Trying to access time in an HLSL post-processing shader. Am I doing anything wrong?

[cs5947]

Here’s the code:

Shader “Hidden/Shader/DitherGrain”
{
Properties
{
// This property is necessary to make the CommandBuffer.Blit bind the source texture to _MainTex
_MainTex(“Main Texture”, 2DArray) = “grey” {}
}
HLSLINCLUDE
#pragma target 4.5
#pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch
#include “Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl”
#include “Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl”
#include “Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl”
#include “Packages/com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/FXAA.hlsl”
#include “Packages/com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/RTUpscale.hlsl”
struct Attributes
{
uint vertexID : SV_VertexID;
UNITY_VERTEX_INPUT_INSTANCE_ID
};
struct Varyings
{
float4 positionCS : SV_POSITION;
float2 texcoord : TEXCOORD0;
UNITY_VERTEX_OUTPUT_STEREO
};
Varyings Vert(Attributes input)
{
Varyings output;
UNITY_SETUP_INSTANCE_ID(input);
UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);
output.positionCS = GetFullScreenTriangleVertexPosition(input.vertexID);
output.texcoord = GetFullScreenTriangleTexCoord(input.vertexID);
return output;
}
// List of properties to control your post process effect
float _Intensity;
float time = _Time.x;
TEXTURE2D_X(_MainTex);
float4 CustomPostProcess(Varyings input) : SV_Target
{
UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
// Note that if HDUtils.DrawFullScreen is not used to render the post process, you don’t need to call ClampAndScaleUVForBilinearPostProcessTexture.
float3 sourceColor = SAMPLE_TEXTURE2D_X(_MainTex, s_linear_clamp_sampler, ClampAndScaleUVForBilinearPostProcessTexture(input.texcoord.xy)).xyz;
// Hash function, algorithm directly copied from Dave_Hoskins on Shadertoy. Credits to him.
float Hash(float2 p)
{
return frac(sin(dot(p, float2(12.9898, 78.233))) * 43758.5453);
}
// Apply greyscale effect
float3 color = lerp(sourceColor, Hash(input.texcoord.xy + time), _Intensity);
return float4(color, 1);
}
ENDHLSL
SubShader
{
Tags{ “RenderPipeline” = “HDRenderPipeline” }
Pass
{
Name “DitherGrain”
ZWrite Off
ZTest Always
Blend Off
Cull Off
HLSLPROGRAM
#pragma fragment CustomPostProcess
#pragma vertex Vert
ENDHLSL
}
}
Fallback Off
}

I’m getting this error:

Shader error in ‘Hidden/Shader/DitherGrain’: ‘time’: initial value must be a literal expression at line 46 (on d3d11)
Compiling Subshader: 0, Pass: DitherGrain, Fragment program with
Platform defines: SHADER_API_DESKTOP UNITY_ENABLE_DETAIL_NORMALMAP UNITY_ENABLE_REFLECTION_BUFFERS UNITY_LIGHTMAP_FULL_HDR UNITY_LIGHT_PROBE_PROXY_VOLUME UNITY_PBS_USE_BRDF1 UNITY_SPECCUBE_BLENDING UNITY_SPECCUBE_BOX_PROJECTION UNITY_USE_DITHER_MASK_FOR_ALPHABLENDED_SHADOWS
Disabled keywords: SHADER_API_GLES30 UNITY_ASTC_NORMALMAP_ENCODING UNITY_COLORSPACE_GAMMA UNITY_FRAMEBUFFER_FETCH_AVAILABLE UNITY_HARDWARE_TIER1 UNITY_HARDWARE_TIER2 UNITY_HARDWARE_TIER3 UNITY_LIGHTMAP_DLDR_ENCODING UNITY_LIGHTMAP_RGBM_ENCODING UNITY_METAL_SHADOWS_USE_POINT_FILTERING UNITY_NO_DXT5nm UNITY_NO_SCREENSPACE_SHADOWS UNITY_PBS_USE_BRDF2 UNITY_PBS_USE_BRDF3 UNITY_PRETRANSFORM_TO_DISPLAY_ORIENTATION UNITY_UNIFIED_SHADER_PRECISION_MODEL UNITY_VIRTUAL_TEXTURING

If you need any extra information you can use to help, I’m working Unity 2023.2.0 with an HDRP project. What I’m trying to do is to create a simple static effect that creates a psuedo-random value for each pixel, and refreshes the pixels based on time each frame. I’m new to HLSL but I dont think this should be way too hard of a shader to make. I’m using this shader from Shadertoy to copy into HLSL so I at least have an understanding of how the values are generated and refreshed.

[cs5947]

I am aware that there may be errors aside from this one inside of the code, you’re welcome to fix them and tell me how you fixed them so that I may know later. Thanks, cs5947

[StaggartCreations]

Unlike in C#, you can’t declare properties with an initial value, linking to yet another property. The error hints at this, but it’s really asking you to make the value a constant.

You can:

• Declare it as a local property in the CustomPostProcess function
• Change it to a macro (#define time _Time.x) (no semicolumn at the end!)
• Replace the usage of the ‘time’ variable with ‘_Time.x’.

Have you noticed the “Hash” function is also nested in the CustomPostProcess function? That needs to be moved up outside of the function’s scope.

Side note: best to replace ‘_Time’ with ‘_TimeParameters’. The former is legacy code, whilst the latter is the SRP standard.