Reading .raw file containing Heightmap

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);
}