GPU Instancing + LOD Crossfade Error

I recently noticed that instancing seems to break the LOD Crossfading when switching Lods. The shader is just the standard one, with the crossfade pragma activated. When not setting the checkbox for instancing on the material, everything works fine.

As soon as gpu instancing is on, there appears to be a weird pop effect, which shouldn't be there. Has somebody an idea on how to get rid of this error?

In the first half gpu instancing is off, while in the second half it's on:

 

Nobody knows a solution for this? Maybe i should post a bug report then.

 

Hi, there shouldn't be a problem using gpu instancing with lod crossfade. I recently modified my shader to enable lod crossfade and I noticed similar pop effect like yours, but I then noticed that I put the UNITY_SETUP_INSTANCE_ID(IN); after UNITY_APPLY_DITHER_CROSSFADE(IN.vpos);
So you should probably check if your shader code looks like this:

UNITY_SETUP_INSTANCE_ID(IN);

UNITY_APPLY_DITHER_CROSSFADE(IN.vpos);

 

@Philip_Zhang Thanks for the tip! Gonna try it out, when i work on the shader again!

 

Hi,

I edited .cginc as recommended in the previous post, but I still have some problem with the shadows, can someone help me?

This is UnityStandardShadow.cginc:

Code (CSharp):

1. // Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)
2.  
3. #ifndef UNITY_STANDARD_SHADOW_INCLUDED
4. #define UNITY_STANDARD_SHADOW_INCLUDED
5.  
6. // NOTE: had to split shadow functions into separate file,
7. // otherwise compiler gives trouble with LIGHTING_COORDS macro (in UnityStandardCore.cginc)
8.  
9.  
10. #include "UnityCG.cginc"
11. #include "UnityShaderVariables.cginc"
12. #include "UnityStandardConfig.cginc"
13. #include "UnityStandardUtils.cginc"
14.  
15. #if (defined(_ALPHABLEND_ON) || defined(_ALPHAPREMULTIPLY_ON)) && defined(UNITY_USE_DITHER_MASK_FOR_ALPHABLENDED_SHADOWS)
16.     #define UNITY_STANDARD_USE_DITHER_MASK 1
17. #endif
18.  
19. // Need to output UVs in shadow caster, since we need to sample texture and do clip/dithering based on it
20. #if defined(_ALPHATEST_ON) || defined(_ALPHABLEND_ON) || defined(_ALPHAPREMULTIPLY_ON)
21. #define UNITY_STANDARD_USE_SHADOW_UVS 1
22. #endif
23.  
24. // Has a non-empty shadow caster output struct (it's an error to have empty structs on some platforms...)
25. #if !defined(V2F_SHADOW_CASTER_NOPOS_IS_EMPTY) || defined(UNITY_STANDARD_USE_SHADOW_UVS)
26. #define UNITY_STANDARD_USE_SHADOW_OUTPUT_STRUCT 1
27. #endif
28.  
29. #ifdef UNITY_STEREO_INSTANCING_ENABLED
30. #define UNITY_STANDARD_USE_STEREO_SHADOW_OUTPUT_STRUCT 1
31. #endif
32.  
33.  
34. half4       _Color;
35. half        _Cutoff;
36. sampler2D   _MainTex;
37. float4      _MainTex_ST;
38. #ifdef UNITY_STANDARD_USE_DITHER_MASK
39. sampler3D   _DitherMaskLOD;
40. #endif
41.  
42. // Handle PremultipliedAlpha from Fade or Transparent shading mode
43. half4       _SpecColor;
44. half        _Metallic;
45. #ifdef _SPECGLOSSMAP
46. sampler2D   _SpecGlossMap;
47. #endif
48. #ifdef _METALLICGLOSSMAP
49. sampler2D   _MetallicGlossMap;
50. #endif
51.  
52. #if defined(UNITY_STANDARD_USE_SHADOW_UVS) && defined(_PARALLAXMAP)
53. sampler2D   _ParallaxMap;
54. half        _Parallax;
55. #endif
56.  
