Unity Texture Texture2D RenderTexture

http://fargesportfolio.com/unity-texture-texture2d-rendertexture/

(1) Texture 基于GPU

(2) RenderTexture基于GPU

(3)Texture2D基于CPU      Texture2D.Apply将CPU数据传递给GPU

/// Pass a GPU RenderTexture to CPU Texture2D
/// This opperation has heavy cost (ReadPixels)
/// We reduice the RenderTexture size first to be more efficient
 
void RenderTextureToTexture2D()
{
 
	// Please, be power of 2 for performance issue (2, 4, 8, ...)
	int downSize = 2;
 
	RenderTexture textureToDownsizeAndCopyToCPU = new RenderTexture(1920, 1080, 0);
	Texture2D newTexture2DToBeLoadedTo = new Texture2D(textureToDownsizeAndCopyToCPU.width / downSize, textureToDownsizeAndCopyToCPU.height / downSize, TextureFormat.ARGB32, false);
 
	// Load textureToDownsizeAndCopyToCPU from something you like...
 
	// Create a temporary downsized texture
	RenderTexture textureDownsized = RenderTexture.GetTemporary(textureToDownsizeAndCopyToCPU.width / downSize, textureToDownsizeAndCopyToCPU.height / downSize);
 
	// Remember currently active render texture
	RenderTexture currentActiveRT = RenderTexture.active;
 
	RenderTexture.active = textureDownsized;
 
	// Copy textureToDownsizeAndCopyToCPU to textureDownsized
	Graphics.Blit(textureToDownsizeAndCopyToCPU, textureDownsized);
 
	// Read the RenderTexture image into it
	// Pass GPU bytes to CPU
        // Very performance consuming
	newTexture2DToBeLoadedTo.ReadPixels(new Rect(0, 0, textureDownsized.width, textureDownsized.height), 0, 0, false);
	// Debug.Log(tex2D.width + " " + tex2D.height);
	// Restorie previously active render texture
	RenderTexture.active = currentActiveRT;
 
	RenderTexture.ReleaseTemporary(textureDownsized);
}
 
 
void RenderTextureFromShader()
{
        Graphics.Blit(null, RenderTextureDestination, materialShader);
}

 

1: 赋值图片是灰色

Graphics.CopyTexture（或Graphics.Blit）在GPU端工作，而ReadPixels在CPU上工作。这就是为什么CPU上的EncodetoJPG在ReadPixels而不是CopyTexture之后工作的原因。

您必须使用此程序将JPG保存到磁盘

https://answers.unity.com/questions/1479723/encodetojpg-creates-gray-image-after-using-copytex.html

2:将RenderTexture转换为Texture2D

RenderTexture.active = myRenderTexture;
myTexture2D.ReadPixels(new Rect(0, 0, myRenderTexture.width, myRenderTexture.height), 0, 0);
myTexture2D.Apply();

3:Texture2D到RenderTexture

 // texRef is your Texture2D
 // You can also reduice your texture 2D that way
    RenderTexture rt = new RenderTexture(texRef.width / 2, texRef.height / 2, 0);
    RenderTexture.active = rt;
    // Copy your texture ref to the render texture
    Graphics.Blit(texRef, rt);
         
    // Now you can read it back to a Texture2D if you care
    if (tex2D == null)
         tex2D = new Texture2D(rt.width, rt.height, TextureFormat.RGBA32, true);
    tex2D.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0, false);