Built-in Uniforms

The following uniforms are available for all the passes, and are compatible with Shadertoy’s conventions:

vec3 iResolution
Viewport resolution (z is pixel aspect ratio, currently always set to 1.0).
int iFrame
Current frame index.
float iTime
Current time, in seconds.
float iTimeDelta
Time passed between the render start of the previous, and the current frame, in seconds.
float iFrameRate
Number of frames rendered per second.
vec4 iDate

x - Year

y - Month

z - Day

w - Time of day, in seconds.
vec4 iMouse

xy - Current mouse position (when Shader.Mouse input matches).

abs(zw) - Pressed mouse position.

z > 0.0 - Is mouse currently down (true for multiple frames).

w > 0.0 - Is mouse down started at the current frame (“pressed” event, true for a single frame).

Note that when mouse is down / pressed at x = 0 or y = 0, a small delta (0.0001) is added to z or w, in order to keep the checks above correct.
sampler2D iChannel#
Channel# sampler.
float[] iChannelTime
Channel time, in seconds (for .gif, or TextureSequence bindings).
float[] iChannelDuration
Channel duration, in seconds (for .gif, or TextureSequence bindings).
vec3[] iChannelResolution
Channel resolution.

Viewer Uniforms: The following uniforms are mostly needed for the Viewer Pass, but are also available for all the passes.

Output Uniforms / Variables

Fragment Shader

out vec4 FragColor# (where # is a number between 0 and 7): FragColor0 is set automatically to the mainImage output variable fragColor.

Compute Shader

writeonly image2D OutputTexture# (where # is a number between 0 and 7): Compute shader outputs can be set using imageStore (for example:
imageStore(OutputTexture0, texelCoord, vec4(1.0))).

By default only one texture is assigned, for additional textures the Pass Outputs property can be set.