Cubemaps turn black OpenGL GLSL Java LWJGL

Question

Recently I tried to add cubemaps to my 3D-rendering engine. The objects with a cubemap now turn completely black. This is how I load my cubemap:

public static int loadCubeMap(String filename)
{
    int id = GL11.glGenTextures();

    GL13.glActiveTexture(GL13.GL_TEXTURE0);
    GL11.glBindTexture(GL13.GL_TEXTURE_CUBE_MAP, id);

    for(int i = 0; i < CUBEMAP_NAMES.length; i++)
    {
        TextureData data = decodeTextureFile(CUBEMAPS_LOCATION + filename + "/" + CUBEMAP_NAMES[i]);
        GL11.glTexImage2D(GL13.GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL11.GL_RGBA, data.getWidth(), data.getHeight(), 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, data.getBuffer());
    }
    GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
    GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR); 
    GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
    GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);
    return id;
}

TextureData class only contains: int width, height and a ByteBuffer buffer

private static TextureData decodeTextureFile(String fileName)
{
    int width = 0;
    int height = 0;
    ByteBuffer buffer = null;
    try 
    {
        FileInputStream in = new FileInputStream(TEXTURES_LOCATION + fileName + ".png");
        PNGDecoder decoder = new PNGDecoder(in);
        width = decoder.getWidth();
        height = decoder.getHeight();
        buffer = ByteBuffer.allocateDirect(4 * width * height);
        decoder.decode(buffer, width * 4, Format.RGBA);
        buffer.flip();
        in.close();
    } catch (Exception e) 
    {
        e.printStackTrace();
    }
    return new TextureData(width, height, buffer);
}

This is how I load the cubemap to the samplerCube cubemap[i] in the fragment shader:

public void loadCubeMap(int id, CubeMap cubemap, int cubemapid)
{
    if(cubemap != null)
    {
        super.loadTexture(location_cubemaps[cubemapid], cubemap.id, id, GL13.GL_TEXTURE_CUBE_MAP);
        super.loadFloat(location_cubemap_intensity[id], cubemap.intensity);
    }else
    {
        super.loadFloat(location_cubemap_intensity[id], 0.0f);  
    }
}

in super class:

protected void loadTexture(int location, int texture, int i, int texturetype)
{
    loadInt(location, i+1);
    GL13.glActiveTexture(GL13.GL_TEXTURE0 + i);
    GL11.glBindTexture(texturetype, texture);
}

And this is my fragment shader:

#version 400 core

  in vec4 color;
  in vec2 texCoord0;
  in vec3 surface_normal;
  in vec3 to_light_vector;
  in vec3 world_position_out;
  out vec4 out_Color;


  uniform sampler2D sampler0;

  uniform samplerCube cubemap[3];

  uniform vec3 lightColor;

  uniform float cubemap_intensity[3];

  uniform int hasTexture;

  void main(void)
   {
      vec3 unitNormal = normalize(surface_normal);
   vec3 unitLight  = normalize(to_light_vector);

   float nDot1 = dot(unitNormal, unitLight);
   float brightness = max(nDot1, 0.02);

   vec3 diffuse = color.xyz * brightness * lightColor * color.xyz;
   vec4 textureColor = texture(sampler0, texCoord0.xy);
   if(textureColor.a < 0.5)
       discard;
   vec4 shadedTextureColor = brightness * vec4(lightColor, 1) * textureColor;
    vec4 coloredShadedTexture = mix(vec4(diffuse, 1), shadedTextureColor, textureColor.a * hasTexture);

   vec4 reflectionColor = texture(cubemap[0], world_position_out);
   vec4 refractionColor;
   vec4 cubemapColor;

   out_Color = reflectionColor;
  }

Answer 1

What a dump question. I put the cubemap to the wrong samplerCube. I assigned the map to cubemap[1] not cubemap[0]. Great example of "I wouldn't do something like this. The error must be somewhere in the OpenGL code!" :D