Problem Solving: 2D Billboard Sprites clipping into 3D environment

Unity Engine
71

Sorry to necro this post but here in the future I am trying to port Ben’s code to Shadergraph. I have written a port of his code for a Custom Function node, but the behaviour is not the same. I’ve poured over it repeatedly and cannot find a single mistake or error, yet the behaviour is not correct.

Do you see any mistakes?

Pictured: Left: my code, Right: Ben’s code.

bad axies

inputs
inputs1230×1186 142 KB

inline float rayPlaneIntersection(float3 rayDir, float3 rayPos, float3 planeNormal, float3 planePos)
{
    float denom = dot(planeNormal, rayDir);
    denom = max(denom, 0.000001); // avoid divide by zero
    float3 diff = planePos - rayPos;
    return dot(diff, planeNormal) / denom;
}

void VerticalZDepth_float(
    float3 vertexPos,           // object-space vertex position
    float4x4 ObjectToWorld,     // Object-to-World matrix
    float4x4 Matrix_V,          // View matrix
    float4x4 Matrix_P,          // Projection matrix
    float4x4 Matrix_I_V,        // Inverse View matrix
    float4x4 Matrix_VP,         // ViewProjection matrix
    float3 WorldSpaceCameraPos, // World-space camera position
    out float4 position         // modified clip-space position (xyzw)
)
{
    // billboard mesh towards camera
    float3 vpos = mul((float3x3) ObjectToWorld, vertexPos);
    float4 worldCoord = float4(ObjectToWorld[0][3], ObjectToWorld[1][3], ObjectToWorld[2][3], 1.0);
    float4 viewPos = mul(Matrix_V, worldCoord) + float4(vpos, 0.0);
    float4 clipPos = mul(Matrix_P, viewPos);
    
    // calculate distance to vertical billboard plane seen at this vertex's screen position
    float3 planeNormal = normalize(float3(Matrix_V[2][0], 0.0, Matrix_V[2][2]));
    float3 planePoint = float3(ObjectToWorld[0][3], ObjectToWorld[1][3], ObjectToWorld[2][3]);
    float3 rayStart = WorldSpaceCameraPos;    
    float3 invViewPos = mul(Matrix_I_V, float4(viewPos.xyz, 1.0)).xyz;
    float3 rayDir = -normalize(invViewPos - rayStart);    
    float dist = rayPlaneIntersection(rayDir, rayStart, planeNormal, planePoint);
    
    // calculate the clip space z for vertical plane
    float4 planeOutPos = mul(Matrix_VP, float4(rayStart + rayDir * dist, 1.0));
    float newPosZ = (planeOutPos.z / planeOutPos.w) * clipPos.w;
    
    // use the closest clip space z
    #if defined(UNITY_REVERSED_Z)
    clipPos.z = max(clipPos.z, newPosZ);
    #else
    clipPos.z = min(clipPos.z, newPosZ);
    #endif

    position = clipPos;
}

My only lead is my suspicion that the tables are built differently, and that index positions as well as rows and columns do not directly equate the way I have written here:

float3 planePoint = unity_ObjectToWorld._m03_m13_m23;
float3 planePoint = float3(ObjectToWorld[0][3], ObjectToWorld[1][3], ObjectToWorld[2][3]);

Are these not equivalent? How would I determine if they are or are not equivalent? How do I make them equivalent?