-- on gl surface creation --

GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

GLES20.glFrontFace(GLES20.GL_CW);
GLES20.glCullFace(GLES20.GL_BACK);
GLES20.glEnable(GLES20.GL_CULL_FACE);

GLES20.glDepthFunc(GLES20.GL_LEQUAL);
GLES20.glEnable(GLES20.GL_DEPTH_TEST);

GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);
GLES20.glEnable(GLES20.GL_BLEND);

-- on gl surface changed --

GLES20.glViewport(0, 0, width, height);

-- activating 'material' before draw --

GLES20.glUseProgram(shaderId);
checkGlError("glUseProgram");

GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);

-- on draw --

alphaHandle = GLES20.glGetAttribLocation(material.getShader(), "aAlpha");
checkGlError("glGetAttribLocation aAlpha");
if (alphaHandle == GL_ERROR)
{
    throw new RuntimeException("Could not get attribute location for aAlpha");
}

GLES20.glVertexAttrib1f(alphaHandle, alpha);
checkGlError("glVertexAttrib1f alphaHandle");

/*
 * GRID POSITION
 */

positionHandle = GLES20.glGetAttribLocation(material.getShader(), "aPosition");
checkGlError("glGetAttribLocation aPosition");
if (positionHandle == GL_ERROR)
{
    throw new RuntimeException("Could not get attribute location for uPosition");
}

GLES20.glVertexAttrib3f(positionHandle, position.x, position.y, position.z);
checkGlError("glVertexAttrib3f positionHandle");

/*
 * VERTICES
 */

vertexHandle = GLES20.glGetAttribLocation(material.getShader(), "aVertex");
checkGlError("glGetAttribLocation aVertex");
if (vertexHandle == GL_ERROR)
{
    throw new RuntimeException("Could not get attrib location for aVertex");
}

GLES20.glEnableVertexAttribArray(vertexHandle);
checkGlError("glEnableVertexAttribArray vertexHandle");

mesh.getVertexBuffer().position(TRIANGLE_VERTICES_DATA_POS_OFFSET);
GLES20.glVertexAttribPointer(vertexHandle, 3, GLES20.GL_FLOAT, false, TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mesh.getVertexBuffer());
checkGlError("glVertexAttribPointer vertexHandle");

/*
 * TEXTURE COORDS
 */

textureHandle = GLES20.glGetAttribLocation(material.getShader(), "aTextureCoord");
checkGlError("glGetAttribLocation aTextureCoord");
if (textureHandle == GL_ERROR)
{
    throw new RuntimeException("Could not get attrib location for aTextureCoord");
}

GLES20.glEnableVertexAttribArray(textureHandle);
checkGlError("glEnableVertexAttribArray textureHandle");

mesh.getVertexBuffer().position(TRIANGLE_VERTICES_DATA_UV_OFFSET);
GLES20.glVertexAttribPointer(textureHandle, 2, GLES20.GL_FLOAT, false, TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mesh.getVertexBuffer());
checkGlError("glVertexAttribPointer textureHandle");

/*
 * MATRICES
 */

mvpMatrixHandle = GLES20.glGetUniformLocation(material.getShader(), "uMVPMatrix");
checkGlError("glGetUniformLocation uMVPMatrix");
if (mvpMatrixHandle == GL_ERROR)
{
    throw new RuntimeException("Could not get attrib location for uMVPMatrix");
}

Matrix.setIdentityM(mMatrix, 0);

GLES20.glUniformMatrix4fv(mvpMatrixHandle, 1, false, DroidGL.getActiveCamera().getModelViewProjectionMatrix(mMatrix), 0);

/*
 * DRAW
 */

GLES20.glDrawElements(GLES20.GL_TRIANGLES, mesh.getNumIndices(), GLES20.GL_UNSIGNED_SHORT, mesh.getIndexBuffer());