_tangent.xyz);
half3 binormal_input =cross(p_normal.xyz,p_tangent.xyz);

o.normal_input =normal_input;
o.tangent_input =tangent_input ;
o.binormal_input =binormal_input ;
}

void surf (Input IN, inout SurfaceOutputEx o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex);
o.Albedo = c.rgb ;
o.Alpha = c.a;
o.normal_input =IN.normal_input;
o.tangent_input =IN.tangent_input ;
o.binormal_input =IN.binormal_input ;
}

inline half4 LightingLambertA (SurfaceOutputEx s , half3 lightDir, half3 viewDir, half atten)
{
half3 h =normalize(lightDir+viewDir);
half3 b =s.binormal_input;
half diff = max (0, dot (s.Normal, lightDir));

half4 c;
c.rgb = s.Albedo * _LightColor0.rgb * (diff * atten * 2) ;
c.a = s.Alpha;
return c ;
}

ENDCG
}
FallBack “Diffuse”
}

2

I don’t know surface shaders very well, but it’s not a binormal. It’s a bitangent.

3

The terms are pretty much interchangeable. Technically it is, indeed, a bitangent, but it’s generally referred to as a binormal.

You’ll need to add #pragma target 3.0 to your shader to get around the interpolator limit.

You’ll also want to multiply your binormal by the w component of the tangent (which stores handedness);

half3 binormal_input =cross(p_normal.xyz,p_tangent.xyz) * i.tangent.w;

1 Like
4

The way to compute the binormal can be found in the cginclude UnityCG.cginc (found in your Editor/Data/CGIncludes folder):

float3 binormal = cross( v.normal, v.tangent.xyz ) * v.tangent.w;

The error you got, “too many texture interpolators” is indicative of having too much data in your Input struct. Like James said, you can use #pragma target 3.0 to allow for more data, or you can get creative with how you pack things into your input struct.

5

Stop propagating the problem. The term hasn’t been misused long enough, and it’s not widely used enough, for it to be hard to fix the issue.

6

Doesn’t the UnityCG.cginc file refer to it as the binormal? If you think it should be called something different, you might want to take it up with Aras or Rej.

7

Haha, fair point.

I think it’s widely used enough that you’ll have a fight on your hands to change it now, but I’ll try :stuck_out_tongue:

8

thanks Farfarer , you are right
thanks for help .