triangle_vertex_count()

constexpr uint32_t MayaFlux::Portal::Graphics::triangle_vertex_count ( PrimitiveTopology  topology, uint32_t  n  )

constexprnoexcept

Vertices a span of n at topology yields once reduced to a TRIANGLE_LIST, with points becoming quads and line segments ribbons.

Closed form, so a caller can size a destination or budget a dispatch without inspecting vertex data. Spans too short to assemble a primitive yield zero rather than underflowing, and list topologies floor to whole primitives, so an odd LINE_LIST count drops its dangling vertex instead of reading past the span.

Definition at line 417 of file GraphicsUtils.hpp.

{
    switch (topology) {
    case PrimitiveTopology::POINT_LIST:
        return 6U * n;
    case PrimitiveTopology::LINE_LIST:
        return 6U * (n / 2U);
    case PrimitiveTopology::LINE_STRIP:
        return n < 2U ? 0U : 6U * (n - 1U);
    case PrimitiveTopology::TRIANGLE_LIST:
        return 3U * (n / 3U);
    case PrimitiveTopology::TRIANGLE_STRIP:
    case PrimitiveTopology::TRIANGLE_FAN:
        return n < 3U ? 0U : 3U * (n - 2U);
    }
    return 0U;
}

References LINE_LIST, LINE_STRIP, POINT_LIST, TRIANGLE_FAN, TRIANGLE_LIST, and TRIANGLE_STRIP.

Referenced by MayaFlux::Portal::Graphics::PrimitiveMill::milled_vertex_count().

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