Mirror entities in sketch in Solidworks - Cell-by-Cell Formula Trace

Sample Data

Coordinates of a line segment and a mirror line in a 2D sketch. The goal is to find the mirrored line coordinates across the mirror line.

Cell	Value
A1	Line1 Start X
B1	Line1 Start Y
A2	2
B2	3
A3	5
B3	7
A4
B4
D1	Mirror Line X1
E1	Mirror Line Y1
D2	4
E2	0
D3	4
E3	10
D4
E4
G1	Mirrored Line Start X
H1	Mirrored Line Start Y
G2
H2
G3	Mirrored Line End X
H3	Mirrored Line End Y
G4
H4

Formula Trace

MirrorPoint(Px, Py, Mx1, My1, Mx2, My2) = Reflection of point (Px, Py) across line through (Mx1, My1) and (Mx2, My2)

Step 1: Calculate mirror line vector: dx = Mx2 - Mx1, dy = My2 - My1

Step 2: Calculate vector from mirror line start to point: px = Px - Mx1, py = Py - My1

Step 3: Calculate projection scalar t = (px*dx + py*dy) / (dx*dx + dy*dy)

Step 4: Calculate projection point on mirror line: proj_x = Mx1 + t*dx, proj_y = My1 + t*dy

Step 5: Calculate mirrored point coordinates: mirrored_x = 2*proj_x - Px, mirrored_y = 2*proj_y - Py

Step 6: Repeat steps 2-5 for line end point (5,7)

Step 7: Final mirrored line coordinates: Start (6,3), End (3,7)

Cell Reference Map

    A     B       D     E       G     H
1 |Line1 Start|Line1 Start|Mirror |Mirror |Mirrored|Mirrored
  | X        | Y        |Line X1|Line Y1|Line X  |Line Y  |
2 | 2        | 3        | 4     | 0     |       |        
3 | 5        | 7        | 4     | 10    |       |        
4 |          |          |       |       |       |        

Cells A2:B3 hold original line start and end points. Cells D2:E3 hold mirror line start and end points. Cells G2:H4 will hold mirrored line coordinates.

Result

    A     B       D     E       G     H
1 |Line1 Start|Line1 Start|Mirror |Mirror |Mirrored|Mirrored
  | X        | Y        |Line X1|Line Y1|Line X  |Line Y  |
2 | 2        | 3        | 4     | 0     | 6     | 3      
3 | 5        | 7        | 4     | 10    | 3     | 7      
4 |          |          |       |       |       |        

Mirrored line coordinates appear in columns G and H. The original line from (2,3) to (5,7) is mirrored across the vertical line x=4 to (6,3) to (3,7).

Sheet Trace Quiz - 3 Questions

What is the vector direction of the mirror line?

A (10, 0)

B (4, 4)

C (0, 10)

D (2, 3)

Key Result

Mirror entities in sketch reflect points across a defined mirror line by projecting points onto the line and reflecting them symmetrically.

Practice

1. What is the main purpose of using Mirror Entities in a SolidWorks sketch?

easy

A. To delete half of the sketch entities automatically

B. To rotate sketch entities by 90 degrees

C. To create a symmetrical copy of selected sketch entities about a centerline or axis

D. To convert 2D sketches into 3D models

Solution

1. Step 1: Understand the Mirror Entities function

   Mirror Entities creates a symmetrical copy of selected sketch parts about a chosen centerline or axis.

2. Step 2: Identify the correct purpose

   It does not rotate, delete, or convert sketches but duplicates them symmetrically.

