读取包含Heightmap的.raw文件

Question

I am using the libnoise library to generate a random terrain and saving it in a .raw file that has its elevation points measured in meters. This terrain file contains 16-bit signed big-endian values, in row-major order, ordered south to north. This is the code I am using for reading the file.

struct HeightMapType
    {
        float x, y, z;
        float nx, ny, nz;
        float r, g, b;
    };

bool Terrain::LoadRawFile()
{
    int error, i, j, index;
    FILE* filePtr;
    unsigned long long imageSize, count;
    unsigned short* rawImage;


    // Create the float array to hold the height map data.
    m_heightMap = new HeightMapType[m_terrainWidth * m_terrainHeight];
    if(!m_heightMap)
    {
        return false;
    }

    // Open the 16 bit raw height map file for reading in binary.
    error = fopen_s(&filePtr, m_terrainFilename, "rb");
    if(error != 0)
    {
        return false;
    }

    // Calculate the size of the raw image data.
    imageSize = m_terrainHeight * m_terrainWidth;

    // Allocate memory for the raw image data.
    rawImage = new unsigned short[imageSize];
    if(!rawImage)
    {
        return false;
    }

    // Read in the raw image data.
    count = fread(rawImage, sizeof(unsigned short), imageSize, filePtr);
    if(count != imageSize)
    {
        return false;
    }

    // Close the file.
    error = fclose(filePtr);
    if(error != 0)
    {
        return false;
    }

    // Copy the image data into the height map array.
    for(j=0; j<m_terrainHeight; j++)
    {
        for(i=0; i<m_terrainWidth; i++)
        {
            index = (m_terrainWidth * j) + i;

            // Store the height at this point in the height map array.
            m_heightMap[index].y = (float)rawImage[index];
        }
    }

    // Release the bitmap image data.
    delete [] rawImage;
    rawImage = 0;

    // Release the terrain filename now that it has been read in.
    delete [] m_terrainFilename;
    m_terrainFilename = 0;

    return true;
}

The code does not return any error but this is the result rendered: rawFileRendering .

I tested the code with another heightmap saved in a raw file (given by rastertek) and it works.

Do you know why the rendered scene is like this? Thank you for your help.

Answer 1

Two problems:

1. You use unsigned short , but you said in the description that the numbers are signed. So you should use signed short instead
2. You don't do anything with endianness. If you are on a little endian machine, you should convert your values from big endian to little endian.

You can convert endianness with this:

short endianConvert(short x) {
    unsigned short v = (unsigned short)x;
    return (short)(v>>8|v<<8);
}