OpenGL OpenGL Shaders 3

Question 1

In GLSL, what is the data type of a 2D texture sampler?

Accepted Answer

sampler2D

Answer

sampler2D is the GLSL opaque type for binding a 2D texture to a fragment or vertex shader.

Question 2

What does the GLSL discard statement do in a fragment shader?

Accepted Answer

Prevents the fragment from being written to the framebuffer

Answer

discard terminates the fragment shader and drops the fragment so it does not update the framebuffer.

Question 3

Which GLSL built-in provides the window-space position of the current fragment?

Accepted Answer

gl_FragCoord

Answer

gl_FragCoord is a read-only built-in containing the (x, y, z, 1/w) window-space coordinates of the fragment.

Question 4

What OpenGL function retrieves the location of a uniform variable in a linked shader program?

Accepted Answer

glGetUniformLocation

Answer

glGetUniformLocation(program, name) returns the integer location index used to set that uniform's value.

Question 5

Which shader stage runs once per primitive and can modify or generate vertices between the vertex and fragment stages?

Accepted Answer

Geometry shader

Answer

The geometry shader receives a complete primitive and can emit zero or more new primitives to the rasterizer.

OpenGL Practice Test