如果我有纹理,那么是否可以为此纹理生成法线贴图,以便将其用于凹凸贴图?

或通常如何制作法线贴图?

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,您还可以放置常规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,例如获取高分辨率模型,使其变为低分辨率,然后进行射线转换以查看低分辨率模型模拟更高的法线应该具有的法线。

对于高度图到法线图,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强调或“深度”。然后,将x,y和z放入 vector 中,对其进行归一化,此时您将拥有法线。将其编码到像素中就可以完成。

这是一些较旧的不完整代码,说明了这一点:

// 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/

10-11 21:58
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