Conclusions First
To produce skeleton straight characteristics (upper body thickness, shoulder width, straight body lines), broad shoulders was the most effective. Increased upper body volume and wider shoulders were confirmed in all 3 images. firm texture also showed upper body volume increase. On the other hand, tailored fit changed the clothing to a suit-style outfit, making it unusable for body type control. straight body, structured, and rectangular showed no difference from the control.
Experiment Design
| Parameter | Value |
|---|---|
| Model | z-image-turbo (6B, photorealistic distilled) |
| Steps | 8 |
| Sampler | euler |
| Scheduler | ddim_uniform |
| CFG | 1.0 |
| Size | 1024x1024 |
| Seeds | 3 fixed (consistent across all conditions) |
| Per condition | 3 images (3 seeds) |
| Total | 8 conditions = 24 images |
Base Prompt
White background + tank top + jeans standardized to clearly observe body silhouette.
A00: control
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: Seed 1 is slightly broad-shouldered with a standard body type — gentle waist curve. Seed 2 is slim with narrow shoulders and thin upper body. Seed 3 is similarly slender with narrow shoulders. All 3 images have no upper body volume — standard slim build.
A01: straight body
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: Seed 2 shows no notable difference from control. Shoulders, waist, and body lines are the same slim build as control. The upper body thickness and straight lines characteristic of skeleton straight are not visible.
A02: firm texture
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: Seed 1 shows increased upper body volume compared to control. Bust area is larger with the tank top fabric pulling tight. Seed 2 also shows more thickness in the upper body with added volume from shoulders through chest. However, “firm texture” is a texture description — the body change may be a secondary effect.
A03: broad shoulders
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: Clear difference from control in all 3 images. Seed 2 changes from a slim build to wider shoulders with more upper body volume. The tank top strap spacing widens and the line from shoulders to arms becomes solid. Seeds 1 and 3 similarly show expanded shoulders and a larger overall upper body frame. The closest change to skeleton straight’s “upper-body-weighted build.”
A04: structured
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: No difference from control. Seed 2 remains slim with no change in shoulder/waist/hip balance. “Structured” appears to affect clothing or composition more than body type — no body type effect confirmed.
A05: tailored fit
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: All 3 images changed from tank top + jeans to a white suit-style set. Seed 1 shows a V-neck short-sleeve wrap top + white wide pants; seed 2 similarly shows a peplum top + white pants; seed 3 shows a long-sleeve V-neck top + white pants. “Tailored fit” functions as a word that shifts clothing toward formal — not usable for body type control. It overrides the base prompt’s “white tank top, fitted jeans.”
A06: rectangular
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: No difference from control. Seed 2 remains the same slim build with no change. “Rectangular” is not being interpreted as a straight-line body silhouette.
A07: inverted triangle
| seed 1 | seed 2 | seed 3 |
|---|---|---|
 |  |  |
Observation: No difference from control. Seed 2 shows the same shoulder width and upper body volume as control. “Inverted triangle” was intended to produce wider shoulders and narrower hips, but no effect on body type was confirmed.
Summary
| Condition | Body Change | Side Effects |
|---|---|---|
| straight body | No difference | None |
| firm texture | Upper body volume increase | Texture description — may have unintended effects |
| broad shoulders | Shoulder widening, upper body volume increase | None |
| structured | No difference | None |
| tailored fit | Cannot evaluate | Clothing changes to suit |
| rectangular | No difference | None |
| inverted triangle | No difference | None |
To produce skeleton straight characteristics, broad shoulders is the most effective. Stable shoulder expansion and upper body volume increase are achieved. firm texture also contributes to upper body thickness, but as a texture description it may produce unintended effects.
Reproducing all skeleton straight characteristics (upper body thickness + waist straightness + flesh) with one keyword is difficult. The realistic approach is to use broad shoulders as the base and combine with other body descriptors.
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