OpenGL OpenGL Rendering Pipeline 2

Question 1

What is the purpose of the depth test in OpenGL?

Accepted Answer

Ensures fragments closer to the camera overwrite farther ones

Answer

The depth test compares each fragment's z value against the depth buffer, keeping only the closest fragment per pixel.

Question 2

What does glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) do?

Accepted Answer

Resets the color and depth buffers to their clear values before rendering a new frame

Answer

glClear with those flags fills the color buffer with the clear color and the depth buffer with 1.0 (far), preparing for the next frame.

Question 3

What OpenGL blending equation produces standard over-compositing for transparent objects?

Accepted Answer

GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA

Answer

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) blends source and destination by the fragment's alpha, the standard transparency blend.

Question 4

Which OpenGL feature limits rendering to a rectangular sub-region of the framebuffer?

Accepted Answer

glScissor

Answer

glScissor(x, y, width, height) with GL_SCISSOR_TEST enabled discards all fragments outside the defined rectangle.

Question 5

What OpenGL function swaps the front and back buffers to display the completed frame?

Accepted Answer

SwapBuffers (platform API)

Answer

Buffer swapping is a platform-level operation (e.g., SDL_GL_SwapWindow or SwapBuffers on Windows) not an OpenGL core function.

OpenGL Practice Test