OpenGL ES 2.0 - Textures always black

Question

I've been reading a lot about textures in Open GL ES 2.0 today. My problem is, that they are all black.

My code:

To generate a texture from a bitmap:

private void generateTexture(Bitmap bmp) {
    final int[] textureHandle = new int[1];

    Log.d(TAG, "Generating texture handle");
    GLES20.glGenTextures(1, textureHandle, 0);

    if (textureHandle[0] != 0) {

        Log.d(TAG, "binding texture to " + textureHandle[0]);
        // Bind to the texture in OpenGL
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);
        Log.d(TAG, "GLError@bindTex=" + GLES20.glGetError());

        // Set filtering
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,
                GLES20.GL_CLAMP_TO_EDGE);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,
                GLES20.GL_CLAMP_TO_EDGE);

        Log.d(TAG, "Loading bitmap into texture");
        // Load the bitmap into the bound texture.
        GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bmp, 0);

        Log.d(TAG, "GLError@texImg2D=" + GLES20.glGetError());

        Log.d(TAG, "Recycle bitmap");
        // Recycle the bitmap, since its data has been loaded into OpenGL.
        bmp.recycle();
    }

There are no errors in my logcat, everything seems to be like it's supposed to.

How I use the texture:

    if (mShader instanceof Texture2DShader && mTextureBuffer != null) {
        // activate texture
        Log.d(TAG, "Passing texture stuff");
        mTextureBuffer.position(0);
        Log.d(TAG, "Activate Texture");
        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
        Log.d(TAG, "Binding texture -> " + mTexture.getHandle());
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTexture.getHandle());

        if (mShader.getGLLocation(BaseShader.U_TEXTURE) != -1) {
            Log.d(TAG, "Passing u_Texture");
            GLES20.glUniform1i(mShader.getGLLocation(BaseShader.U_TEXTURE), 0);
        }

        if (mShader.getGLLocation(BaseShader.A_TEXCOORDINATE) != -1) {
            Log.d(TAG, "Passing a_TexCoordinate");
            GLES20.glVertexAttribPointer(mShader.getGLLocation(BaseShader.A_TEXCOORDINATE), 2, GLES20.GL_FLOAT, false, 0, mTextureBuffer);
            GLES20.glEnableVertexAttribArray(mShader.getGLLocation(BaseShader.A_TEXCOORDINATE));
        }
        Log.d(TAG, "Texture stuff passed.");
        Log.d(TAG, "Error = " + GLES20.glGetError());
    }

Logcat says something like this:

D/TextureCube﹕ Activate Texture
D/TextureCube﹕ Binding texture -> 3
D/TextureCube﹕ Passing u_Texture
D/TextureCube﹕ Passing a_TexCoordinate
D/TextureCube﹕ Texture stuff passed.
D/TextureCube﹕ Error = 0

So no error, seems to be working?

My shaders:

Fragment shader:

precision mediump float;        // Set the default precision to medium. We don't need as high of a
                                // precision in the fragment shader.
uniform vec3 u_LightPos;        // The position of the light in eye space.
uniform vec4 u_Light;
uniform vec4 u_Ambient;
uniform vec3 u_LightDirection;
uniform vec3 u_CameraPos;
uniform sampler2D u_Texture;

//varying vec4 v_Ambient;        // Ambient light factor!
varying vec2 v_TexCoordinate;
varying vec3 v_Position;        // Interpolated position for this fragment.
varying vec4 v_Color;           // This is the color from the vertex shader interpolated across the triangle per fragment.
varying vec3 v_Normal;          // Interpolated normal for this fragment.
//varying vec3 v_CameraPosition;

// The entry point for our fragment shader.
void main()
{
    // Will be used for attenuation.
    float distance = length(u_LightPos - v_Position);

    // Get a lighting direction vector from the light to the vertex.
    vec3 lightVector = normalize(u_LightPos - v_Position);

    // Calculate the dot product of the light vector and vertex normal. If the normal and light vector are
    // pointing in the same direction then it will get max illumination.
    float diffuse = max(dot(v_Normal, lightVector), 0.1);

    // Add attenuation. (used to be    0.25)
    diffuse = diffuse * (1.0 / (1.0 + (0.25 * distance * distance)));

    // calculate specular light!
    //vec3 lightDirection = -u_LightDirection;
    //vec3 vertexToEye = normalize(u_CameraPos - v_CameraPos);
    //vec3 lightReflect = normalize(reflect(u_LightDirection, v_Normal));
    //float specularFactor = dot(vertexToEye, lightReflect);



