#ShaderGraph Sky - Pushing vertices to the far plane!

1 messages · Page 1 of 1 (latest)

lean canopy
#

Hello!
I'm just trying to use a shader to push all vertices to the far clip plane, so an object renders behind everything else. Very much just copying this. (First image is the example)
I want to do it within ShaderGraph, but ShaderGraph outputs vertex positions in Object space. My simple hack solve was to try to do it in a custom node, and convert from clip space back to object space before returning- which half worked.

//UNITY_SHADER_NO_UPGRADE
#ifndef VERTEXPUSHFARCLIP_INCLUDED
#define VERTEXPUSHFARCLIP_INCLUDED

float4x4 GetHClipToWorldMatrix()
{
    return UNITY_MATRIX_I_VP; 
}
float3 TransformHClipToObject(float4 positionCS)
{
    return mul(GetWorldToObjectMatrix(), mul(GetHClipToWorldMatrix(), positionCS)).xyz;
}

// the main function:
void TransformVerts_float(float3 In_OS, out float3 Out_OS)
{
    Out_OS = float3(0, 0, 1);
    
    float4 clipPos = TransformObjectToHClip(In_OS);
    // 2. apply transformation
#if UNITY_REVERSED_Z
        // when using reversed-Z, make the Z be just a tiny
        // bit above 0.0
        clipPos.z = 1.0e-9f;
#else
    // when not using reversed-Z, make Z/W be just a tiny
    // bit below 1.0
    clipPos.z = clipPos.w - 1.0e-6f;
#endif
    
    // 3. return to object space
    Out_OS = TransformHClipToObject(clipPos);

}
#endif //VERTEXPUSHFARCLIP_INCLUDED

I've attached a video of what that looks like!
As you can see, it kinda works until you start getting closer up to it - and it also halves the size of the mesh.
I suspect I'm screwing something up with the matrix math, but I'm not totally sure what.

Any thoughts would be massively appreciated!

infinite-sky.png image.png
#

ShaderGraph - Pushing vertices to the far plane!

lean canopy
#

ShaderGraph Sky - Pushing vertices to the far plane!

lean canopy
#

I have tried this kind of hack workaround to do it in world space, and it sorta-works, but floating point precision means that for high far clip plane distances, you often end up with a hole in the back - and I think that's just a silly thing to deal with when I could be doing this directly in homogenous clip space or NDC space? But the real problem I guess at the end there is having to convert back to object space at all.

image.png