Camera HFOV always returns same value even if it changed

[chapulina]

Environment

• OS Version: Ubuntu Focal
• Source or binary build? Source, ign-rendering6
• If this is a GUI or sensor rendering bug, describe your GPU and rendering system. Otherwise delete this section.
  • Rendering plugin: Both ogre and ogre2

Description

• Expected behavior: Camera::HFOV returns the current angle
• Actual behavior: Always returns the initial angle

Steps to reproduce

On a Gazebo or GUI plugin, print the camera's HFOV at every frame. The number is constant.

However, looking at the 3D view, it looks like the HFOV varies a lot when the image size changes, but the VFOV remains about the same:

Additional info

I believe what happens is that ign-rendering's API exposes HFOV, but Ogre uses VFOV. So when the user sets HFOV, we store it, then calculate VFOV to pass to Ogre:

https://github.com/ignitionrobotics/ign-rendering/blob/ae292a88bd752822e0c0f6ed6fd6029e3fc64d0e/ogre2/src/Ogre2Camera.cc#L75-L81

Then when the image size changes, Ogre keeps the VFOV fixed and changes the HFOV to compensate, but our API doesn't pick that up.

I think that a solution would be to override Camera::HFOV and return the current angle calculated from VFOV. I haven't opened a PR because I wanted to check that all my assumptions are correct and I'm not missing some important detail.

[iche033]

yeah I think that's what's happening. Alternatively, we can try to maintain the HFOV by calculating the new VFOV based on the new aspect ratio whenever window size changes. Either way works.

[chapulina]

Alternatively, we can try to maintain the HFOV by calculating the new VFOV based on the new aspect ratio whenever window size changes.

I thought of that, but I assumed that the current behaviour was preferred because I feel like most simulations are spread horizontally rather than vertically.

I'll look into fixing the returned value.

[azeey]

Fixed by #636