    // Multiply the color by the diffuse illumination level to get final output color.
    //
    gl_FragColor = v_Color * (u_Ambient + (diffuse * u_Light) * texture2D(u_Texture, v_TexCoordinate));
}

Vertex Shader:

uniform mat4 u_MVPMatrix;       // A constant representing the combined model/view/projection matrix.
uniform mat4 u_MVMatrix;        // A constant representing the combined model/view matrix.

attribute vec4 a_Position;      // Per-vertex position information we will pass in.
attribute vec4 a_Color;         // Per-vertex color information we will pass in.
attribute vec3 a_Normal;        // Per-vertex normal information we will pass in.
attribute vec2 a_TexCoordinate;

varying vec2 v_TexCoordinate;
varying vec3 v_Position;        // This will be passed into the fragment shader.
varying vec4 v_Color;           // This will be passed into the fragment shader.
varying vec3 v_Normal;          // This will be passed into the fragment shader.
//varying vec3 v_CameraPosition;
//varying vec4 v_Ambient;         // Pass the ambient color to the fragment shader.

// The entry point for our vertex shader.
void main()
{
    // Transform the vertex into eye space.
    v_Position = vec3(u_MVMatrix * a_Position);

    v_TexCoordinate = a_TexCoordinate;

    // Pass through the color.
    v_Color = a_Color;

    // Transform the normal's orientation into eye space.
    v_Normal = vec3(u_MVMatrix * vec4(a_Normal, 0.0));
    //v_CameraPos = vec3(u_MVMatrix * vec4(u_CameraPos, 0.0));
//    v_CameraPosition = u_CameraPos;

    // gl_Position is a special variable used to store the final position.
    // Multiply the vertex by the matrix to get the final point in normalized screen coordinates.
    gl_Position = u_MVPMatrix * a_Position;
}

Seems like texture2D returns a zero vector in the fragment shader, since if I simply write gl_FragColor = vec4(0.5,0.5,0.5,1.0) + texture2D(..) it is drawn.

I've already looked at countless questions here on SO as well as other websites, I know this exact question has been asked a couple of times, but no matter what I've tried - it did not help.

I've already downscaled my texture to 512x512, then 256x256, and even lower up to 64x64 but no changes. I've printed out my texture handlers, checked for GL errors, etc. but nothing.

EDIT:

At first I've been trying to load the texture from R.raw, then moved it to R.drawable, but no change.

EDIT 2: Cube vertices/normals/texture/color declaration:

private final float[] mCubePosition =  {

                // Front face
                -1.0f, 1.0f, 1.0f,
                -1.0f, -1.0f, 1.0f,
                1.0f, 1.0f, 1.0f,
                -1.0f, -1.0f, 1.0f,
                1.0f, -1.0f, 1.0f,
                1.0f, 1.0f, 1.0f,

                // Right face
                1.0f, 1.0f, 1.0f,
                1.0f, -1.0f, 1.0f,
                1.0f, 1.0f, -1.0f,
                1.0f, -1.0f, 1.0f,
                1.0f, -1.0f, -1.0f,
                1.0f, 1.0f, -1.0f,

                // Back face
                1.0f, 1.0f, -1.0f,
                1.0f, -1.0f, -1.0f,
                -1.0f, 1.0f, -1.0f,
                1.0f, -1.0f, -1.0f,
                -1.0f, -1.0f, -1.0f,
                -1.0f, 1.0f, -1.0f,

                // Left face
                -1.0f, 1.0f, -1.0f,
                -1.0f, -1.0f, -1.0f,
                -1.0f, 1.0f, 1.0f,
                -1.0f, -1.0f, -1.0f,
                -1.0f, -1.0f, 1.0f,
                -1.0f, 1.0f, 1.0f,

                // Top face
                -1.0f, 1.0f, -1.0f,
                -1.0f, 1.0f, 1.0f,
                1.0f, 1.0f, -1.0f,
                -1.0f, 1.0f, 1.0f,
                1.0f, 1.0f, 1.0f,
                1.0f, 1.0f, -1.0f,

                // Bottom face
                1.0f, -1.0f, -1.0f,
                1.0f, -1.0f, 1.0f,
                -1.0f, -1.0f, -1.0f,
                1.0f, -1.0f, 1.0f,
                -1.0f, -1.0f, 1.0f,
                -1.0f, -1.0f, -1.0f,
        };

// R, G, B, A
private final float[] mCubeColors =
        {
                // Front face (red)
                1.0f, 0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, 0.0f, 1.0f,

