3D model does not appear when rendering

Question

I'm using Vuforia to place a 3D model on an image target. I have created a common C++ solution to work on both Android and iOS. It works on Android, but I can't get the 3D model to appear in iOS. It tracks the image target perfectly, but there's no sign of the 3D model. The 3D model I'm using can be found here.

This is how I'm doing:

This method is called by Vuforia every time the screen needs to be rendered:

- (void)renderFrameQCAR
{
    [self setFramebuffer];
    [[ObjectController getInstance] getObjectInstance]->renderFrame();
    [self presentFramebuffer];
}

This is the setFramebuffer method (Objective-C++):

- (void)setFramebuffer
{
    if (context) {
        [EAGLContext setCurrentContext:context];

        if (!defaultFramebuffer) {
            [self performSelectorOnMainThread:@selector(createFramebuffer) withObject:self waitUntilDone:YES];
        }

#ifdef USE_OPENGL1
        glBindFramebufferOES(GL_FRAMEBUFFER_OES, defaultFramebuffer);
#else
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
#endif
    }
}

This is the renderFrame method (C++):

void IDRObject::renderFrame()
{
    // Clear color and depth buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // Get the state from QCAR and mark the beginning of a rendering section
    QCAR::State state = QCAR::Renderer::getInstance().begin();

    // Explicitly render the Video Background
    QCAR::Renderer::getInstance().drawVideoBackground();

#ifdef DEVICE_OPENGL_1
    // Set GL11 flags:
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    glEnable(GL_TEXTURE_2D);
    glDisable(GL_LIGHTING);

#endif

    glEnable(GL_DEPTH_TEST);

    // We must detect if background reflection is active and adjust the culling direction.
    // If the reflection is active, this means the post matrix has been reflected as well,
    // therefore standard counter clockwise face culling will result in "inside out" models.
    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
    if(QCAR::Renderer::getInstance().getVideoBackgroundConfig().mReflection == QCAR::VIDEO_BACKGROUND_REFLECTION_ON)
        glFrontFace(GL_CW);  //Front camera
    else
        glFrontFace(GL_CCW);   //Back camera

    SampleUtils::checkGlError("gl start setup stuff");
    // Did we find any trackables this frame?
    for(int tIdx = 0; tIdx < state.getNumTrackableResults(); tIdx++)
    {
        // Get the trackable:
        const QCAR::TrackableResult* result = state.getTrackableResult(tIdx);
        const QCAR::Trackable& trackable = result->getTrackable();
        QCAR::Matrix44F modelViewMatrix = QCAR::Tool::convertPose2GLMatrix(result->getPose());

        // Choose the texture based on the target name:
        int textureIndex;
        if (strcmp(trackable.getName(), "chips") == 0)
        {
            textureIndex = 0;
        }
        else if (strcmp(trackable.getName(), "stones") == 0)
        {
            textureIndex = 1;
        }
        else
        {
            textureIndex = 2;
        }

        const Texture* const thisTexture = textures[textureIndex];

#ifdef DEVICE_OPENGL_1
        // Load projection matrix:
        glMatrixMode(GL_PROJECTION);
        glLoadMatrixf(projectionMatrix.data);

        // Load model view matrix:
        glMatrixMode(GL_MODELVIEW);
        glLoadMatrixf(modelViewMatrix.data);
        glTranslatef(0.f, 0.f, kObjectScale);
        glScalef(kObjectScale, kObjectScale, kObjectScale);

        // Draw object:
        glBindTexture(GL_TEXTURE_2D, thisTexture->mTextureID);
        glTexCoordPointer(2, GL_FLOAT, 0, (const GLvoid*) &teapotTexCoords[0]);
        glVertexPointer(3, GL_FLOAT, 0, (const GLvoid*) &teapotVertices[0]);
        glNormalPointer(GL_FLOAT, 0,  (const GLvoid*) &teapotNormals[0]);
        glDrawElements(GL_TRIANGLES, NUM_TEAPOT_OBJECT_INDEX, GL_UNSIGNED_SHORT,
                   (const GLvoid*) &teapotIndices[0]);

#else


        QCAR::Matrix44F modelViewProjection;

        SampleUtils::translatePoseMatrix(0.0f, 0.0f, kObjectScale, &modelViewMatrix.data[0]);
        SampleUtils::scalePoseMatrix(kObjectScale, kObjectScale, kObjectScale, &modelViewMatrix.data[0]);
        SampleUtils::multiplyMatrix(&projectionMatrix.data[0], &modelViewMatrix.data[0], &modelViewProjection.data[0]);

        glUseProgram(shaderProgramID);

        glVertexAttribPointer(vertexHandle, 3, GL_FLOAT, GL_FALSE, 0, (const GLvoid*) &teapotVertices[0]);
        glVertexAttribPointer(normalHandle, 3, GL_FLOAT, GL_FALSE, 0, (const GLvoid*) &teapotNormals[0]);
        glVertexAttribPointer(textureCoordHandle, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid*) &teapotTexCoords[0]);

        glEnableVertexAttribArray(vertexHandle);
        glEnableVertexAttribArray(normalHandle);
        glEnableVertexAttribArray(textureCoordHandle);

        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, thisTexture->mTextureID);

        glUniformMatrix4fv(mvpMatrixHandle, 1, GL_FALSE, (GLfloat*)&modelViewProjection.data[0] );
        glUniform1i(texSampler2DHandle, 0 /*GL_TEXTURE0*/);
        glDrawElements(GL_TRIANGLES, NUM_TEAPOT_OBJECT_INDEX, GL_UNSIGNED_SHORT, (const GLvoid*) &teapotIndices[0]);

        LOG("Tracking awesome targets.\n");
        SampleUtils::checkGlError("ImageTargets renderFrame\n");
#endif

    }

    glDisable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);

#ifdef DEVICE_OPENGL_1
    glDisable(GL_TEXTURE_2D);
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
#else
    glDisableVertexAttribArray(vertexHandle);
    glDisableVertexAttribArray(normalHandle);
    glDisableVertexAttribArray(textureCoordHandle);
#endif

    QCAR::Renderer::getInstance().end();
}

And the last presentFrameBuffer (Objective-C++):

- (BOOL)presentFramebuffer
{
    BOOL success = FALSE;

    if (context) {
        [EAGLContext setCurrentContext:context];

#ifdef USE_OPENGL1
        glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer);
#else
        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
#endif

        success = [context presentRenderbuffer:GL_RENDERBUFFER];
    }

    return success;
}

Answer 1

It turned out that the projectionMatrix never was set.

I was missing the following calls:

// Cache the projection matrix:
const QCAR::CameraCalibration& cameraCalibration = QCAR::CameraDevice::getInstance().getCameraCalibration();
projectionMatrix = QCAR::Tool::getProjectionGL(cameraCalibration, 2.0f, 2500.0f);

They are originally placed in the startCameramethod in the ImageTarget sample from Vuforia.