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Geometry filter shaders

Geometry filter is another score-specific, ISF-derived shader format. It attaches a vertex transformation to incoming geometry for a downstream renderer. Unlike CSF, it does not ask you to dispatch a compute kernel; unlike raw raster, it does not require a complete vertex/fragment pipeline.

Use it to deform a mesh or change vertex attributes before display. Connect a geometry source to Geometry In, then Geometry Out to a compatible renderer such as Model display. The Animated Sphere Geometry Filter is a working example.

Header and source file

Use a .glsl file with a JSON comment header. MODE selects the geometry-filter format, and INPUTS defines controls using the ISF input vocabulary. For example:

/*{
  "ISFVSN": "2",
  "MODE": "GEOMETRY_FILTER",
  "DESCRIPTION": "Time-varying vertex displacement",
  "INPUTS": [
    { "NAME": "intensity", "TYPE": "float", "DEFAULT": 0.01, "MIN": 0.0, "MAX": 0.1 }
  ]
}*/

void process_vertex(inout vec3 position,
                    inout vec3 normal,
                    inout vec2 uv,
                    inout vec3 tangent,
                    inout vec4 color)
{
    position += this_filter.intensity * 10.0 * sin(TIME * position);
}

The body follows the deformation in the supplied sphere example. This is a callback, not a standalone main(): the renderer supplies the enclosing vertex shader. Keep the header and body together when saving a file or adding it to the user library.

Callback contract

Argument Type Purpose
position inout vec3 Vertex position to transform.
normal inout vec3 Surface normal used for shading.
uv inout vec2 Texture coordinates.
tangent inout vec3 Tangent attribute.
color inout vec4 Vertex color.

Arguments are mutable: leaving one unchanged preserves the value supplied to the callback. Displacing a position does not automatically give the corresponding deformed normal; update the normal as part of the transformation when the intended lighting requires it. The source mesh and renderer still determine which attributes are available and how they are used.

Access header controls through this_filter, as in this_filter.intensity. TIME is available for animation. Do not copy ISF fragment output code into this callback: it changes vertex attributes, not a pixel color attachment. Do not add the raw-raster main() prologue or epilogue around it; that enclosing shader belongs to the renderer.

For GLSL types and portable arithmetic, see the GLSL runtime reference. For explicit geometry buffers, generated topology or compute feedback, use the CSF geometry reference.

Implementation reference

The current Geometry filter process defines the callback and validates it inside a generated vertex shader. Its library handler identifies .glsl files with the GEOMETRY_FILTER mode. These host conventions are specific to score, not part of standard ISF.