UnityEngine.RenderTexture.DiscardContents C# (CSharp) Method

        public extern void DiscardContents(bool discardColor, bool discardDepth);
        /// <summary>

        // flat blur
        void Blur(RenderTexture from  ,RenderTexture  to , int iterations  , int blurPass, float spread  )
        {
            RenderTexture tmp  = RenderTexture.GetTemporary (to.width, to.height, 0);

            if (iterations < 2) {
                dofBlurMaterial.SetVector ("offsets", new Vector4 (0.0f, spread * oneOverBaseSize, 0.0f, 0.0f));
                tmp.DiscardContents ();
                Graphics.Blit (from, tmp, dofBlurMaterial, blurPass);

                dofBlurMaterial.SetVector ("offsets", new Vector4 (spread / widthOverHeight * oneOverBaseSize,  0.0f, 0.0f, 0.0f));
                to.DiscardContents ();
                Graphics.Blit (tmp, to, dofBlurMaterial, blurPass);
            }
            else {
                dofBlurMaterial.SetVector ("offsets", new Vector4 (0.0f, spread * oneOverBaseSize, 0.0f, 0.0f));
                tmp.DiscardContents ();
                Graphics.Blit (from, tmp, dofBlurMaterial, blurPass);

                dofBlurMaterial.SetVector ("offsets", new Vector4 (spread / widthOverHeight * oneOverBaseSize,  0.0f, 0.0f, 0.0f));
                to.DiscardContents ();
                Graphics.Blit (tmp, to, dofBlurMaterial, blurPass);

                dofBlurMaterial.SetVector ("offsets", new Vector4 (spread / widthOverHeight * oneOverBaseSize,  spread * oneOverBaseSize, 0.0f, 0.0f));
                tmp.DiscardContents ();
                Graphics.Blit (to, tmp, dofBlurMaterial, blurPass);

                dofBlurMaterial.SetVector ("offsets", new Vector4 (spread / widthOverHeight * oneOverBaseSize,  -spread * oneOverBaseSize, 0.0f, 0.0f));
                to.DiscardContents ();
                Graphics.Blit (tmp, to, dofBlurMaterial, blurPass);
            }

            RenderTexture.ReleaseTemporary (tmp);
        }