GAM532DPS932 – Week 7Introduction to shadows

Shadow Effects

Light Light

Surface

Surface

No Shadows Shadows

Types of Shadow Techniques

Baked Lighting Blob Shadows Shadows Volumes Depth Map Shadows

Performant

Immersive

Baked Lighting and Static Lights

Lights and actors cannot move

Static lights are not part of the scene

Computations happen during development

Almost costless

Cannot change at runtime

Can be very high detail

Blob Shadows

Scene without shadow

Scene with blob applied to underlying

geometry

Static Shadow Texture

Light Dir:[ 0, -1, 0 ]

Light Dir:[ 0.7, -0.7, 0 ]

Shadows can move with the sceneLow performance cost

Shadows cannot change at runtimeLow detail approximations

Only works well with single simple light

Shadows Volumes

Extrude Shadow Volume

Render Scene Depth Render Volume Stencil

Shadowed Scene

Extruding Shadow Volumes

Shadowed Scene

Light

Actor

Shadow Volumes

Rendering Depth and Stencil

Render Depth Render Volume Stencil

AFront Face: Fail (-

1)Back Face: Fail

(+1)Stencil = 0B

Front Face: Pass (0)

Back Face: Fail (+1)

Stencil = 1CFront Face: Pass

(0)Back Face: Pass (0)

Stencil = 0

Final Result

Additive

Blocks the light for each light pass

Modulative

Darkens the geometry after lighting pass

CPU Intensive

Modulative darkens scene with multiple lights

Self Shadowing

Dynamically changing Shadow

Detail limited by mesh detail

High Detail (model limited)

Very expensive with high polygon meshs

Depth Texture Shadows

Render scene depth from each light

Render Scene from main camera for

each light

Compare depth from light’s depth target to each

fragment

Render from Shadow Camera

Render scene depth from each light

Bind each shadow camera to a depth target (no color

needed)

struct Light { float3 position; float4 diffuse; float4 specular; float3 attenuation; float3 spot;};

Texture2D shadowTex : register(t0);SamplerState shadowSamp : register(s0);

Bind each depth target to a slot in the

shader

Render from Main Camera

Render scene from the main camera

Project the fragment position into the light’s space, using modified x,y

for uv texcoords

Compare depth stored in texture vs

projected distance from the light

Final Result

Translucency effects easily added

Expensive (re-render scene for each light)

Self Shadowing

Dynamically changing Shadow

Detail limited by texture size

High Detail (texture limited)

Point lights are very expensive to cast shadows from (6 renders per light)

Some Advanced Stuff

Texture resolution can cause aliasing

Sampling adjacent texels and blending can soften shadows

Sampling many adjacent texels and

applying noise algorith

When to Use Each Technique

Baked Lighting Blob Shadows Shadows Volumes Depth Map Shadows

Areas where lighting and geometry won’t

change[ceiling of a tall building]

Objects that are too far away to need detail, but close enough

to need shadows[distant trees,

buildings]

When you need to cast from point lights or when depth maps are too expensive

[Small light points, candles]

Areas that need high quality

shadows from directional or spot lights[light from a

window]

To Do• Begin work on your enhancement• Begin work on OpenGL labs• Update wiki with all team related information• Prepare for Mid-term (read study guide)