as_point_vertex_access()

MAYAFLUX_API std::optional< VertexAccess > MayaFlux::Kakshya::as_point_vertex_access	(	std::span< const DataVariant >	channels,
		const VertexAccessConfig &	config = {}
	)

Assemble point-vertex-compatible bytes from one or more data channels.

channels[0] must supply position data (vec3 or uint8_t interleaved). channels[1..5] optionally supply color, scalar, uv, normal, tangent in canonical field order. Missing trailing channels are filled from config. A single uint8_t channel of N*60 bytes is passed through zero-copy.

Parameters

channels	Source channels in canonical field order.
config	Default attribute values for absent channels.

Returns

Populated VertexAccess, or std::nullopt on empty or incompatible input.

Definition at line 89 of file VertexAccess.cpp.

{
    if (channels.empty()) {
        MF_ERROR(Journal::Component::Kakshya, Journal::Context::Runtime,
            "as_point_vertex_access: no channels supplied");
        return std::nullopt;
    }
 
    // Zero-copy path: single uint8_t channel of N*60 bytes is already interleaved.
    if (channels.size() == 1) {
        if (const auto* b = std::get_if<std::vector<uint8_t>>(&channels[0])) {
            if (b->size() % 60 != 0) {
                MF_ERROR(Journal::Component::Kakshya, Journal::Context::Runtime,
                    "as_point_vertex_access: uint8_t byte count {} not a multiple of 60",
                    b->size());
                return std::nullopt;
            }
            const auto count = static_cast<uint32_t>(b->size() / 60);
            auto layout = VertexLayout::for_points();
            layout.vertex_count = count;
            return VertexAccess { .data_ptr = b->data(), .byte_count = b->size(), .layout = layout };
        }
    }
 
    const size_t count = channel_view(channels[0]).count;
    if (count == 0) {
        MF_ERROR(Journal::Component::Kakshya, Journal::Context::Runtime,
            "as_point_vertex_access: position channel (slot 0) is empty or unsupported");
        return std::nullopt;
    }
 
    VertexAccess va;
    va.conversion_buffer.resize(count * 60);
    assemble_vertices(channels, count, config, config.default_size,
        va.conversion_buffer.data());
    va.data_ptr = va.conversion_buffer.data();
    va.byte_count = va.conversion_buffer.size();
    va.layout = VertexLayout::for_points();
    va.layout.vertex_count = static_cast<uint32_t>(count);
    return va;
}

References b, MayaFlux::Kakshya::VertexAccess::byte_count, MayaFlux::Kakshya::VertexAccess::conversion_buffer, count, MayaFlux::Kakshya::VertexAccess::data_ptr, MayaFlux::Kakshya::VertexAccessConfig::default_size, MayaFlux::Kakshya::VertexLayout::for_points(), MayaFlux::Journal::Kakshya, MayaFlux::Kakshya::VertexAccess::layout, MF_ERROR, MayaFlux::Journal::Runtime, and MayaFlux::Kakshya::VertexLayout::vertex_count.

Referenced by as_vertex_access(), and MayaFlux::Buffers::DataWriteProcessor::upload_vertex().

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