T U T O R I A L

UNION AND MERGE

· The UNION-operation is very easy to understand. It is just a »glue-mechanism, that allows you to combine two or more shapes (see picture below).

· Very similar to the union is the MERGE-conjunction. In opposite to the union, you can supress the display of the combined shapes inner surfaces. Merging ist often used, when transparent objects are to be grouped.

DIFFERENCE

· A quite interesting feature is the DIFFERENCE. With this operation, you can cut out the overlapping zone from the base-shape, whereas the modifying shape is no longer displayed.

· There is one thing, you should care about, when using the CSG-difference. The modifying shapes leave their surface-parameters on the cut out section of the base object (as you can see in the picture to the left).

· If you want the cut out section to have the surface of the base object, then you must assign the same texture (color) to the base object and to the modifying object. 		INTERSECTION

· Last but not least, there is the INTERSECTION. This CSG-method is the oppsite of the difference (see picture below).

· The scene, that produced the left picture, still contains a base-object (the yellow cube) and a modifying-object (the red sphere). The intersection, only displays those points, that lie within the base- and the modifying-shape.

How POVLAB handles CSG-objects

· When you create a CSG-group in POVLAB, it is important in which order you select the components of the CSG-object. Let's check this out: A - load a standard-scene with a camera and at least one light. B - insert a cube - the base object - and a sphere - the modifier - into the scene. C - translate the objects, so that they overlap. D - choose the command »csg« | »difference« and click on the cube and then on the sphere. E - save the scene under a specific name and render it using the command »render« | »quick«. As you can see in the resulting image, the shape has been properly cut out of the cube. Now do the following: select the command »csg« | »remove csg« and click on the dotted line of the sphere (after this, the line gets solid again ). Create another difference, but this time, you click first on the sphere and then on the cube. Render the image and you will see the difference. For further studies download three sample-scenes by clicking here.
Chapter A/Page 16
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This page was last modified on: 1996-07-14