LightStorage

The render pipeline stores all lights and shadow sources into buffers on the GPU. This page describes the data layout used for storing the data into those buffers.

This data is stored in a texture buffer, one for the lights and one for the shadow source. The format of those buffers is RGBA32F, so the data is grouped in block of 4 floating point components (Thats what .x, .y, .z and .w refer to).

The data offset (written as +N, e.g. +5), determines the offset of the given value. An offset of +3 means that the data is stored as the fourth float after the base offset (equal to V0.w).

Light Storage

Each Light is stored in the LightBuffer with 4 vec4's = 16 floats

The data layout is:

[V0.x] +0: Light Type
[V0.y] +1: IES Profile Index (or -1 for no profile)
[V0.z] +2: First Shadow Source index (or -1 for no shadows)
[V0.w] +3: Max culling radius    
[V1.x] +4: Position.x
[V1.y] +5: Position.y
[V1.z] +6: Position.z
[V1.w] +7: Color.r
[V2.x] +8: Color.g
[V2.y] +9: Color.b
       +10-15: [Any additional properties depending on the light type]

NullLights

Null lights have a light type of 0, to indicate there is no light at that slot. They don't have any additional properties, too.

Sphere Lights

       +0-9: [see above]
[V2.z] +10: Sphere Radius
       +11-15: [unused]

Spot Lights

       +0-8: [see above]
[V2.z] +10:  Field of View
[V2.w] +11:  Direction.x
[V3.x] +12:  Direction.y
[V3.y] +13:  Direction.z
       +14-15: [unused]

Rectangle Lights

       +0-8: [see above]
[V2.z] +10:  Up Vector.x
[V2.w] +11:  Up Vector.y
[V3.x] +12:  Up Vector.z
[V3.y] +13:  Right Vector.x
[V3.z] +14:  Right Vector.y
[V3.w] +15:  Right Vector.z

Tube Lights

       +0-8: [see above]
[V2.z] +10:  Tube radius
[V2.w] +11:  Tube length
[V3.x] +12:  Direction.x
[V3.y] +13:  Direction.y
[V3.z] +14:  Direction.z
       +15: [unused]

Shadow Source Storage

Each Shadow source is stored in the SourceBuffer with 5 vec4's = 20 floats

The data layout is:

[V0.x - V3.w] +0-16: View-Projection Matrix
[V4.x] +17: uv-coordinate x
[V4.y] +18: uv-coordinate y
[V4.z] +19: uv-coordinate width
[V4.w] +20: uv-coordinate height

GPU Commands:

Commands have the layout:

+0:    [Command ID]
+1-31: [Command Data]

There are several command types:

CMD_INVALID

Does nothing, gets just skipped

CMD_STORE_LIGHT

Stores a new light into the light data, command layout:

+0:    [Command ID]
+1:    [Light ID]
+2-31: [Light Data, see above]

The light id is used to figure where to write the light into the global lights storage buffer. This command basically just takes the Light Data, and writes it to the specified location.

CMD_REMOVE_LIGHT

This command just sets all of the light data to zeroes, so that the light gets a NullLight, and ignored.

+0     [Command ID]
+1:    [Light ID]
+2-31: [unused]

CMD_STORE_SOURCE

Stores a new shadow source into the shadow source data, command layout:

+0:    [Command ID]
+1:    [Light ID]
+2-31: [Source Data, see above]

CMD_REMOVE_SOURCE

This command sets all of the source data to zeroes, to indicate its not further used.

+0:    [Command ID]
+1:    [Source ID]
+2-31: [unused]