57. half MetallicSetup_ShadowGetOneMinusReflectivity(half2 uv)
58. {
59.     half metallicity = _Metallic;
60.     #ifdef _METALLICGLOSSMAP
61.         metallicity = tex2D(_MetallicGlossMap, uv).r;
62.     #endif
63.     return OneMinusReflectivityFromMetallic(metallicity);
64. }
65.  
66. half RoughnessSetup_ShadowGetOneMinusReflectivity(half2 uv)
67. {
68.     half metallicity = _Metallic;
69. #ifdef _METALLICGLOSSMAP
70.     metallicity = tex2D(_MetallicGlossMap, uv).r;
71. #endif
72.     return OneMinusReflectivityFromMetallic(metallicity);
73. }
74.  
75. half SpecularSetup_ShadowGetOneMinusReflectivity(half2 uv)
76. {
77.     half3 specColor = _SpecColor.rgb;
78.     #ifdef _SPECGLOSSMAP
79.         specColor = tex2D(_SpecGlossMap, uv).rgb;
80.     #endif
81.     return (1 - SpecularStrength(specColor));
82. }
83.  
84. // SHADOW_ONEMINUSREFLECTIVITY(): workaround to get one minus reflectivity based on UNITY_SETUP_BRDF_INPUT
85. #define SHADOW_JOIN2(a, b) a##b
86. #define SHADOW_JOIN(a, b) SHADOW_JOIN2(a,b)
87. #define SHADOW_ONEMINUSREFLECTIVITY SHADOW_JOIN(UNITY_SETUP_BRDF_INPUT, _ShadowGetOneMinusReflectivity)
88.  
89. struct VertexInput
90. {
91.     float4 vertex   : POSITION;
92.     float3 normal   : NORMAL;
93.     float2 uv0      : TEXCOORD0;
94.     #if defined(UNITY_STANDARD_USE_SHADOW_UVS) && defined(_PARALLAXMAP)
95.         half4 tangent   : TANGENT;
96.     #endif
97.     UNITY_VERTEX_INPUT_INSTANCE_ID
98. };
99.  
100. #ifdef UNITY_STANDARD_USE_SHADOW_OUTPUT_STRUCT
101. struct VertexOutputShadowCaster
102. {
103.     V2F_SHADOW_CASTER_NOPOS
104.     #if defined(UNITY_STANDARD_USE_SHADOW_UVS)
105.         float2 tex : TEXCOORD1;
106.  
107.         #if defined(_PARALLAXMAP)
108.             half3 viewDirForParallax : TEXCOORD2;
109.         #endif
110.     #endif
111. };
112. #endif
113.  
114. #ifdef UNITY_STANDARD_USE_STEREO_SHADOW_OUTPUT_STRUCT
115. struct VertexOutputStereoShadowCaster
116. {
117.     UNITY_VERTEX_OUTPUT_STEREO
118. };
119. #endif
120.  
121. // We have to do these dances of outputting SV_POSITION separately from the vertex shader,
122. // and inputting VPOS in the pixel shader, since they both map to "POSITION" semantic on
123. // some platforms, and then things don't go well.
124.  
125.  
126. void vertShadowCaster (VertexInput v
127.     , out float4 opos : SV_POSITION
128.     #ifdef UNITY_STANDARD_USE_SHADOW_OUTPUT_STRUCT
129.     , out VertexOutputShadowCaster o
130.     #endif
131.     #ifdef UNITY_STANDARD_USE_STEREO_SHADOW_OUTPUT_STRUCT
132.     , out VertexOutputStereoShadowCaster os
133.     #endif
134. )
135. {
136.     UNITY_SETUP_INSTANCE_ID(v);
137.     #ifdef UNITY_STANDARD_USE_STEREO_SHADOW_OUTPUT_STRUCT
138.         UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(os);
139.     #endif
140.     TRANSFER_SHADOW_CASTER_NOPOS(o,opos)
141.     #if defined(UNITY_STANDARD_USE_SHADOW_UVS)
142.         o.tex = TRANSFORM_TEX(v.uv0, _MainTex);
143.  
144.         #ifdef _PARALLAXMAP
145.             TANGENT_SPACE_ROTATION;
146.             o.viewDirForParallax = mul (rotation, ObjSpaceViewDir(v.vertex));
147.         #endif
148.     #endif
149. }
150.  
151. half4 fragShadowCaster (UNITY_POSITION(vpos)
152. #ifdef UNITY_STANDARD_USE_SHADOW_OUTPUT_STRUCT
