Constructive Solid Geometry

From DeleDWiki

Jump to: navigation, search
DeleD Interface

To give you more power and control over your scene and objects / primitives, DeleD offers union, subtraction (carve), split, intersection, and slice tools. These tools make it easy for you to create holes in objects, or to merge objects together. Constructive Solid Geometry (also referred to as CSG) operations are very easily performed in DeleD. Simply select two or more objects and press the desired CSG command you'd like to use. DeleD will use the last selected object as operator. For example, create a cube and a cylinder within that cube. Select the cube and then the cylinder and press Subtract. The result will be a hole in the cube having the shape of the cylinder.

Using CSG allows you to quickly create complicated objects easily. CSG is widely used to construct level geometry for games, such as doorways and windows.



  • CSG routines in general have a habit of creating many polygons in the resulting object, especially if applied on complicated objects. You should use the Lowpolygon Optimize function to cleanup your CSG result afterwards. This can be done automatically by setting the appropiate option in the Options screen. Also, cleaning up manually might be useful. Commands like Polygon Merge, Polygon Delete, Polygon Triangulate, Vertex Fill and Vertex Delete are helpful in that area.
  • Using the Options screen, you can specify if you want the operator object to be removed after the CSG operation has been completed. If you decide to keep the operator, you can immediately use it again on subsequent CSG operations.
  • If CSG is used on large, complicated objects, a progress indicator is shown. The number of polygons out of which an object must be made before the progres indicator is shown, can be set in the Option window.
  • The CSG routines might not handle coplanar polygons correctly. Try to avoid overlapping polygons in such cases or edit the resulting object manually after CSG has been applied.
  • Occassionally, if a polygon is accidentally removed during a CSG operation, you can repair this manually using various 3D editing functions. For example, Fill might come in handy here.


Union can be used to merge objects together. The two objects on the left are moved into each other resulting in the third object. Using the Union command results in the object on the right.


Subtraction (carving) Can be used to subtract objects from each other. This feature makes it very easy to create holes (like doors and windows) in objects. The cube on the left is moved into the second cube (resulting in the third object) after which subtraction is applied. This results in the object on the far right. Note: coplanar polygons are part of the final result so if you want to create holes using Subtraction, try to avoid overlapping (coplanar) polygons between the objects. This is why the cube being subtracted is slightly larger in certain dimensions than the object it is being subtracted from.


Split is a combination of intersection and subtraction and can be used to split an object into two separate objects using another object as a splitter. The cube on the left is moved into the cylinder after which splitting is applied. This results in the two objects objects on the far right.


Intersection returns those parts of objects that are inside all objects. Like this: the two objects on the left are moved into eachother. Using the Intersect function on those objects results in the new object on the right. Again, take special care about overlapping polygons between the objects. If needed, remove redundant polygons from the Intersection result.


Slice uses a plane to slice objects into two parts. The cylinder on the left is sliced by the rectangle which was placed on top of the cylinder. The result are the two objects on the right. Note that the rectangle doesn´t have to actually intersect with the object. Instead, it uses the plane of the rectangle to slice the object. Any object that only has one polygon can be used as slicing object.

Personal tools