                // Right face (green)
                0.0f, 1.0f, 0.0f, 1.0f,
                0.0f, 1.0f, 0.0f, 1.0f,
                0.0f, 1.0f, 0.0f, 1.0f,
                0.0f, 1.0f, 0.0f, 1.0f,
                0.0f, 1.0f, 0.0f, 1.0f,
                0.0f, 1.0f, 0.0f, 1.0f,

                // Back face (blue)
                0.0f, 0.0f, 1.0f, 1.0f,
                0.0f, 0.0f, 1.0f, 1.0f,
                0.0f, 0.0f, 1.0f, 1.0f,
                0.0f, 0.0f, 1.0f, 1.0f,
                0.0f, 0.0f, 1.0f, 1.0f,
                0.0f, 0.0f, 1.0f, 1.0f,

                // Left face (yellow)
                1.0f, 1.0f, 0.0f, 1.0f,
                1.0f, 1.0f, 0.0f, 1.0f,
                1.0f, 1.0f, 0.0f, 1.0f,
                1.0f, 1.0f, 0.0f, 1.0f,
                1.0f, 1.0f, 0.0f, 1.0f,
                1.0f, 1.0f, 0.0f, 1.0f,

                // Top face (cyan)
                0.0f, 1.0f, 1.0f, 1.0f,
                0.0f, 1.0f, 1.0f, 1.0f,
                0.0f, 1.0f, 1.0f, 1.0f,
                0.0f, 1.0f, 1.0f, 1.0f,
                0.0f, 1.0f, 1.0f, 1.0f,
                0.0f, 1.0f, 1.0f, 1.0f,

                // Bottom face (magenta)
                1.0f, 0.0f, 1.0f, 1.0f,
                1.0f, 0.0f, 1.0f, 1.0f,
                1.0f, 0.0f, 1.0f, 1.0f,
                1.0f, 0.0f, 1.0f, 1.0f,
                1.0f, 0.0f, 1.0f, 1.0f,
                1.0f, 0.0f, 1.0f, 1.0f
        };

private final float[] mCubeNormals =
        {
                // Front face
                0.0f, 0.0f, 1.0f,
                0.0f, 0.0f, 1.0f,
                0.0f, 0.0f, 1.0f,
                0.0f, 0.0f, 1.0f,
                0.0f, 0.0f, 1.0f,
                0.0f, 0.0f, 1.0f,

                // Right face
                1.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.0f,

                // Back face
                0.0f, 0.0f, -1.0f,
                0.0f, 0.0f, -1.0f,
                0.0f, 0.0f, -1.0f,
                0.0f, 0.0f, -1.0f,
                0.0f, 0.0f, -1.0f,
                0.0f, 0.0f, -1.0f,

                // Left face
                -1.0f, 0.0f, 0.0f,
                -1.0f, 0.0f, 0.0f,
                -1.0f, 0.0f, 0.0f,
                -1.0f, 0.0f, 0.0f,
                -1.0f, 0.0f, 0.0f,
                -1.0f, 0.0f, 0.0f,

                // Top face
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, 0.0f,

                // Bottom face
                0.0f, -1.0f, 0.0f,
                0.0f, -1.0f, 0.0f,
                0.0f, -1.0f, 0.0f,
                0.0f, -1.0f, 0.0f,
                0.0f, -1.0f, 0.0f,
                0.0f, -1.0f, 0.0f
        };

private final float[] mCubeTexture =
        {
                // Front face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f,

                // Right face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f,

                // Back face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f,

                // Left face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f,

                // Top face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f,

                // Bottom face
                0.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f,
                1.0f, 0.0f
        };

EDIT 3: Texture Coordinates as Colors to see if they are being transmitted:

gl_FragColor = vec4(v_TexCoordinate.x, v_TexCoordinate.y, 0, 1); in the fragment shader results in:

Answer 1

this is a very common issue then you do not work with power of 2 textures (pixel wise).

To not repeat here the same already provided solution, please have a look to my previous response on this matter.

Android OpenGL2.0 showing black textures

I hope this will solve your issue.

Cheers Maurizio

Answer 2

Ok, I found the solution. I was again confused by the way the OpenGL thread works. I was loading the Bitmap in a thread, then using glView.post(); to post a Runnable back to the (what I thought) OpenGL thread, where the texture was supposed to be generated and bound to the bitmap.

This does not work. What I should have done is:

GLSurfaceView glView = ...;
glView.queueEvent(new Runnable() {
  @Override
  public void run() {
   generateTexture(bitmap);
  }
});

Where in generateTexture, I execute all the GLES20.generateTexture etc stuff, since with queueEvent, it's again on the real OpenGL thread, not on the UI thread.

Apparently, my code for using the texture has been correct. Thanks for your help.