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Numeric Expression Node (ExprTk)

A single, expression-driven math node replaces the legacy fixed-op math primitives. Implemented in Rendering/MathExpression.{h,cpp} (PCH disabled on the .cpp so the heavy ExprTk template instantiations don't leak into the rest of the engine TU).

  • Dynamic inputs: starts with one input A. Use the ➕ Add Input button in the Properties panel to add B, C, … up to Z (26-input cap). Each row has an ✕ button to remove just that input.
  • Expression: a TextBox at the top of the Properties panel holds the formula. Examples:
    • A + B * C
    • max(A, B, C)
    • if (A > B, A, B)
    • sin(A) * 0.5 + 0.5
    • pow(clamp(A, 0, 1), 2.2)
  • Canvas display: the formula is rendered under the node title as = <expression> so it's readable at a glance in the graph.
  • Output: a single float analysis field named Result, available on the orange data pin and bindable to any downstream scalar property.
  • Errors: parse / evaluation errors surface in the per-node log pane (node_logs MCP tool). The node short-circuits to 0.0 until the expression compiles cleanly.
  • Persistence: the expression and the live input list both round-trip through graph JSON.

ExprTk feature flags. Rendering/MathExpression.cpp defines exprtk_disable_string_capabilities, exprtk_disable_rtl_io, exprtk_disable_rtl_io_file, exprtk_disable_rtl_vecops, exprtk_disable_enhanced_features, and exprtk_disable_caseinsensitivity before #include-ing exprtk.hpp. This trims the library to its math-only core; without these flags the MSVC Release optimizer was producing a 0xC0000005 in the regex / IO subsystems on first evaluation. Only finite scalar expressions are supported — no strings, files, or vector return values.

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