Document Reductions of GLM agent variables

[ptheywood]

This requires a custom reduction (assuming it works). Will be documented once tested as part of PRIMAGE.

[Robadob]

For the time being this on hold, there aren't current plans to add support for it to PythonAPI.

The C version is pretty simple (and hopefully obvious).

FLAMEGPU_CUSTOM_REDUCTION(glm_min, a, b) {
    return glm::min(a, b);
}
FLAMEGPU_CUSTOM_REDUCTION(glm_max, a, b) {
    return glm::max(a, b);
}
FLAMEGPU_HOST_FUNCTION(host_fn) {
    const glm::vec3 min_pos = FLAMEGPU->agent("agent").reduce<glm::vec3>("xyz", glm_min, glm::vec3(std::numeric_limits<float>().max()));
    const glm::vec3 max_pos = FLAMEGPU->agent("agent").reduce<glm::vec3>("xyz", glm_max, glm::vec3(-std::numeric_limits<float>().max()));
}