Here’s my setup:
I have some grass, and some trees. It sways with the wind by animating vertex positions.
I’m about to start generating a bunch of grass, and would like to get instancing working. The shader works perfectly fine without instancing.
When I turn it on, I have two issues:
-
I can see the shadows of object behind the grass sometimes.
-
When in front of my water, which reads from depth texture to determine color and foam, I can see that animated vertex positions for my grass differ between the depth texture write and the rest of the shader.
If I go into the frame debugger, I can clearly see that the grass animates the exact same way for all my meshes, during the depth pass. But in the actual drawing of the object, the animation is correct.
I guess the GPU instancing breaks the per instance world matrixes for the depth pass, resulting in different outputs.
I’ve been at this for some hours now and can’t find a solution. Anybody out there with some ideas?
Here’s the shader code. Note that the lighting function and wind function are in cgincludes. The wind function is in the bottom.
SubShader
{
Pass
{
AlphaToMask On
Cull[_Cull]
Tags
{
"RenderType"="TransparentCutout"
"LightMode"="ForwardBase"
"IgnoreProjector"="True"
"Queue"="AlphaTest"
}
CGPROGRAM
#include "Assets/Shaders/Fog/Fog.cginc"
#include "Assets/Shaders/Toon/ToonVegetation.cginc"
#include "Assets/Shaders/Wind.cginc"
#include "AutoLight.cginc"
#include "UnityCG.cginc"
#pragma vertex vert
#pragma fragment frag
#pragma shader_feature FOG_NOISE
#pragma shader_feature SSS
#pragma shader_feature RIM
#pragma shader_feature_local WIND
#pragma shader_feature_local WIND_UV
#pragma multi_compile_fwdbase
#pragma multi_compile_instancing
sampler2D _MainTex;
float4 _MainTex_ST;
fixed _Cutoff;
struct appdata
{
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 uv : TEXCOORD0;
UNITY_VERTEX_INPUT_INSTANCE_ID
};
struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
float3 worldPos : TEXCOORD1;
float3 viewDir : TEXCOORD2;
SHADOW_COORDS(3)
float3 normal : NORMAL;
float4 color : COLOR;
UNITY_VERTEX_INPUT_INSTANCE_ID
};
inline float3 positionToNormal(float3 position)
{
float3 dpx = ddx( position );
float3 dpy = ddy( position ) * _ProjectionParams.x;
return normalize(cross(dpx, dpy));
}
float _WindScale;
v2f vert (appdata v)
{
v2f o;
UNITY_SETUP_INSTANCE_ID(v);
UNITY_TRANSFER_INSTANCE_ID(v, o);
float4 vert = v.vertex;
#if WIND
#if WIND_UV
vert = WindPosition(vert, _WindScale * step(0.1, v.uv.y));
#else
vert = WindPosition(vert, _WindScale);
#endif
#endif
o.pos = UnityObjectToClipPos(vert);
o.worldPos = mul(unity_ObjectToWorld, vert);
o.normal = mul(unity_ObjectToWorld, v.normal);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
o.color = lerp(UNITY_ACCESS_INSTANCED_PROP(Props, _BottomColor), UNITY_ACCESS_INSTANCED_PROP(Props, _TopColor), saturate(vert.y));
o.viewDir = WorldSpaceViewDir(vert);
TRANSFER_SHADOW(o);
return o;
}
half4 frag(v2f i) : SV_Target
{
UNITY_SETUP_INSTANCE_ID(i);
half4 col = i.color * tex2D(_MainTex, i.uv);
float3 origNormal = positionToNormal(i.worldPos);
float viewFactor = abs(dot(origNormal, -normalize(i.viewDir)));
col.a = (col.a - _Cutoff) / max(fwidth(col.a), 0.0001) + 0.5;
col.a *= viewFactor;
col = LightingToonVegetation(col, i.normal, _WorldSpaceLightPos0.xyz, i.viewDir, SHADOW_ATTENUATION(i));
col = ApplyFogAlphaBlend(i.worldPos, i.pos.w, col);
return col;
}
ENDCG
}
Pass
{
Cull[_Cull]
AlphaToMask On
Tags { "LightMode" = "ShadowCaster"}
CGPROGRAM
#include "Assets/Shaders/Wind.cginc"
#include "UnityCG.cginc"
#pragma shader_feature_local WIND
#pragma shader_feature_local WIND_UV
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_shadowcaster
#pragma multi_compile_instancing
float _Cutoff;
sampler2D _MainTex;
float4 _MainTex_ST;
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
UNITY_VERTEX_INPUT_INSTANCE_ID
};
struct v2f
{
V2F_SHADOW_CASTER;
UNITY_VERTEX_INPUT_INSTANCE_ID
float3 worldPos : TEXCOORD2;
float2 uv : TEXCOORD1;
float3 viewDir : TEXCOORD03;
};
inline float3 positionToNormal(float3 position)
{
float3 dpx = ddx( position );
float3 dpy = ddy( position ) * _ProjectionParams.x;
return normalize(cross(dpx, dpy));
}
float _WindScale;
v2f vert(appdata v)
{
v2f o;
UNITY_SETUP_INSTANCE_ID(v);
UNITY_TRANSFER_INSTANCE_ID(v, o);
float4 vert = v.vertex;
#if WIND
#if WIND_UV
vert = WindPosition(vert, _WindScale * step(0.1, v.uv.y));
#else
vert = WindPosition(vert, _WindScale);
#endif
#endif
o.viewDir = WorldSpaceViewDir(v.vertex);
o.worldPos = mul(unity_ObjectToWorld, vert.xyz);
o.pos = UnityObjectToClipPos(vert);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
return o;
}
half4 frag(v2f i) : SV_Target
{
UNITY_SETUP_INSTANCE_ID(i);
half4 col = tex2D(_MainTex, i.uv);
float3 origNormal = positionToNormal(i.worldPos);
float viewFactor = abs(dot(origNormal, -normalize(i.viewDir)));
col.a = (col.a - _Cutoff) / max(fwidth(col.a), 0.0001) + 0.5;
col.a *= viewFactor;
return col;
}
ENDCG
}
}
Wind function:
inline float4 WindPosition(float4 vertex, half strength)
{
float3 worldPos = mul(unity_ObjectToWorld, float4(vertex.xyz, 1)).xyz;
float noise = tex2Dlod(_WindNoise, float4(( worldPos.xz * _WindFrequency - _WindDirection.xz * _WindSpeed * _Time.x) ,0,0));
float3 wind = noise * _WindDirection * strength * _WindStrength;
return float4(mul(unity_WorldToObject, float4(worldPos + wind, 1)).xyz, vertex.w);
}
