Merender dua objek di OpenGL ES

Saya mencoba menambahkan dua objek, yang dibuat dari satu bagian, tetapi karena saya perlu mewarnai setiap bagian, saya memisahkannya. Saya telah mencoba merender satu bagian yang berfungsi, tetapi setelah itu saya mencoba merender keduanya namun tidak menghasilkan apa-apa.

        glGenVertexArraysOES(1, &_boxVAO);
        glBindVertexArrayOES(_boxVAO);

        int sizeOfFaces = myMesh_m.faces.size() * sizeof(ObjMeshFace);
        glGenBuffers(1, &_boxBuffer);
        glBindBuffer(GL_ARRAY_BUFFER, _boxBuffer);
        glBufferData(GL_ARRAY_BUFFER, sizeOfFaces, &(myMesh_m.faces[0]), GL_STATIC_DRAW);

        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(ObjMeshVertex), 0);
        glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(ObjMeshVertex), (void*)(sizeof(Vector3f) + sizeof(Vector2f)));

        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(2);

        sizeOfFaces = myMesh_p.faces.size() * sizeof(ObjMeshFace);
        glGenBuffers(1, &_boxBuffer_sec);
        glBindBuffer(GL_ARRAY_BUFFER, _boxBuffer_sec);
        glBufferData(GL_ARRAY_BUFFER, sizeOfFaces, &(myMesh_p.faces[0]), GL_STATIC_DRAW);

        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(ObjMeshVertex), 0);
        glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(ObjMeshVertex), (void*)(sizeof(Vector3f) + sizeof(Vector2f)));

        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(2);

        glBindVertexArrayOES(0);

Menggambar:

            glBindVertexArrayOES( _boxVAO);
            glUniform2fv(uniforms[UNIFORM_NORMAL_MATRIX], 1, color);
            glUniformMatrix4fv(uniforms[UNIFORM_MODELVIEWPROJECTION_MATRIX], 1, GL_FALSE, _modelViewProjectionMatrix.m);
            glDrawArrays(GL_TRIANGLES, 0, pointerSize_m*3);

Shader.vsh

attribute vec4 position;
attribute vec3 normal;

varying lowp vec4 colorVarying;

uniform mat4 modelViewProjectionMatrix;
uniform mat3 normalMatrix;

void main()
{
    vec3 eyeNormal = normalize(normalMatrix * normal);
    vec3 lightPosition = vec3(1.0, 1.0, 1.0);
    vec4 diffuseColor = vec4(1, 0.4, 1.0, 1.0);

    float nDotVP = max(0.0, dot(eyeNormal, normalize(lightPosition)));

    colorVarying = diffuseColor * nDotVP;

    gl_Position = modelViewProjectionMatrix * position;
}

Shader.fsh

//varying lowp vec4 colorVarying;
uniform lowp vec4 color;


void main()
{
//    gl_FragColor = colorVarying;
    gl_FragColor = color;

}

Mengapa ini gagal? Selanjutnya bagaimana cara mewarnai setiap objek?