Forward and deferred rendering

Question 1

What is forward rendering?

Answer 1

Forward rendering is when lighting is computed while rendering geometry. All lights affecting an object are processed during its draw call.

Question 2

How does forward rendering handle multiple lights?

Answer 2

It renders objects multiple times - once for each light - in additive passes.

Question 3

What happens during the first pass of forward rendering?

Answer 3

The first pass writes depth and computes indirect lighting without blending.

Question 4

What happens during additional passes in forward rendering?

Answer 4

Later passes use additive blending (GL_ONE, GL_ONE), don’t write depth, and compute lighting for each light.

Question 5

What is deferred rendering?

Answer 5

Deferred rendering delays lighting calculations until after all geometry has been rendered. It separates geometry and lighting into two stages.

Question 6

What is the main advantage of deferred rendering over forward rendering?

Answer 6

It avoids re-rendering all objects for each light - improving performance when many lights are present.

Question 7

What are the two main passes in deferred rendering?

Answer 7

Geometry pass and lighting pass

Question 8

What happens during the geometry pass in deferred rendering?

Answer 8

All geometry is rendered into multiple textures (g-buffers), each storing different surface data (like depth, normals, albedo)

Question 9

What happens during the lighting pass in deferred rendering?

Answer 9

Lighting is computed by reading from the g-buffers. Each light is rendered in its own pass, often with light-shaped geometry.

Question 10

What is a G-buffer?

Answer 10

A G-buffer is a set of textures storing geometry data like positions, normals and material properties.

Question 11

What kind of data is typically stored in a G-buffer?

Answer 11

Common data include depth, surface colour (albedo), normals and material properties like reflectance.

Question 12

What are some examples of specific G-buffers used in Blinn-Phong lighting?

Answer 12

• Depth
• Albedo
• Normals
• Material properties

Question 13

What are some advantages of deferred rendering?

Answer 13

• Efficient with many lights
• Clean lighting seperation
• Easier to apply post-processing effects

Question 14

What are the main limitations of deferred rendering?

Answer 14

• High memory usage
• Complex shaders due to all lighting types
• Cannot handle transparency, since each fragment only stores one depth and one colour.