Deferred lighting

1. Inferred rendering
http://ozlael.egloos.com/

2. Forward Rendering
● Traditional Render
● Single Pass Lighting
● Multipass Lighting

3. Forward Rendering
:Single Pass Lighting
● For each object:
Render mesh, applying all lights in one shader
● Good for scenes with small numbers of li
ghts (eg.outdoor sunlight)
● Difficult to organize if there are many light
s
●
Shader combinations explosion

4. Forward Rendering
:Multipass Lighting
● For each light:
– For each object affected by the light:
● framebuffer += object * light
● Worst case complexity is num_objects * n
um_lights
● Shader for each material and light type

5. Forward Rendering
:Multipass Lighting
● Wasted shader cycles
– Invisible surfaces / overdraw
– Triangles outside light influence
● Ideally the scene should be split exactly a
long lightboundaries, but getting this right
for dynamic lightscan be a lot of CPU wor
k

6. Deferred Rendering
● For each object:
– Render to multiple targets
– Render surface properties into the G-Buffer
● For each light:
– Apply light as a 2D postprocess
– Use G-Buffer to compute lighting
– Add result to frame buffer

7. Deferred Rendering
● Worst case complexity is num_objects +
num_lights
● Simpler shaders

8. Deferred Rendering
G-buffer

9. Deferred Rendering
G-buffer

10. Deferred Rendering
G-buffer

11. Deferred Rendering
Result

12. MRT

13. Determine Lit Pixels

14. Determine Lit Pixels

15. Early-Z Pass
● Similar to Early-Z Pass
– 1st Pass: Visibility tests
– 2nd Pass: Shading
● Different than Early-Z Pass
– Geometry is only transformed once

16. Deferred Rendering
Weak point
● Does not handle transparent objects
– Forward Rendering Pass
● H/W Anti-aliasing difficult
● Material limited
● Many memory bandwidth

17. Pre-light Pass
● Geometry pass:
– fill up normal and depth buffer
● Lighting pass:
– store light properties in light buffer
● 2. Geometry pass:
– fetch light buffer and apply different material
terms per surface by re-constructing the
lighting equation

18. Pre-light Pass
● Geometry pass:
– fill up normal and depth buffer
● Lighting pass:
– store light properties in light buffer
● 2. Geometry pass:
– fetch light buffer and apply different material
terms per surface by re-constructing the
lighting equation

19. Pre-light Pass
Render opaque Geometry sorted front-to-back
Normals
Depth Color
Specular Power
Blit Lights into Light Buffer (sorted front-to-back)
Light Buffer
Render opaque Geometry sorted front-to-back
or
Blit ambient term and other lighting terms into final image
Frame Buffer

20. Pre-light Pass
Resistance 2TM in-game screenshot; first row on the left is the depth buffer, on the right is the normal buffer; in the second row is the diffuse light buffer
and on the right is the specular light buffer; in the last row is the final result.

21. Pre-light Pass
● Flexible Materials
● H/W MSAA
● Not Lighting/Shadowing Alpha Geometry