OpenGL Computer Graphics 4

Question 1

What is a Vertex Array Object (VAO) in modern OpenGL?

Accepted Answer

An object that stores the state of vertex attribute bindings and buffer associations

Answer

A VAO records which VBOs are bound and how vertex attributes are laid out, so the entire state can be restored with a single glBindVertexArray() call.

Question 2

Which OpenGL draw call is most efficient when rendering many identical objects with different transforms?

Accepted Answer

glDrawArraysInstanced()

Answer

glDrawArraysInstanced() renders multiple instances in a single draw call, using gl_InstanceID in the shader to differentiate per-instance data.

Question 3

In Phong lighting, which component is independent of the viewer's position?

Accepted Answer

Ambient and diffuse

Answer

Ambient is a constant term and diffuse depends only on the light direction and surface normal, not the viewer position; specular does depend on the view vector.

Question 4

What does 'gl_FragCoord' represent in a GLSL fragment shader?

Accepted Answer

The window-space position (x, y, z, 1/w) of the fragment

Answer

gl_FragCoord holds the fragment's position in window space, where x and y are pixel coordinates and z is the depth value written to the depth buffer.

Question 5

What is the effect of setting the texture wrap mode to GL_CLAMP_TO_EDGE?

Accepted Answer

Texture coordinates outside [0,1] are clamped to the nearest edge texel

Answer

GL_CLAMP_TO_EDGE prevents texture bleeding by clamping coordinates to [0.5/N, 1-0.5/N], sampling only edge texels for out-of-range coordinates.

OpenGL Practice Test

OpenGL Practice Test

OpenGL Computer Graphics 4