Particle Custom Vertex Streams World Position Shader

GridShaderUnlit.shader

// All Credit goes to
// http://harrygodden.com/blog/?article=vrc-gridsnap

Shader "Terri/GridShaderUnlit" {
    Properties {
        _MainTex("Texture", 2 D) = "white" {}
        _GridSize("Grid Size", Float) = 1.0
        _SnapDistance("Snap Distance", Float) = 2.0
    }
    SubShader {
        Tags {
            "RenderType" = "Opaque"
        }
        LOD 100

        Pass {
            CGPROGRAM
            # pragma vertex vert
            # pragma fragment frag
            # pragma multi_compile_particles
            # pragma multi_compile_fog
            # include "UnityCG.cginc"

            struct appdata_t {
                float4 vertex: POSITION;
                float4 texcoords: TEXCOORD0;
            };

            struct v2f {
                float4 vertex: SV_POSITION;
                float2 texcoord: TEXCOORD0;
                UNITY_FOG_COORDS(1)
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            float _GridSize;
            float _SnapDistance;

            v2f vert(appdata_t v) {
                v2f o;
                o.vertex = v.vertex;
                o.texcoord = TRANSFORM_TEX(v.texcoords, _MainTex);

                // Get world position of object
                float3 ObjectWorldPosition = v.vertex.xyz;

                // Snap object origin to grid
                float3 SnappedOrigin = float3(floor(((ObjectWorldPosition.x / _GridSize) + 0.5)) * _GridSize,
                    floor(((ObjectWorldPosition.y / _GridSize) + 0.5)) * _GridSize,
                    floor(((ObjectWorldPosition.z / _GridSize) + 0.5)) * _GridSize);

                // Calculate snap offset
                float3 VertexOffset = ObjectWorldPosition - SnappedOrigin;

                // Check if within snap distance
                if (length(VertexOffset) < _SnapDistance) {
                    // Apply offset
                    o.vertex.xyz -= VertexOffset;
                }

                o.vertex = UnityObjectToClipPos(o.vertex);
                UNITY_TRANSFER_FOG(o, o.vertex);
                return o;
            }

            fixed4 frag(v2f i): SV_Target {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.texcoord);
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDCG
        }
    }
}