OpenGL Interview Questions & Answers (2025)

• For drawing calls and state changes, OpenGL has lower CPU overhead than the other API's.
• There is more detailed documentation for OpenGL while other API's don't have such detailed documentation.
• OpenGL is more functional than any other API.
• OpenGL is portable.
• It is a cross-platform API, i.e. it can be used on various platforms such as- windows, WindowsMac, and some handheld devices.
• It is more extensible, i.e. new hardware features are exposed quickly.
• It has a stable interface until some bigger changes are made.

• Determine which square in the integer grid window has been occupied by the primitive.
• Assigning a color and depth value to each occupied grid.

It is a process in which the occupied pixels by the primitives are identified and the output variable of the vertex shader is interpolated for each covered pixel.

In vertex transformation, the vertices are transformed to their final clip space position in the vertex shader. The various major stages of vertex transformation are:

• Getting to the eye coordinates- the vertex provided to the GL is considered to be in the object space.
• Getting to clip coordinate- when the vertex is transformed by the projection matrix, then we get the clip matrix.
• Getting to normalized device coordinates- when each component is multiplied by 1/w, then we get the normalized device coordinates. It is mainly inside the clipping planes.
• Getting to window space- this is the final stage of the transformation pipeline. Everything out of the range is clipped away.

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