using System; using UnityEditor; using UnityEngine; public class NormalMapAverageLengthTexturePostprocessor : AssetPostprocessor { // This class will process a normal map and add the value of average normal length to the blue or alpha channel // The texture is save as BC7. // Tangent space normal map: BC7 RGB (normal xy - average normal length) // Object space normal map: BC7 RGBA (normal xyz - average normal length) static string s_Suffix = "_NA"; //static string s_SuffixOS = "_OSNA"; // Suffix for object space case - TODO void OnPreprocessTexture() { // Any texture with _NA suffix will store average normal lenght in alpha if (assetPath.IndexOf(s_Suffix, StringComparison.InvariantCultureIgnoreCase) != -1) { // Make sure we don't convert as a normal map. TextureImporter textureImporter = (TextureImporter)assetImporter; textureImporter.convertToNormalmap = false; textureImporter.alphaSource = TextureImporterAlphaSource.None; textureImporter.mipmapEnabled = true; textureImporter.textureCompression = TextureImporterCompression.CompressedHQ; // This is BC7 for Mac/PC #pragma warning disable 618 // remove obsolete warning for this one textureImporter.linearTexture = true; // Says deprecated but won't work without it. #pragma warning restore 618 textureImporter.sRGBTexture = false; // But we're setting the new property just in case it changes later... } } private static Color GetColor(Color[] source, int x, int y, int width, int height) { x = (x + width) % width; y = (y + height) % height; int index = y * width + x; var c = source[index]; return c; } private static Vector3 GetNormal(Color[] source, int x, int y, int width, int height) { Vector3 n = (Vector4)GetColor(source, x, y, width, height); n = 2.0f * n - Vector3.one; n.Normalize(); return n; } private static Vector3 GetAverageNormal(Color[] source, int x, int y, int width, int height, int texelFootprint) { Vector3 averageNormal = new Vector3(0, 0, 0); // Calculate the average color over the texel footprint. for (int i = 0; i < texelFootprint; ++i) { for (int j = 0; j < texelFootprint; ++j) { averageNormal += GetNormal(source, x + i, y + j, width, height); } } averageNormal /= (texelFootprint * texelFootprint); return averageNormal; } void OnPostprocessTexture(Texture2D texture) { if (assetPath.IndexOf(s_Suffix, StringComparison.InvariantCultureIgnoreCase) != -1) { // Based on The Order : 1886 SIGGRAPH course notes implementation. Sample all normal map // texels from the base mip level that are within the footprint of the current mipmap texel. Color[] source = texture.GetPixels(0); for (int m = 1; m < texture.mipmapCount; m++) { Color[] c = texture.GetPixels(m); int mipWidth = Math.Max(1, texture.width >> m); int mipHeight = Math.Max(1, texture.height >> m); for (int x = 0; x < mipWidth; ++x) { for (int y = 0; y < mipHeight; ++y) { int texelFootprint = 1 << m; Vector3 averageNormal = GetAverageNormal(source, x * texelFootprint, y * texelFootprint, texture.width, texture.height, texelFootprint); // Store the normal length for the average normal. int outputPosition = y * mipWidth + x; // Clamp to avoid any issue (TODO: Check this) // Write into the blue channel float averageNormalLength = Math.Max(0.0f, Math.Min(1.0f, averageNormal.magnitude)); c[outputPosition].b = averageNormalLength; c[outputPosition].a = 1.0f; } } texture.SetPixels(c, m); } // Now overwrite the first mip average normal channel - order is important as above we read the mip0 // For mip 0, set the normal length to 1. { Color[] c = texture.GetPixels(0); for (int i = 0; i < c.Length; i++) { c[i].b = 1.0f; c[i].a = 1.0f; } texture.SetPixels(c, 0); } } } }