Adding Billboarding support to HLSL Sprite Shader in Unity - unity3d

Question

I have, for a while, been trying to wrangle HLSL to add support for billboarding 2D NPCs in think DOOM or Hexen: Beyond Heretic, but I just can't seem to figure it out, or may be missing something entirely.Full code snippet below:
Shader "Sprites/Bumped Diffuse both sides with Shadows & Chroma"
{
Properties
{
[PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
_BumpMap("Normalmap", 2D) = "bump" {}
_Color("Tint", Color) = (1,1,1,1)
[MaterialToggle] PixelSnap("Pixel snap", Float) = 0
_Cutoff("Alpha Cutoff", Range(0,1)) = 0.5
_ChromaKeyColour("Chroma Key Colour", Color) = (1,1,1,1)
_ChromaKeyHueRange("ChromaKey Hue Range", Float) = 0
_ChromaKeySaturationRange("ChromaKey Saturation Range", Float) = 0
_ChromaKeyBrightnessRange("ChromaKey Brightness Range", Float) = 0
_ChromaKeyNewColour("New Colour From Chroma", Color) = (1,1,1,1)
_ChromaKeyColour2("Chroma Key Colour", Color) = (1,1,1,1)
_ChromaKeyHueRange2("ChromaKey Hue Range", Float) = 0
_ChromaKeySaturationRange2("ChromaKey Saturation Range", Float) = 0
_ChromaKeyBrightnessRange2("ChromaKey Brightness Range", Float) = 0
_ChromaKeyNewColour2("New Colour From Chroma", Color) = (1,1,1,1)
_ChromaKeyColour3("Chroma Key Colour", Color) = (1,1,1,1)
_ChromaKeyHueRange3("ChromaKey Hue Range", Float) = 0
_ChromaKeySaturationRange3("ChromaKey Saturation Range", Float) = 0
_ChromaKeyBrightnessRange3("ChromaKey Brightness Range", Float) = 0
_ChromaKeyNewColour3("New Colour From Chroma", Color) = (1,1,1,1)
}
SubShader
{
Tags
{
"Queue" = "Transparent"
"IgnoreProjector" = "True"
"RenderType" = "TransparentCutOut"
"PreviewType" = "Plane"
"CanUseSpriteAtlas" = "True"
}
LOD 300
Cull Off
Lighting On
ZWrite Off
Fog { Mode Off }
CGPROGRAM
#pragma surface surf Lambert alpha vertex:vert addshadow alphatest:_Cutoff billboard
#pragma multi_compile DUMMY PIXELSNAP_ON
sampler2D _MainTex;
sampler2D _BumpMap;
fixed4 _Color;
fixed4 _ChromaKeyColour;
fixed4 _ChromaKeyNewColour;
float _ChromaKeyHueRange;
float _ChromaKeySaturationRange;
float _ChromaKeyBrightnessRange;
fixed4 _ChromaKeyColour2;
fixed4 _ChromaKeyNewColour2;
float _ChromaKeyHueRange2;
float _ChromaKeySaturationRange2;
float _ChromaKeyBrightnessRange2;
fixed4 _ChromaKeyColour3;
fixed4 _ChromaKeyNewColour3;
float _ChromaKeyHueRange3;
float _ChromaKeySaturationRange3;
float _ChromaKeyBrightnessRange3;
float _ScaleX;
struct Input
{
float2 uv_MainTex;
float2 uv_BumpMap;
fixed4 color : COLOR;
};
void vert(inout appdata_full v, out Input o)
{
#if defined(PIXELSNAP_ON) && !defined(SHADER_API_FLASH)
v.vertex = UnityPixelSnap(v.vertex);
#endif
float3 normal = v.normal;
float3 cameraToVertex = normalize(v.vertex.xyz - _WorldSpaceCameraPos.xyz);
v.normal = float3(0,1,1);
v.tangent = float4(1, 0, 0, 1);
UNITY_INITIALIZE_OUTPUT(Input, o);
o.color += _Color;
}
inline float3 ChromaKeyRGB2HSV(float3 rgb)
{
float4 k = float4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
float4 p = lerp(float4(rgb.bg, k.wz), float4(rgb.gb, k.xy), step(rgb.b, rgb.g));
float4 q = lerp(float4(p.xyw, rgb.r), float4(rgb.r, p.yzx), step(p.x, rgb.r));
float d = q.x - min(q.w, q.y);
float e = 1e-10;
return float3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}
inline float3 ChromaKeyHSV2RGB(float3 hsv)
{
float4 k = float4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
float3 p = abs(frac(hsv.xxx + k.xyz) * 6.0 - k.www);
return hsv.z * lerp(k.xxx, clamp(p - k.xxx, 0.0, 1.0), hsv.y);
}
inline float3 ChromaKeyCalcDiffrence(float4 col, float4 col_key)
{
float3 hsv = ChromaKeyRGB2HSV(col);
float3 key = ChromaKeyRGB2HSV(col_key);
return abs(hsv - key);
}
inline float3 ChromaKeyGetRange(float chromaKeyHueRange, float chromaKeySaturationRange, float chromaKeyBrightnessRange)
{
return float3(chromaKeyHueRange, chromaKeySaturationRange, chromaKeyBrightnessRange);
}
inline void ChromaKeyApplyCutout(float4 col, float4 key, float hueRange, float satRange, float briRange)
{
float3 d = ChromaKeyCalcDiffrence(col, key);
if (all(step(0.0, ChromaKeyGetRange(hueRange, satRange, briRange) - d))) discard;
}
inline void ChromaKeyApplyAlpha(inout float4 col, float4 key, float hueRange, float satRange, float briRange)
{
float3 d = ChromaKeyCalcDiffrence(col, key);
if (all(step(0.0, ChromaKeyGetRange(hueRange, satRange, briRange) - d))) discard;
col.a *= saturate(length(d / ChromaKeyGetRange(hueRange, satRange, briRange)) - 1.0);
}
inline void ChromaKeyApplyColour(inout float4 col, float4 key, float4 new_col, float hueRange, float satRange, float briRange)
{
float3 d = ChromaKeyCalcDiffrence(col, key);
if (all(step(0.0, ChromaKeyGetRange(hueRange, satRange, briRange) - d)))
{
float3 colHSV = ChromaKeyRGB2HSV(col.rgb);
float3 newColHSV = ChromaKeyRGB2HSV(new_col.rgb);
newColHSV.b *= colHSV.b;
col.rgb = ChromaKeyHSV2RGB(newColHSV);
}
}
void surf(Input IN, inout SurfaceOutput o)
{
fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * IN.color;
ChromaKeyApplyColour(c, _ChromaKeyColour, _ChromaKeyNewColour, _ChromaKeyHueRange, _ChromaKeySaturationRange, _ChromaKeyBrightnessRange);
ChromaKeyApplyColour(c, _ChromaKeyColour2, _ChromaKeyNewColour2, _ChromaKeyHueRange2, _ChromaKeySaturationRange2, _ChromaKeyBrightnessRange2);
ChromaKeyApplyColour(c, _ChromaKeyColour3, _ChromaKeyNewColour3, _ChromaKeyHueRange3, _ChromaKeySaturationRange3, _ChromaKeyBrightnessRange3);
o.Albedo = c.rgb;
o.Alpha = c.a;
o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));
o.Normal.z *= -1;
}
ENDCG
}
Fallback "Transparent/Cutout/Diffuse"
}
As far as I know I want to do this through the vertex part of the shader, but I'm not sure what I actually want to manipulate - the normal would make some sense but I am not sure.