shader_transparent_chicago

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The transparent chicago shader is applied to surfaces that require transparent elements. This shader can contain up to 4 "stages" of bitmaps, where each stage and its alpha can animate and blend to form final accumulated diffuse and alpha channels. The shader can be given a final framebuffer blending function too, like add for holograms.

Alpha-tested BSP surfaces like 2D billboard trees and ladders can use the simpler shader_environment instead.

If referenced as an extra shader layer, this tag will inherit some fields from its parent regardless of its own flags (e.g. first map type).

	Function/global	Type
	`(rasterizer_active_camouflage_multipass [boolean])` Toggles whether or not transparent shaders are shown through active camouflage. If disabled, shaders like glass or lights will not be visible through a camouflaged unit.	Global
	`(rasterizer_model_transparents [boolean])` Toggles the rendering of transparent shaders in models. For example, the Warthog's windshield.	Global
	`(<void> reload_shader_transparent_chicago)` Reloads all shader_transparent_chicago tags. Use this in Sapien or Standalone to see changes to their bitmaps or parameters without having to reload the scenario.	Function

Function/global

Type

(rasterizer_active_camouflage_multipass [boolean])

Toggles whether or not transparent shaders are shown through active camouflage. If disabled, shaders like glass or lights will not be visible through a camouflaged unit.

Global

(rasterizer_model_transparents [boolean])

Toggles the rendering of transparent shaders in models. For example, the Warthog's windshield.

Global

(<void> reload_shader_transparent_chicago)

Reloads all shader_transparent_chicago tags. Use this in Sapien or Standalone to see changes to their bitmaps or parameters without having to reload the scenario.

Function

Structure and fields

Field Type Comments

numeric counter limit uint8

shader transparent chicago flags bitfield

Flag	Mask	Comments
alpha tested	`0x1`
decal	`0x2`
two sided	`0x4`
first map is in screenspace	`0x8`
draw before water	`0x10`
ignore effect	`0x20`
scale first map with distance	`0x40`
numeric	`0x80`

first map type enum

Option	Value	Comments
2d map	`0x0`
first map is reflection cube map	`0x1`
first map is object centered cube map	`0x2`
first map is viewer centered cube map	`0x3`

framebuffer blend function enum

Option	Value	Comments
alpha blend	`0x0`
multiply	`0x1`
double multiply	`0x2`
add	`0x3`
subtract	`0x4`
component min	`0x5`
component max	`0x6`
alpha multiply add	`0x7`

framebuffer fade mode enum

Option	Value	Comments
none	`0x0`
fade when perpendicular	`0x1`
fade when parallel	`0x2`

framebuffer fade source enum

Option	Value	Comments
none	`0x0`
a out	`0x1`
b out	`0x2`
c out	`0x3`
d out	`0x4`

lens flare spacing float

lens flare TagDependency: lens_flare

extra layers

Block

HEK max count: 4

Specifies additional shaders to render before this parent shader. The same geometry is essentially rendered multiple times with different shaders. Each extra layer shader can have an independent framebuffer blend function, but some settings like first map is reflection cube map from the parent will also override the setting in extra layers. Although any shader type can be referenced here, only the chicago transparent shaders are properly supported; the other types will either not render or render incorrectly. Warning: Using a shader with extra layers on an object with transparent self occlusion enabled may cause Sapien and Standalone to crash if there are too many overlapping faces from the viewing angle.

Field	Type	Comments
shader	`TagDependency`: shader

maps

Block

HEK max count: 4
Max: 4

Warning: HEK Sapien will crash if this block is empty. The shader is not rendered in H1A Sapien or in-game in this case.

Field Type Comments

flags bitfield

Flag	Mask	Comments
unfiltered	`0x1`
alpha replicate	`0x2`
u clamped	`0x4`	Texture coordinates outside the U 0-1 range will be clamped to the edges. See u animation function for caveats.
v clamped	`0x8`	Texture coordinates outside the V 0-1 range will be clamped to the edges. See u animation function for caveats.

color function enum

Option	Value	Comments
current	`0x0`
next map	`0x1`
multiply	`0x2`
double multiply	`0x3`
add	`0x4`
add signed current	`0x5`
add signed next map	`0x6`
subtract current	`0x7`
subtract next map	`0x8`
blend current alpha	`0x9`
blend current alpha inverse	`0xA`
blend next map alpha	`0xB`
blend next map alpha inverse	`0xC`

alpha function enum^?

map u scale float

map v scale float

map u offset float

map v offset float

map rotation float

mipmap bias

float

Min: 0
Max: 1

map TagDependency: bitmap

u animation source enum^?

u animation function

enum

Default: one

Horizontal animation function. The u and v animation functions default to 1, which results in effectively an additional map u offset and map v offset of 1. This causes some counterintuitive side effects. The u clamped and v clamped flags will not work properly, stretching the corner pixel across the entire canvas The rotation animation functions will behave unexpectedly as well, with 1 added to the rotation animation center coordinates. It is recommended to set the function to 0 if these features are being used.

Option	Value	Comments
one	`0x0`
zero	`0x1`
cosine	`0x2`
cosine variable period	`0x3`
diagonal wave	`0x4`
diagonal wave variable period	`0x5`
slide	`0x6`
slide variable period	`0x7`
noise	`0x8`
jitter	`0x9`
wander	`0xA`
spark	`0xB`

u animation period

float

Unit: seconds
Default: 1

u animation phase float

u animation scale

float

Unit: world units
Default: 1

v animation source enum^?

v animation function

enum^?

Default: one

Vertical animation function. See u animation function for caveats.

v animation period

float

Unit: seconds
Default: 1

v animation phase float

v animation scale

float

Unit: world units
Default: 1

rotation animation source enum^?

rotation animation function enum^?

rotation animation period

float

Unit: seconds
Default: 1

rotation animation phase float

rotation animation scale

float

Unit: degrees
Default: 360

rotation animation center

Point2D

Coordinates for the center of map rotation. Note that these coordinates may be offset unintuitively if u animation function and v animation function are not zero.

Field	Type	Comments
x	`float`
y	`float`

extra flags bitfield

Flag	Mask	Comments
don't fade active camouflage	`0x1`
numeric countdown timer	`0x2`
custom edition blending	`0x4`	Custom edition originally had an incorrect implementation of the multiply and double multiply framebuffer blend functions for transparent shaders which made fully dark pixels transparent. MCC is fixed but this flag allows modders to use custom edition's blending, which can help when porting legacy tags to the updated engine.

Acknowledgements

Thanks to the following individuals for their research or contributions to this topic:

Galap (Rotation coordinate offset writeup)
Kavawuvi (Invader tag definitions)
MosesOfEgypt (Research on tag structure research, extra layers crash, rotation coordinate offset)

shader_transparent_chicago

Related HaloScript

Structure and fields

Acknowledgements