Ed2 Week 2

Front 1

What is Forward Rendering?

Back 1

Forward Rendering, also known as Direct Rendering, will render out final pixel colors

Front 2

Benefits and drawbacks of Forward Rendering?

Back 2

Benefit:
-- Geometry is typically transformed only once

Drawbacks:
--Hardware limit on number of lights (main reason)
--Complex shaders due to differing types of materials and effects
--Shadow Maps of all lights must be loaded
--High cost overdraw

Front 3

What is Multi-pass Forward Rendering?

Back 3

-->For each light in the scene
-->For each mesh in range of the light
-->Render mesh with just current light applied
-->Additive blending will combine results of final
image

Front 4

Benefits of Multi-Pass Forward Rendering?

Back 4

--No hard limit on the number of lights since each light is rendered separately
--Shaders can be simpler since we will have one shader for each type of light
--Can/should/possibly is easier to cull lights since if geometry being rendered is not in the bound of the current light, don't render

Front 5

Drawbacks of Multi-Pass Forward Rendering?

Back 5

Repeated Rendering work
--Vertex shaders for rendered geometry has to
run for each light.
--Texture filtering work may be repeated
--Possible increase in cache misses

Worst case number of render passes
--NumberOfObjects * NumberOfLights

High cost for overdraw
--A pixel can be rendered multiple times

Increased context switching
--We either render all objects for each light, preventing us from rendering similar objects together, or we process each light for each object causing us to switch shaders and light parameters repeatedly

Front 6

What is Deferred Shading?

Back 6

Broken into 2 stages, the geometry stage and the lighting stage.

Needs: depths, diffuse color, normal color & specular material

Front 7

Benefits of Deferred Shading?

Back 7

--No hard limit on number of lights
--Reduced cost of overdraw
--overdraw will only happen during geometry
stage, which is a relatively cheap stage
compared to lighting
--Simplified shaders
--Geometry is typically transformed only once
--Worst case number of passes = number object + number of lights

Front 8

Drawbacks of Deferred Shading?

Back 8

--Memory footprint
--Precision loss
--how to pack an XYZ value where each component
is a 32 bit float into one 32 bit location?
--Additional data packing and unpacking costs
--Multi-sample anti-aliasing not well supported
--Transparency does not work in deferred

Front 9

How do we pick if the Z-axis of the Deferred Shader should be positive or negative?

Back 9

Move all the lighting to happen in view space as though the camera was the origin. A negative Z would then represent a backface, which we would not be rendering

Front 10

What are the three reasons we do not use Object Space Maps?

Back 10

1. They cannot reuse texture space
2. They cannot support texture mirroring
3. Poor support for deformable geometry

Front 11

What is the difference between a Bump map and a Normal map?

Back 11

Bump maps use a height map to define surface properties, while normal maps use the normals of the object.

Front 12

In Tangent Space, where is the origin located in relation to an object?

Back 12

In Tangent Space, the origin is oriented with a specific surface on the object.

Front 13

In regards to Tangent Space, what is a TBN matrix?

Back 13

The TBN matrix is a 3x3 matrix that stores a Tangent, Bitangent, and Normal. The Tangent and Bitangent are vectors that are perpendicular to themselves, and to the Normal.

Front 14

How do we calculate our TBN matrix?

Back 14

- Transform our input normal by our world matrix and store in TBN[2].
- Transform our input tangent by our world matrix and store in TBN[0].
- Cross our new normal and tangent to create out bitangent, store in TBN[1].

Front 15

What is Ambient Occlusion Mapping?

Back 15

It is a technique that provides a texture map that more accurately represents how bouncing rays of lights will likely hit a certain location.