Function macroTaps

Defines the samples of textures per-pass, as GLSL preprocessor macros.

The macros define the minimal sampling of textures for the data the active pass's values derive from; creates a data list containing the samples; the samples list variable names are required as created by macroSamples.

Handles sampling states in a flat array of textures, or merged in one texture (in both sampler2D, and sampler3D/sampler2DArray where supported). Merging allows shaders to access past steps by non-constant lookups; e.g: attributes cause sampler array index must be a literal expression on GLSL3 spec and other platforms (e.g: D3D); note these need texture repeat wrapping.

They're set up as function-like macros that may be called from the shader to initialise the mappings arrays with a given name. Caches the result if macros generation is enabled, to help reuse shaders.

See

• sampler array index must be a literal expression
• sampler2DArray
• sampler3D
• macroSamples
• hasMacros
• getGLSLList
• maps.mapStep
• data.toData
• inputs.toUniforms
• cacheDef

Example: ```javascript const values = [2, 4, 1]; const derives = [2, , [[1, 0], true]]; const maps = { values, derives, channelsMax: 4 }; // No optimisations - values not packed, single texture output per pass. const state = { pre: '', maps: mapStep({ ...maps, buffersMax: 1, packed: 0 }) }; // Uses the first pass by default. macroTaps(state); // => '@todo'; // Next pass in this step - no derives, no samples nor reads. state.passNow = 1; macroTaps(state); // => ''; // Next pass in this step. ++state.passNow; macroTaps(state); // => '@todo'; // Automatically packed values - values across fewer textures/passes. // Can bind more texture outputs per pass - values across fewer passes. // Also fewer samples where values share derives or textures. state.maps = mapGroups({ ...maps, buffersMax: 4 }); state.passNow = 0; macroTaps(state); // => '@todo'; ```