Learn CAD sketch constraints by predicting how a line changes

Predict before applying the constraint

In Fusion, enter Edit Sketch and draw a sloping line away from the origin, clearly closer to horizontal than vertical. Check for automatically added constraints: the exercise needs a line whose orientation is still free, so redraw or remove an unwanted relation in this practice sketch if necessary. The Horizontal/Vertical constraint tool is available in the sketch context and constrains the selected line to whichever axis is nearer. If your CAD app offers separate horizontal and vertical relations, choose Horizontal. Before selecting the line, predict: will its orientation change, will its length change, and will its position become fixed?

For feedback, show the sketch canvas, the line, the active sketch/edit context, and the constraint controls if they are visible. Make sure the line is selected before asking about the command. If labels or the selected geometry are too small, zoom in or type the control name; hide private project details.

Apply it, then check what remains free

Apply the horizontal relation yourself. In Fusion, the Horizontal/Vertical tool chooses the nearer axis; the line should align with that axis and show a constraint badge. Compare the before and after stills to discuss the visible orientation change. Do not estimate an exact angle or length from pixels.

A constraint expresses a geometric relationship; a dimension specifies a measurement such as a line's length or distance from the origin. A horizontal relation alone does not set line length, and it may not anchor the line's position. Use the sketch's native constraint or degrees-of-freedom status, and, where appropriate, test whether an endpoint can still be dragged. Add a dimension or location constraint only if your design intent requires it.

Try a nearby constraint without a step-by-step answer

Draw a second free line that is clearly nearer vertical. Before using Fusion's Horizontal/Vertical tool, predict which axis it will choose and whether its length or position will also be fixed. Apply the tool, inspect the constraint badge and native sketch status, and explain how this result differs from the first line. In another CAD app, use its equivalent relation and verify the result with that app's own constraint indicator or degrees-of-freedom tool.

Keep a short record so you can compare your prediction with what the solver did. If you need an exact length or coordinate, read it from the CAD dimension or property panel and enter it in text; do not ask an image model to infer precision from the drawing.

Keep a prediction and result record

Concept: horizontal constraint on a free line
Before: line orientation and sketch mode
My prediction: what will change; what will stay free
Action: constraint I applied myself
Visible result: what changed in the sketch
Native check: constraint badge, dimensions, and remaining degrees of freedom
Transfer: prediction and result for a second line

Use a screenshot only when it helps explain the state

A direct screenshot attachment is simplest for one question. If a compatible screen-capture source is already connected, you can request a still before and after your action. Each image is requested separately; the assistant does not watch the screen continuously or edit the CAD project. Keep native dimensions and constraint status as the source of truth.

Prompt to adapt

I am learning sketch constraints. Use the screenshot I attached; if I have not attached one and a screen-capture source is already connected, request one still. First tell me whether you can see an active sketch and a selected line; ask me to confirm anything unclear. Before I act, ask me to predict what a horizontal constraint will change and what it will leave free. Wait for my prediction. I will apply the constraint myself. After I attach a new screenshot or request another still, compare the visible result with my prediction. Do not estimate exact angles, dimensions, or hidden constraint state from pixels. Ask me to check those in the CAD tools, then give me a second line to constrain as a transfer exercise. Do not edit the project.

Source documentation

• Autodesk Fusion Help: Horizontal/Vertical constraint
• Autodesk Fusion Help: Dimensions in sketches
• Autodesk Fusion Help: Fully define and constrain sketches

Set up without starting a capture

Set up your MCP client with the full tool reference. The separate capture page can replace the active capture page for your account. It does not take a photo by itself.