如果我有一个纹理，是否可以为这个纹理生成一个法线贴图，以便它可以用于凹凸贴图？

或者法线贴图通常是如何制作的？

最佳答案

是的。好吧，有点。法线贴图可以从高度贴图准确地制作出来。通常，您也可以放置规则纹理并获得不错的效果。请记住，还有其他制作法线贴图的方法，例如采用高分辨率模型，使其成为低分辨率，然后进行光线转换以查看低分辨率模型模拟较高模型的法线应该是多少。

对于高度贴图到法线贴图，您可以使用 Sobel Operator .该运算符可以在 x 方向上运行，告诉您法线的 x 分量，然后在 y 方向上运行，告诉您 y 分量。您可以使用 1.0/strength 计算 z，其中强度是法线贴图的重点或“深度”。然后，将 x、y 和 z 放入一个 vector 中，对其进行归一化，然后在该点获得法线。将其编码到像素中即可完成。

这里有一些较旧的不完整代码可以证明这一点:

// pretend types, something like this
struct pixel
{
    uint8_t red;
    uint8_t green;
    uint8_t blue;
};

struct vector3d; // a 3-vector with doubles
struct texture; // a 2d array of pixels

// determine intensity of pixel, from 0 - 1
const double intensity(const pixel& pPixel)
{
    const double r = static_cast<double>(pPixel.red);
    const double g = static_cast<double>(pPixel.green);
    const double b = static_cast<double>(pPixel.blue);

    const double average = (r + g + b) / 3.0;

    return average / 255.0;
}

const int clamp(int pX, int pMax)
{
    if (pX > pMax)
    {
        return pMax;
    }
    else if (pX < 0)
    {
        return 0;
    }
    else
    {
        return pX;
    }
}

// transform -1 - 1 to 0 - 255
const uint8_t map_component(double pX)
{
    return (pX + 1.0) * (255.0 / 2.0);
}

texture normal_from_height(const texture& pTexture, double pStrength = 2.0)
{
    // assume square texture, not necessarily true in real code
    texture result(pTexture.size(), pTexture.size());

    const int textureSize = static_cast<int>(pTexture.size());
    for (size_t row = 0; row < textureSize; ++row)
    {
        for (size_t column = 0; column < textureSize; ++column)
        {
            // surrounding pixels
            const pixel topLeft = pTexture(clamp(row - 1, textureSize), clamp(column - 1, textureSize));
            const pixel top = pTexture(clamp(row - 1, textureSize), clamp(column, textureSize));
            const pixel topRight = pTexture(clamp(row - 1, textureSize), clamp(column + 1, textureSize));
            const pixel right = pTexture(clamp(row, textureSize), clamp(column + 1, textureSize));
            const pixel bottomRight = pTexture(clamp(row + 1, textureSize), clamp(column + 1, textureSize));
            const pixel bottom = pTexture(clamp(row + 1, textureSize), clamp(column, textureSize));
            const pixel bottomLeft = pTexture(clamp(row + 1, textureSize), clamp(column - 1, textureSize));
            const pixel left = pTexture(clamp(row, textureSize), clamp(column - 1, textureSize));

            // their intensities
            const double tl = intensity(topLeft);
            const double t = intensity(top);
            const double tr = intensity(topRight);
            const double r = intensity(right);
            const double br = intensity(bottomRight);
            const double b = intensity(bottom);
            const double bl = intensity(bottomLeft);
            const double l = intensity(left);

            // sobel filter
            const double dX = (tr + 2.0 * r + br) - (tl + 2.0 * l + bl);
            const double dY = (bl + 2.0 * b + br) - (tl + 2.0 * t + tr);
            const double dZ = 1.0 / pStrength;

            math::vector3d v(dX, dY, dZ);
            v.normalize();

            // convert to rgb
            result(row, column) = pixel(map_component(v.x), map_component(v.y), map_component(v.z));
        }
    }

    return result;
}

关于c++ - 可以从纹理生成法线贴图吗？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/2368728/