Rainfall environment#

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Rainfall injects custom HLSL into generated GameCube TEV shaders at runtime. This section covers symbols you see most in fragment mods (prev, input.position, u_time). Vertex mods use model-space locals and state uniforms, see Custom shader mods.

Environment uniforms#

The shader code has access to variables defined in the FSUniforms cbuffer:

u_time (float)#

• Meaning: seconds since the game started.
• Purpose: drive animations, waves, and oscillations.

  // One full pulse cycle every 1.0s
  float pulse = sin(u_time * 6.283185f); // 2 * pi * u_time
  

_timePad.x (float)#

• Meaning: 1.0 / renderWidth
• Purpose: turn pixel x into a 0–1 UV coordinate.

_timePad.y (float)#

• Meaning: 1.0 / renderHeight
• Purpose: turn pixel y into a 0–1 UV coordinate.

  float2 uv = input.position.xy * float2(_timePad.x, _timePad.y);
  

Global fragment registers#

• prev (float4)
  • Meaning: pixel color from the normal render pipeline before your mod runs (RGBA).
  • Use: tint, grade, or post-process the final color.

    prev.rgb *= float3(0.9f, 1.1f, 0.9f);
    

Screen variables#

• input.position.xy (float2)
  • Meaning: pixel coordinates from (0, 0) at the top-left to (width, height).
  • Use: screen-space grids, scanlines, and similar effects.

    if (int(input.position.x) % 3 == 0) {
        prev.rgb *= 0.8f;
    }
    

• input.position.z (float)
  • Meaning: non-linear depth in [0.0, 1.0].
  • Use: avoid this for distance-based effects, and prefer input.position.w for linear depth.
• input.position.w (float)
  • Meaning: 1.0 / w_clip (reciprocal clip-space depth).
  • Linear depth: camera distance in world units:

    float eyeDepth = 1.0f / input.position.w;
    

  • 2D / HUD guard: HUD, text, and ortho draws use w_clip = 1.0, so they read as input.position.w == 1.0f:

    bool is3D = input.position.w != 1.0f;
    if (is3D) {
        // Apply 3D shader mod here
    }