Unable to Render After Successfully Loading Volume

[TouKaienn]

Thanks for your amazing implementation.

I tried to run the code. However, I encountered an issue: the rendering result is always empty even after successfully loading the volume.
The terminal output:

The GUI output:

I found that this issue may be caused by this line;, the dir_world may output [0,0,0] and initialized ray direction may be [nan,nan,nan], which result in wrong rendering results.

I would greatly appreciate any guidance or suggestions to resolve this issue. Thank you for your time in advance!

[yuehaowang]

Hi,

Thanks for your questions!

This is a project I did many years ago. The last time I tried running it was nearly a year ago, and I didn't find any problems. So, before I can reproduce this issue, I may need to know your Linux distro, OpenGL & CUDA versions.

Also, could you help me check the line you mentioned, like printing the values of dir_world? It is not straightforward for me to see the reason why dir_world will become all zeros.

[TouKaienn]

Many Thanks for your prompt response.

Here is more information about my environment:
Linux distro: Ubuntu 22.04
OpenGL version: 4.6.0 Nvidia 550.120
CUDA version: 11.8

The package versions do not exactly match the test environment in readme. Maybe I should try to downgrade opengl or cuda version in this case.

I print out the values of dir_world by modifying the line I mentioned into:

__host__ __device__ Ray Camera::generateRay(float dx, float dy) const
{
    float half_fov = vertical_fov / 2;
    float image_aspect_ratio = film.getAspectRatio(); 
    float im_plane_w = tan(half_fov * PI / 180) * image_aspect_ratio;
    float im_plane_h = tan(half_fov * PI / 180);
    
    float x_cam = (2 * (dx / film.resolution.x()) - 1) * im_plane_w;
    float y_cam = (2 * (dy / film.resolution.y()) - 1) * im_plane_h;
    Eigen::Vector3f dir_camera(x_cam, y_cam, -1.0);

    Eigen::Matrix3f view;
    view.col(0) << right;
    view.col(1) << up;
    view.col(2) << forward;
    Eigen::Vector3f dir_world = (view * dir_camera).normalized();
    // print out all dir_world
    printf("dir_world: %f %f %f\n", dir_world.x(), dir_world.y(), dir_world.z());
    
    
    return Ray(position, dir_world);
}

The terminal output is:

Thanks again for your help.

[TouKaienn]

Hi,

I figured out how to solve this problem by calculating dir_world manually each time. In other words, I modified the line I mentioned above into:

__host__ __device__ Ray Camera::generateRay(float dx, float dy) const
{
    float half_fov = vertical_fov / 2;
    float image_aspect_ratio = film.getAspectRatio(); 
    float im_plane_w = tan(half_fov * PI / 180) * image_aspect_ratio;
    float im_plane_h = tan(half_fov * PI / 180);
    
    float x_cam = (2 * (dx / film.resolution.x()) - 1) * im_plane_w;
    float y_cam = (2 * (dy / film.resolution.y()) - 1) * im_plane_h;
    Eigen::Vector3f dir_camera(x_cam, y_cam, -1.0);

    Eigen::Matrix3f view;
    view.col(0) << right;
    view.col(1) << up;
    view.col(2) << forward;

    //original
    // Eigen::Vector3f dir_world = (view * dir_camera).normalized(); 

   //new
    float dir_world_x = view(0,0) * dir_camera.x() + view(0,1) * dir_camera.y() + view(0,2) * dir_camera.z();
    float dir_world_y = view(1,0) * dir_camera.x() + view(1,1) * dir_camera.y() + view(1,2) * dir_camera.z();
    float dir_world_z = view(2,0) * dir_camera.x() + view(2,1) * dir_camera.y() + view(2,2) * dir_camera.z();
    Eigen::Vector3f dir_world(dir_world_x,dir_world_y,dir_world_z);    

    return Ray(position, dir_world);
}

And the dir_world can be calculated correctly and the rendering result is correct.

However, I still have no idea why the computation of Eigen::Vector3f dir_world = (view * dir_camera).normalized(); can not perform correctly in this case.

You may close this issue if you wish.

[yuehaowang]

Great to know you've resolved this issue. Probably it is due to the incompatibility of Eigen and the latest Ubuntu / CUDA.
I will look into this issue if I can later find a PC with a similar environment.