I’m using GPU instancing with a mesh particle shader. The particle system is attached to an object whose parent has been translated and scaled, so the Scaling Mode of the particle system is set to Hierarchy to keep everything aligned. In Unity 2018.2 this shader works just fine, but in 2018.3 and 2019.1 the scaling is broken. Best I can tell it seems to be applying the resizing factor twice resulting in particles that rapidly become far too small or too large as I scale objects. The particles are still positioned correctly, it’s solely that their size is wrong. I have an equivalent shader that doesn’t use GPU instancing and the scaling works fine with it in each Unity version so I’m fairly confident the GPU instancing is the problem. Unfortunately I’m terrible at shaders so I was hoping someone might be able to help me fix this or to let me know if this is a bug in Unity that I should report.
Here’s the broken shader code;
Shader "VUE/Voxel Standard Particle" {
Properties {
_Color ("Color", Color) = (1,1,1,1)
_MainTex ("Albedo (RGB)", 2D) = "white" {}
_Glossiness ("Smoothness", Range(0,1)) = 0.5
_Metallic ("Metallic", Range(0,1)) = 0.0
_ZOffset ("Z Buffer Offset", Float) = 0
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 200
Offset [_ZOffset], [_ZOffset]
CGPROGRAM
// Physically based Standard lighting model, and enable shadows on all light types
// And generate the shadow pass with instancing support
#pragma surface surf Standard nolightmap nometa noforwardadd keepalpha fullforwardshadows addshadow vertex:vert
// Enable instancing for this shader
// See https://docs.unity3d.com/Manual/PartSysInstancing.html for more information about particle instancing.
#pragma multi_compile_instancing
#pragma instancing_options procedural:vertInstancingSetup
#pragma exclude_renderers gles
#include "UnityStandardParticleInstancing.cginc"
sampler2D _MainTex;
struct Input {
float2 uv_MainTex;
fixed4 vertexColor;
};
fixed4 _Color;
half _Glossiness;
half _Metallic;
void vert (inout appdata_full v, out Input o)
{
UNITY_INITIALIZE_OUTPUT(Input, o);
vertInstancingColor(o.vertexColor);
vertInstancingUVs(v.texcoord, o.uv_MainTex);
}
void surf (Input IN, inout SurfaceOutputStandard o) {
// Albedo comes from a texture tinted by color
fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * IN.vertexColor * _Color;
o.Albedo = c.rgb;
// Metallic and smoothness come from slider variables
o.Metallic = _Metallic;
o.Smoothness = _Glossiness;
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}
And here’s the equivalent working shader without GPU instancing;
Shader "VUE/Voxel Standard" {
Properties {
_Color ("Color", Color) = (1,1,1,1)
_MainTex ("Albedo (RGB)", 2D) = "white" {}
_Glossiness ("Smoothness", Range(0,1)) = 0.5
_Metallic ("Metallic", Range(0,1)) = 0.0
_ZOffset ("Z Buffer Offset", Float) = 0
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 200
Offset [_ZOffset], [_ZOffset]
CGPROGRAM
// Physically based Standard lighting model, and enable shadows on all light types
#pragma surface surf Standard fullforwardshadows
// Use shader model 3.0 target, to get nicer looking lighting
#pragma target 3.0
sampler2D _MainTex;
struct Input {
float4 color: COLOR;
float2 uv_MainTex;
};
half _Glossiness;
half _Metallic;
fixed4 _Color;
// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
// #pragma instancing_options assumeuniformscaling
UNITY_INSTANCING_BUFFER_START(Props)
// put more per-instance properties here
UNITY_INSTANCING_BUFFER_END(Props)
void surf (Input IN, inout SurfaceOutputStandard o) {
// Albedo comes from a texture tinted by color
fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
o.Albedo = c.rgb * IN.color; // Combine normal color with the vertex color
// Metallic and smoothness come from slider variables
o.Metallic = _Metallic;
o.Smoothness = _Glossiness;
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}