SMP · Subject Builder (legacy)

The Subject Builder is where a character starts in the SMP pipeline. It packs the who - age, gender, expression, hair, pose - into a Subject record and appends it to a PROMPT_DICT's subjects list. The append part is the feature: chain two of these and you've got a two-person scene without copy-pasting a character description into both prompts.

It's a builder node in the legacy SMP suite, so it doesn't generate anything by itself. It just makes structure. What you get out of it is a PROMPT_DICT that downstream nodes - the Aggregator, the Structured Prompt Assembler - can actually route, which is the whole reason to use SMP instead of one big hand-typed prompt.

How it works

The node builds a subject dict from its widgets - subject_id, age_desc, gender, expression, hair_color_length, pose_hint - then merges in extra_json for anything the fixed fields don't cover (skin tags, eye description, body build, whatever you want). If you connect a subject_dict instead, that dict wins outright and the widgets become decoration. The new subject is appended via a list-merge, so feeding builder one's output into builder two's prompt_dict_in grows subjects[0], subjects[1], and so on.

The extra_json is where the detail lives. The default gives you skin_tags plus expression; the SMP reference workflow shows the habit worth stealing - put eye_desc, brow_desc, lip_desc, and body_build there so your character doesn't come out as a featureless mannequin.

The inputs that matter

• gender, age_desc, expression, hair_color_length - the character's headline traits.
• pose_hint - free-text pose, goes straight into the assembled prompt.
• extra_json - the fine detail, as JSON.
• prompt_dict_in (optional) - the chain input; feed the previous builder's output here.

Outputs

• prompt_dict - the growing dict. Wire it into the next builder, or into SMP · Aggregator.

Install

No extra dependencies. Base pack install only:

cd ComfyUI/custom_nodes
git clone https://github.com/ping1979ping/comfyui-FVMtools

Restart ComfyUI.

Common issues

Malformed extra_json is silently ignored - a stray comma and your skin tags just don't appear, with no error to chase. And the classic wiring mistake: if your second builder overwrites the first person instead of adding a second, you've connected them in parallel. Chain the first builder's prompt_dict output into the second builder's prompt_dict_in input - that's the append path.