/// author：Saber
/// desc:角色相机泛光效果脚本
/// 2020年2月21日优化：参考了catlikecoding的模糊思路优化逻辑提升效果，模糊rt使用局部摄像机获取到的画面进行处理
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
[ExecuteInEditMode]
[RequireComponent(typeof(Camera))]
public class RoleCameraBloom : MonoBehaviour
{
    public RenderTexture cullRenderTexture; // 用来接收泛光相机的裁剪RT
    private ChangeShaderRender scr_script; // 泛光摄像机上的渲染脚本
    #region 泛光特效相关参数
    //模糊散值
    public Material bloomMaterial; // 泛光特效相关材质
    public bool render_bloom_effect = false;   // 泛光特效关键参数，设置为true时会开始渲染泛光特效

    #endregion
    private bool isSupported; // 设备支持变量
    // 模糊摄像机获取到的画面依然需要做阈值处理，不过初始默认值为0
    [Range(0, 10)]
	public float threshold = 1;
    // 避免阈值附近的画面忽然点亮，这里设置一个软阈值处理阈值附近的颜色值的泛光效果
	[Range(0, 1)]
	public float softThreshold = 0.5f;
    [Range(0, 10)]
	public float intensity = 1;
    #region 渲染pass常量
    const int BoxDownPrefilterPass = 0; // 对泛光部分降采样的pass
	const int BoxDownPass = 1; // 降序采样pass
	const int BoxUpPass = 2; // 升序采样pass，最大限度利用到所有的像素颜色贡献
	const int ApplyBloomPass = 3; // 泛光颜色叠加pass
	const int DebugBloomPass = 4; // 测试pass，不叠加原颜色，只渲染泛光处理的效果
    #endregion
    [Range(1, 8)]
	public int iterations = 4; // 泛光迭代次数
    RenderTexture[] textures = new RenderTexture[8]; // 临时纹理链表
    RenderTexture currentDestination; 
    RenderTexture currentSource;
    Vector4 filter; // 膝盖曲线过滤值
    public bool debug = false;
    // Start is called before the first frame update
    void Start()
    {
        // 检查平台支持，不支持则直接禁用
        isSupported = CheckSupport();
        this.enabled = isSupported;
        if(scr_script != null){
            scr_script.enabled = isSupported;
        }
        // 测试逻辑
        // TestLogic();
    }
    #region 测试逻辑
        private void TestLogic()
        {
            RenderTexture temp_render = new RenderTexture(1280, 600, 0);
            GameObject child = this.transform.GetChild(0).gameObject;
            Camera temp_camera = child.GetComponent<Camera>();
            child.AddComponent<ChangeShaderRender>();
            ChangeShaderRender temp_scr = child.GetComponent<ChangeShaderRender>();
            Shader shader = Shader.Find("SaberShader/BloomClipShader");
            temp_scr.target_shader = shader;
            SetBloomCameraData(temp_camera, temp_render, temp_scr);
        }
    #endregion
    private bool CheckSupport()
    {
        if (SystemInfo.supportsImageEffects == false)
        {
            Debug.LogWarning("当前平台不支持！");
            return false;
        }
        return true;
    }
    // Lua接口，将泛光摄像机和泛光摄像机输出的rt交给本类来控制
    public void SetBloomCameraData(Camera camera, RenderTexture rt, ChangeShaderRender change_shader_render){
        cullRenderTexture = rt;
        camera.targetTexture = cullRenderTexture;
        render_bloom_effect = true;
        scr_script = change_shader_render;
        // 效果运行与否还要看设备支不支持特效
        scr_script.enabled = isSupported;
    }
    // 正式渲染
    // 这个方法要注意在退出游戏的时候把渲染逻辑门关闭，一般情况下把render_bloom_effect置false
    void OnRenderImage(RenderTexture src, RenderTexture dest)
    {
        if (bloomMaterial != null && render_bloom_effect && cullRenderTexture != null)
        {
            // 膝盖曲线的值可以在这里预先算好
            float knee = threshold * softThreshold;
            filter.x = threshold;
            filter.y = filter.x - knee;
            filter.z = 2f * knee;
            filter.w = 0.25f / (knee + 0.00001f);
            bloomMaterial.SetVector("_Filter", filter);
            bloomMaterial.SetFloat("_Intensity", Mathf.GammaToLinearSpace(intensity));
            // 降低一次采样，将剧目摄像机的内容传递到临时的最终画面RT中
            int width = src.width / 4;
            int height = src.height / 4;
            currentDestination = textures[0] = RenderTexture.GetTemporary(width, height, 0, src.format);
            Graphics.Blit(cullRenderTexture, currentDestination, bloomMaterial, BoxDownPrefilterPass);
            currentSource = currentDestination;

            // 循环降采样，并将结果保存
            int i = 1;
            for (; i < iterations; i++) {
                width /= 2;
                height /= 2;
                if (height < 2) {
                    break;
                }
                currentDestination = textures[i] =
                    RenderTexture.GetTemporary(width, height, 0, src.format);
                Graphics.Blit(currentSource, currentDestination, bloomMaterial, BoxDownPass);
                currentSource = currentDestination;
            }
            // 再对降采样后的画面继续宁升采样，将每个像素的颜色平均出去
            for (i -= 2; i >= 0; i--) {
                currentDestination = textures[i];
                textures[i] = null;
                Graphics.Blit(currentSource, currentDestination, bloomMaterial, BoxUpPass);
                RenderTexture.ReleaseTemporary(currentSource);
                currentSource = currentDestination;
            }

            if (debug) {
                Graphics.Blit(currentSource, dest, bloomMaterial, DebugBloomPass);
            }
            else {
                bloomMaterial.SetTexture("_SourceTex", src);
                Graphics.Blit(currentSource, dest, bloomMaterial, ApplyBloomPass);
            }
            RenderTexture.ReleaseTemporary(currentSource);
        }
        else
        {
            Graphics.Blit(src, dest);
        }
    }
    public void ReleaseTempRes()
    {
        render_bloom_effect = false;
        if(scr_script != null)
        {
            scr_script.enabled = false;
        }
    }
    void OnDestroy(){
        ReleaseTempRes();
    }
}