I received a call from HR two weeks after applying.

I was then given an online programming test, and after clearing it, I had a three-hour onsite interview.

The interview consisted of three technical rounds and one managerial round, with each interviewer taking 40-60 minutes.

Technical interview topics included:

• Linked lists
• Bit manipulation
• 3D graphics
• C/C++
• OS and device driver concepts

The manager asked some behavioral questions and puzzles.

Consider the following 3D scene representing an old town's main square:

• A single statue
  • static geometry, high polygon count
  • low complexity fragment shader
• A particle system simulating smoke
  • animated, rendered as a large set of points
• A small set of characters
  • animated geometry, medium polygon count
  • medium complexity fragment shader
• A large set of buildings
  • static geometry, low polygon count
  • low complexity fragment shader
• A background image/skybox
• The camera/viewpoint is continuously moving within the scene.

How would you render the statue – by itself – using OpenGL to achieve maximum vertex performance (vertices/second)?

How would you render the particle system – by itself – using OpenGL to achieve maximum vertex performance (vertices/second)?

How would you render the scene – as a whole – most efficiently on a GPU using OpenGL?

Given that the 3D scene was being rendered correctly but that you wanted to improve the performance further, how would you determine if the main performance limitation/bottleneck was located in the application, in the vertex processing stage, or in the fragment processing stage?