CloudsExporter.cs

using System;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.PostProcessing;

[Serializable]
[PostProcess(typeof(CloudsExporterRenderer), PostProcessEvent.AfterStack, "Custom/CloudsExporter")]
public sealed class CloudsExporter : PostProcessEffectSettings
{
    public FloatParameter MinHeight = new FloatParameter { value = 0.0f };
    public FloatParameter MaxHeight = new FloatParameter { value = 5.0f };
    public FloatParameter FadeDist = new FloatParameter { value = 2f };
    public FloatParameter Scale = new FloatParameter { value = 5f };

    public TextureParameter ValueNoiseTable = new TextureParameter { value = null };
}

public sealed class CloudsExporterRenderer: PostProcessEffectRenderer<CloudsExporter>
{
    public override void Render(PostProcessRenderContext context)
    {
        Transform Sun = GameObject.FindGameObjectWithTag("MainLight").transform;
        Camera _Cam = Camera.main;

        var shader = context.propertySheets.Get(Shader.Find("Raymarch/clouds2"));
        //sheet.properties.SetFloat("_Blend", settings.blend);

        if (_Cam == null)
            _Cam = Camera.main;

        shader.properties.SetTexture("_ValueNoise", settings.ValueNoiseTable);

        if (Sun != null)
        {
            RenderSettings.skybox.SetVector("_SunDir", -Sun.forward);
            shader.properties.SetVector("_SunDir", -Sun.forward);
        }
        else
        {
            RenderSettings.skybox.SetVector("_SunDir", Vector3.up);
            shader.properties.SetVector("_SunDir", Vector3.up);
        }

        shader.properties.SetFloat("_MinHeight", settings.MinHeight);
        shader.properties.SetFloat("_MaxHeight", settings.MaxHeight);
        shader.properties.SetFloat("_FadeDist", settings.FadeDist);
        shader.properties.SetFloat("_Scale", settings.Scale);

        shader.properties.SetMatrix("_FrustumCornersWS", GetFrustumCorners(_Cam));
        shader.properties.SetMatrix("_CameraInvViewMatrix", _Cam.cameraToWorldMatrix);
        shader.properties.SetVector("_CameraWS", _Cam.transform.position);
        
        CustomGraphicsBlit(context.source, context.destination, shader.properties, 0);
        context.command.BlitFullscreenTriangle(context.source, context.destination, shader, 0);
    }

    private Matrix4x4 GetFrustumCorners(Camera cam)
    {
        float camFov = cam.fieldOfView;
        float camAspect = cam.aspect;

        Matrix4x4 frustumCorners = Matrix4x4.identity;

        float fovWHalf = camFov * 0.5f;

        float tan_fov = Mathf.Tan(fovWHalf * Mathf.Deg2Rad);

        Vector3 toRight = Vector3.right * tan_fov * camAspect;
        Vector3 toTop = Vector3.up * tan_fov;

        Vector3 topLeft = (-Vector3.forward - toRight + toTop);
        Vector3 topRight = (-Vector3.forward + toRight + toTop);
        Vector3 bottomRight = (-Vector3.forward + toRight - toTop);
        Vector3 bottomLeft = (-Vector3.forward - toRight - toTop);

        frustumCorners.SetRow(0, topLeft);
        frustumCorners.SetRow(1, topRight);
        frustumCorners.SetRow(2, bottomRight);
        frustumCorners.SetRow(3, bottomLeft);

        return frustumCorners;
    }

    static void CustomGraphicsBlit(RenderTargetIdentifier source, RenderTargetIdentifier dest, MaterialPropertyBlock fxMaterial, int passNr)
    {
        //RenderTexture.active = dest.tex;

        //fxMaterial.SetTexture("_MainTex", source);

        GL.PushMatrix();
        GL.LoadOrtho();

        //fxMaterial.SetPass(passNr);

        GL.Begin(GL.QUADS);

        GL.MultiTexCoord2(0, 0.0f, 0.0f);
        GL.Vertex3(0.0f, 0.0f, 3.0f); // BL

        GL.MultiTexCoord2(0, 1.0f, 0.0f);
        GL.Vertex3(1.0f, 0.0f, 2.0f); // BR

        GL.MultiTexCoord2(0, 1.0f, 1.0f);
        GL.Vertex3(1.0f, 1.0f, 1.0f); // TR

        GL.MultiTexCoord2(0, 0.0f, 1.0f);
        GL.Vertex3(0.0f, 1.0f, 0.0f); // TL

        GL.End();
        GL.PopMatrix();
    }
}

[Serializable]
public sealed class TransformParameter : ParameterOverride<Transform> { }

[Serializable]
public sealed class ShaderParameter : ParameterOverride<Shader> { }