Boolean Operations in Initial Design Surface

First we will subtract the cylinder from the block to create a hole through the block.

Subtract the cylinder

1. Select OPERATIONS \ SUBTRACT or click the icon.

2. The user will be prompted in the status window to select the surface to keep, in the oblique view (left window), use the cursor to select the block.

3. The system then prompts for the surface to subtract, use the cursor to select the cylinder. After a short pause the window will redraw and display the block with the hole through the centre. If the user looks at the list of patches in the tree, it will be seen that the cylinder CLN no longer exists.

4. To show clearly that there is a hole through the block we will render it in isometric view. Rotate the isometric view so that the top and bottom edges of the hole overlap. Render the view by clicking the icon.

5. The opposite of the Subtract function is unite which combines two surfaces and removes any duplication. To use this function we must go back to the status of the model before we performed the subtract. This is achieved by using the Rollback buttons on the Surface window.

6. Unite the two entities by selecting OPERATIONS \ UNITE or click the icon., as with subtract the user is first prompted to select the surface to keep then the surface to unite. Select the block followed by the cylinder. Checking the patch list on the layer editor will show that the two patches have been united under the BLO identifier.

7. The last Boolean operation we will look at is Solid Intersection, this returns the common portion of two intersecting surfaces. First click the Left Rollback button to go back to the separate block and cylinder. OPERATIONS \ SOLID INTERSECTION or click the icon. then select the block followed by the cylinder. The result should be a cylinder of the same height as the block.

8. The user should now repeat the subtract, unite and solid intersection functions but this time select the cylinder first. The resultant surface in each case will have the name CLN. The results for unite and solid intersection will be the same as before but subtract will give two separate cylindrical portions stored as one surface.