3. Final Answer:

   To create a symmetrical copy of selected sketch entities about a centerline or axis -> Option C

4. Quick Check:

   Mirror Entities = symmetrical copy [OK]

Hint: Mirror needs a centerline or axis to create symmetry [OK]

Common Mistakes:

• Thinking Mirror rotates entities
• Assuming Mirror deletes entities
• Confusing Mirror with 3D conversion

2. Which of the following is the correct step to start mirroring entities in a SolidWorks sketch?

easy

A. Select the entities, then click 'Mirror Entities' and choose the mirror line

B. Draw a circle and use 'Mirror Entities' without selecting anything

C. Right-click the sketch and select 'Convert Entities' before mirroring

D. Use the 'Trim Entities' tool before mirroring

Solution

1. Step 1: Identify the correct workflow

   You must first select the entities you want to mirror.

2. Step 2: Apply Mirror Entities tool

   After selecting, click 'Mirror Entities' and then select the mirror line (centerline or axis).

3. Final Answer:

   Select the entities, then click 'Mirror Entities' and choose the mirror line -> Option A

4. Quick Check:

   Select entities + Mirror + mirror line = correct steps [OK]

Hint: Always select entities before using Mirror Entities tool [OK]

Common Mistakes:

• Trying to mirror without selecting entities
• Using unrelated tools like Convert or Trim first
• Not choosing a mirror line

3. Given a sketch with a centerline and a rectangle on one side, what happens when you mirror the rectangle about the centerline?

medium

A. The original rectangle moves to the opposite side

B. A symmetrical rectangle appears on the opposite side of the centerline

C. The rectangle duplicates but overlaps the original

D. Nothing happens unless you redraw the rectangle

Solution

1. Step 1: Understand mirroring about a centerline

   Mirroring creates a copy reflected across the centerline, not moving the original.

2. Step 2: Predict the result

   The rectangle appears symmetrically on the opposite side, separate from the original.

3. Final Answer:

   A symmetrical rectangle appears on the opposite side of the centerline -> Option B

4. Quick Check:

   Mirror = symmetrical copy, original stays [OK]

Hint: Mirror copies entities, original stays in place [OK]

Common Mistakes:

• Thinking original moves instead of copying
• Assuming overlap without offset
• Believing mirror requires redrawing

4. You tried to mirror entities but the mirrored copy does not appear. What is the most likely cause?

medium

A. The sketch is fully defined

B. The entities were not selected before mirroring

C. The entities are already mirrored

D. No centerline or axis was selected as the mirror line

Solution

1. Step 1: Check mirror line selection

   Mirror Entities requires a centerline or axis to reflect about; missing this causes no mirrored copy.

2. Step 2: Confirm other conditions

   While selecting entities is important, the key cause for no mirror is missing mirror line.

3. Final Answer:

   No centerline or axis was selected as the mirror line -> Option D

4. Quick Check:

   Mirror line missing = no mirror copy [OK]

Hint: Always select a mirror line to see mirrored entities [OK]

Common Mistakes:

• Forgetting to pick the mirror line
• Assuming full definition blocks mirroring
• Thinking entities can be mirrored twice automatically

5. You have a complex sketch with multiple entities on one side of a centerline. You want to mirror them but exclude one specific entity from the mirror. What is the best approach?

hard

A. Select only the entities you want mirrored, excluding the one to omit, then apply Mirror Entities

B. Mirror all entities and then delete the unwanted mirrored entity

C. Draw the excluded entity after mirroring everything

D. Use the Trim tool to remove the unwanted mirrored entity

Solution

1. Step 1: Select entities carefully before mirroring

   Mirror Entities only copies selected entities, so exclude the one you don't want mirrored.

2. Step 2: Avoid extra cleanup

   Mirroring only needed entities avoids deleting or trimming later, saving time and errors.

3. Final Answer:

   Select only the entities you want mirrored, excluding the one to omit, then apply Mirror Entities -> Option A

4. Quick Check:

   Select entities carefully to control mirror output [OK]

Hint: Pick only entities to mirror, exclude others before mirroring [OK]

Common Mistakes:

• Mirroring all then deleting unwanted copies
• Drawing excluded entities after mirror causing misalignment
• Using Trim tool which doesn't remove mirrored copies