153.     , VertexOutputShadowCaster i
154. #endif
155. ) : SV_Target
156. {
157.     #if defined(UNITY_STANDARD_USE_SHADOW_UVS)
158.         #if defined(_PARALLAXMAP) && (SHADER_TARGET >= 30)
159.             half3 viewDirForParallax = normalize(i.viewDirForParallax);
160.             fixed h = tex2D (_ParallaxMap, i.tex.xy).g;
161.             half2 offset = ParallaxOffset1Step (h, _Parallax, viewDirForParallax);
162.             i.tex.xy += offset;
163.         #endif
164.  
165.         #if defined(_SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A)
166.             half alpha = _Color.a;
167.         #else
168.             half alpha = tex2D(_MainTex, i.tex.xy).a * _Color.a;
169.         #endif
170.         #if defined(_ALPHATEST_ON)
171.             clip (alpha - _Cutoff);
172.         #endif
173.         #if defined(_ALPHABLEND_ON) || defined(_ALPHAPREMULTIPLY_ON)
174.             #if defined(_ALPHAPREMULTIPLY_ON)
175.                 half outModifiedAlpha;
176.                 PreMultiplyAlpha(half3(0, 0, 0), alpha, SHADOW_ONEMINUSREFLECTIVITY(i.tex), outModifiedAlpha);
177.                 alpha = outModifiedAlpha;
178.             #endif
179.             #if defined(UNITY_STANDARD_USE_DITHER_MASK)
180.                 // Use dither mask for alpha blended shadows, based on pixel position xy
181.                 // and alpha level. Our dither texture is 4x4x16.
182.                 #ifdef LOD_FADE_CROSSFADE
183.                     #define _LOD_FADE_ON_ALPHA
184.                     alpha *= unity_LODFade.y;
185.                 #endif
186.                 half alphaRef = tex3D(_DitherMaskLOD, float3(vpos.xy*0.25,alpha*0.9375)).a;
187.                 clip (alphaRef - 0.01);
188.             #else
189.                 clip (alpha - _Cutoff);
190.             #endif
191.         #endif
192.     #endif // #if defined(UNITY_STANDARD_USE_SHADOW_UVS)
193.  
194.     #ifdef LOD_FADE_CROSSFADE
195.         #ifdef _LOD_FADE_ON_ALPHA
196.             #undef _LOD_FADE_ON_ALPHA
197.         #else
198.             UnityApplyDitherCrossFade(vpos.xy);
199.         #endif
200.     #endif
201.  
202.     SHADOW_CASTER_FRAGMENT(i)
203. }
204.  
205. #endif // UNITY_STANDARD_SHADOW_INCLUDED
206.  

 

I solved with the help of this site:
https://catlikecoding.com/unity/tutorials/rendering/part-19/
however I had to modify the .cginc and it is not a pleasant thing .. it would be the case that unity provided this functionality by default.

 

Monil, could you please provide any details on how you fixed this? I can get LOD cross fading to work ok except when using GPU instanced - same problem that flogel illustrated. I checked the catlike tutorials but cannot figure what modifications are required in .cginc files.'

Edit:
Ok I got the fade working well with instanced. However I am stuck at the shadows like you were. Hoping you can enlighten me on changes you made to UnityStandardShadow.cginc. Thanks.

 

You have to pass the instanceID from the vertex to the fragment shader, and then call UNITY_SETUP_INSTANCE_ID(IN); in the frag shader, before calling any lod fade functions.

You need to do it for both your regular and shadow passes.

The standard shader doesn't do this as it doesn't support lods.