CompuServe Messages

Judy: >> "ChooseNode "Select Parent Object", 127-NT_AMBIENT-NT_TARGET << Well, this line of code is kinda cute. The filter parameter reflects our handling of what are known (in lower-level languages like C) as bit flags. Since Keyscript and TSE don't do binary, we use integer values which, when added together, produce completely unique values. In the case of object/node types, you've got the following choices: NT_OBJECT 1 NT_CAMERA 2 NT_TARGET 4 NT_LIGHT 8 NY_SPOTLIGHT 16 NT_AMBIENT 32 NT_DUMMY 64 The names, such as "NT_OBJECT" are merely constant names for the associated value. If you PRINT NT_LIGHT, you'll get an "8". So, if you wanted to have an object selection box appear which only listed the lights in the scene, you'd use a line such as: ChooseNode "Select a light", NT_LIGHT + NT_SPOTLIGHT + NT_AMBIENT Which is the same as saying: ChooseNode "Select a light", 56 because 8 + 16 + 32 = 56. What the programmer has done in the line which is confusing you, is he's said that he wants everything EXCEPT the ambient light and any spotlight targets to appear in the node selection dialog. Hence he's added up all the values, and SUBTRACTED the node types he doesn't want. 1 + 2 + 4 + 8 + 16 + 32 + 64 = 127 1 + 2 + 8 + 16 + 64 = 91 His approach is more efficient than this approach: ChooseNode "Select parent object", NT_OBJECT + NT_CAMERA + NT_LIGHT + NT_SPOTLIGHT + NT_DUMMY -Martin