Single light, one shadow: inspect direction while the object stays still

01Prepare the inputs

1. Start with a matte object and one readable cast shadow on a plain surface. The supplied arch block is lit from the upper left and casts toward the lower right.
2. Keep the object base and a ground seam visible. They let you separate changing shadow shape from an object sliding across the table.
3. Ask the single soft key to move slightly toward the upper center, not around the full object. Avoid adding rim light, rotating the camera or changing background color.
4. Use direction and continuity as the acceptance target. Exact shadow length, illuminance and material reflectance require measured lighting or a render, not this visual prompt.

02Prompt and procedure

Copyable prompt

Start from the uploaded matte arch block. The block and camera remain completely fixed, with the block resting on the same tabletop contact. There is one soft key light, initially from the upper left. That one light shifts slowly a small distance toward the upper center and then stops. The single cast shadow responds smoothly, turning from lower right slightly toward lower center and becoming a little shorter, while staying attached at the block base. The lit and shaded sides change gently in agreement with that shift. Preserve the arch opening and matte surface. No second shadow, no moving object, no camera motion, no glow or extra light source.

1. Read the initial light-shadow pair

   Confirm that the bright upper-left side and lower-right floor shadow are consistent in the input. A source with several competing shadows cannot isolate a single-light test.

2. Move only the key

   Describe a small shift toward the upper center while keeping object and camera fixed. Do not ask for a rotating product reveal; it changes the cause of the shadow movement.

3. Follow the contact end of the shadow

   Watch the shadow where it meets the base before judging its distant tip. It should stay anchored while its extent and direction change, rather than detach as a drifting dark shape.

4. Cross-check surface shading

   Compare the block face and shadow at the start and end. If one changes in the opposite sense or a second shadow appears, simplify the light shift and inspect the same relationship again.

03Check the result

• The block and its tabletop contact stay fixed.
• The arch opening remains the same shape and stays open.
• There is one readable cast shadow rather than new competing shadows.
• The shadow remains attached at the block base.
• Its direction changes smoothly from lower right toward lower center.
• The shadow shortens slightly without teleporting or crossing through the block.
• Face shading changes coherently and the final light/shadow state holds still.

04Troubleshoot and finish

End after the light stops, with one attached shadow and a stationary arch. Record the qualitative direction check rather than claiming a measured relighting solution.

05Download the practice files

• Original illustrated practice input ↓
• Editable original source SVG ↓
• English task brief ↓
• Chinese task brief ↓
• Bilingual inspection sheet (blank results) ↓
• English practice instructions ↓
• Chinese practice instructions ↓