OpenGL OpenGL MCQ 4

Question 1

Which OpenGL feature allows drawing multiple instances of a mesh with a single draw call?

Accepted Answer

Instanced rendering via glDrawArraysInstanced()

Answer

glDrawArraysInstanced() submits the geometry once and renders it a specified number of times, with gl_InstanceID available in the vertex shader to differentiate instances.

Question 2

What is the purpose of mipmaps in OpenGL texturing?

Accepted Answer

Provide pre-filtered smaller texture versions to reduce aliasing at distance

Answer

Mipmaps are pre-computed downscaled versions of a texture used when the textured surface is small on screen, reducing aliasing and improving performance.

Question 3

In GLSL, what does the 'varying' keyword (or 'in/out' in modern GLSL) represent?

Accepted Answer

Data interpolated across a primitive from vertex shader to fragment shader

Answer

Varying variables carry per-vertex data (like color or texture coordinates) that are automatically interpolated by the rasterizer before reaching fragment shaders.

Question 4

Which OpenGL query object type measures how long a GPU operation takes?

Accepted Answer

GL_TIME_ELAPSED

Answer

GL_TIME_ELAPSED query objects measure the number of nanoseconds elapsed on the GPU between glBeginQuery() and glEndQuery() calls.

Question 5

What does enabling GL_SCISSOR_TEST do in OpenGL?

Accepted Answer

Restricts rendering to a rectangular region of the framebuffer

Answer

The scissor test discards fragments outside the scissor rectangle defined by glScissor(), useful for UI clipping or partial screen updates.

OpenGL Practice Test

OpenGL Practice Test

OpenGL OpenGL MCQ 4