本文为大家分享了Unity实现粒子光效导出成png序列帧的具体代码,供大家参考,具体内容如下
这个功能并不是很实用,不过美术同学有这样的需求,那么就花了一点时间研究了下。
我们没有使用Unity的引擎,但是做特效的同学找了一批Unity的粒子特效,希望导出成png序列帧的形式,然后我们的游戏来使用。这个就相当于拿Unity做了特效编辑器的工作。这个并不是很“邪门”,因为用幻影粒子,或者3dmax,差不多也是这个思路,只不过那些软件提供了正规的导出功能,而Unity则没有。
先上代码
using UnityEngine; using UnityEditor; using System; using System.IO; using System.Collections; using System.Collections.Generic; public class ParticleExporter : MonoBehaviour { // Default folder name where you want the animations to be output public string folder = "PNG_Animations"; // Framerate at which you want to play the animation public int frameRate = 25; // export frame rate 导出帧率,设置Time.captureFramerate会忽略真实时间,直接使用此帧率 public float frameCount = 100; // export frame count 导出帧的数目,100帧则相当于导出5秒钟的光效时间。由于导出每一帧的时间很长,所以导出时间会远远长于直观的光效播放时间 public int screenWidth = 960; // not use 暂时没用,希望可以直接设置屏幕的大小(即光效画布的大小) public int screenHeight = 640; public Vector3 cameraPosition = Vector3.zero; public Vector3 cameraRotation = Vector3.zero; private string realFolder = ""; // real folder where the output files will be private float originaltimescaleTime; // track the original time scale so we can freeze the animation between frames private float currentTime = 0; private bool over = false; private int currentIndex = 0; private Camera exportCamera; // camera for export 导出光效的摄像机,使用RenderTexture public void Start() { // set frame rate Time.captureFramerate = frameRate; // Create a folder that doesn't exist yet. Append number if necessary. realFolder = Path.Combine(folder, name); // Create the folder if (!Directory.Exists(realFolder)) { Directory.CreateDirectory(realFolder); } originaltimescaleTime = Time.timeScale; GameObject goCamera = Camera.main.gameObject; if (cameraPosition != Vector3.zero) { goCamera.transform.position = cameraPosition; } if (cameraRotation != Vector3.zero) { goCamera.transform.rotation = Quaternion.Euler(cameraRotation); } GameObject go = Instantiate(goCamera) as GameObject; exportCamera = go.GetComponent<Camera>(); currentTime = 0; } void Update() { currentTime += Time.deltaTime; if (!over && currentIndex >= frameCount) { over = true; Cleanup(); Debug.Log("Finish"); return; } // 每帧截屏 StartCoroutine(CaptureFrame()); } void Cleanup() { DestroyImmediate(exportCamera); DestroyImmediate(gameObject); } IEnumerator CaptureFrame() { // Stop time Time.timeScale = 0; // Yield to next frame and then start the rendering // this is important, otherwise will have error yield return new WaitForEndOfFrame(); string filename = String.Format("{0}/{1:D04}.png", realFolder, ++currentIndex); Debug.Log(filename); int width = Screen.width; int height = Screen.height; //Initialize and render textures RenderTexture blackCamRenderTexture = new RenderTexture(width, height, 24, RenderTextureFormat.ARGB32); RenderTexture whiteCamRenderTexture = new RenderTexture(width, height, 24, RenderTextureFormat.ARGB32); exportCamera.targetTexture = blackCamRenderTexture; exportCamera.backgroundColor = Color.black; exportCamera.Render(); RenderTexture.active = blackCamRenderTexture; Texture2D texb = GetTex2D(); //Now do it for Alpha Camera exportCamera.targetTexture = whiteCamRenderTexture; exportCamera.backgroundColor = Color.white; exportCamera.Render(); RenderTexture.active = whiteCamRenderTexture; Texture2D texw = GetTex2D(); // If we have both textures then create final output texture if (texw && texb) { Texture2D outputtex = new Texture2D(width, height, TextureFormat.ARGB32, false); // we need to check alpha ourselves,because particle use additive shader // Create Alpha from the difference between black and white camera renders for (int y = 0; y < outputtex.height; ++y) { // each row for (int x = 0; x < outputtex.width; ++x) { // each column float alpha; alpha = texw.GetPixel(x, y).r - texb.GetPixel(x, y).r; alpha = 1.0f - alpha; Color color; if (alpha == 0) { color = Color.clear; } else { color = texb.GetPixel(x, y); } color.a = alpha; outputtex.SetPixel(x, y, color); } } // Encode the resulting output texture to a byte array then write to the file byte[] pngShot = outputtex.EncodeToPNG(); File.WriteAllBytes(filename, pngShot); // cleanup, otherwise will memory leak pngShot = null; RenderTexture.active = null; DestroyImmediate(outputtex); outputtex = null; DestroyImmediate(blackCamRenderTexture); blackCamRenderTexture = null; DestroyImmediate(whiteCamRenderTexture); whiteCamRenderTexture = null; DestroyImmediate(texb); texb = null; DestroyImmediate(texw); texb = null; System.GC.Collect(); // Reset the time scale, then move on to the next frame. Time.timeScale = originaltimescaleTime; } } // Get the texture from the screen, render all or only half of the camera private Texture2D GetTex2D() { // Create a texture the size of the screen, RGB24 format int width = Screen.width; int height = Screen.height; Texture2D tex = new Texture2D(width, height, TextureFormat.ARGB32, false); // Read screen contents into the texture tex.ReadPixels(new Rect(0, 0, width, height), 0, 0); tex.Apply(); return tex; } }
这里对几个关键的知识点来做说明:
1、整体思路是这样的,Unity中调整好摄像机,正常播放特效,然后每帧截屏,保存成我们需要的png序列帧。这个不仅仅是特效可以这么用,其实模型也可以。比如我们需要同屏显示几百上千人,或者是无关紧要的怪物、场景物件等等,就可以使用这个导出成2d的序列帧,可以大大提高效率,使一些不可能的情况变为可能。
2、关于时间和帧率的控制。由于截屏所需要的时间远远大于帧间隔,所以光效如果是播放1秒,则导出时间可能超过一分钟。Time.captureFrameRate可以设置帧率,设置后则忽略真实时间,光效、模型会按照帧率的时间来播放。这个接口恰好就是用在视频录制上的。
3、光效画布控制。这个暂时没有找到好的方法,由于是全屏幕截屏,所以Game窗口的大小就是光效画布的大小。
4、通过调整摄像机的位置、旋转,控制光效的显示信息。
5、截屏函数就是GetTex2D()。这里面最主要的是ReadPixels函数。需要注意,CaptureFrame函数必须要以协程的方式运行,因为里面有一句yield return new WaitForEndOfFrame();如果没有这一句,会报一个错误,大概意思就是ReadPixels不在DrawFrame里面运行。
6、截屏时间消耗很大,所以需要在截屏开始使用Time.timeScale=0暂停时间运行,截屏后再恢复
7、注意截屏操作完成后清理各种资源,并进行GC。否则内存很有可能就不够用了,截100帧图片,内存很有可能就两三G了。
8、截屏的时候使用了两个RenderTexture,分别绘制白底和黑底的图片,然后根据这两张图片计算出alpha。如果不是光效其实可以不这么麻烦,直接把Camera的backgroundColor中的alpha设置为0就可以了。但是光效使用了特殊的shader,比如Additive,这里涉及到alpha blend。绘制光效时如果也这样设置的话,导出的图片没有任何东西。所以必须要有实色背景。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持易盾网络。