T U T O R I A L


· Contrary to other drawing primitives, a rendered spline looks completely different than it does during the modelling-process. Let's recall: we had three control- points, each with a radius of one grid-unit. On the other hand we have a thin blue line, which tells us nothing about the thickness of the object. Maybe an image can help ..




· As you can see, the resulting spline is some sort of »curved cylinder« with rounded ends, which has a radius of one grid-unit everywhere along the curve. This leads us to Fact No 3: the control-points of a spline in POVLAB do control the form of the curve itself AND its thickness. Considering this we can extract Fact No 4: altering the position of a control-point changes the form of the curve, whereas altering the size of a control-point changes the thickness of the spline at the respective section of the spline.
The »Spline-Playground«

· There is in fact an object in the final temple-scene, where splines are used - the lamp (see picture below).

· Of course a detailed explanation of how to create the splines used for the grip of the lamp would exceed the limit of this section. Therefore we have prepared a scene file (ca. 12kB), which you can download to examine. Click here to download this file.
Note: please read the documentation-files included in the archive »lamptut.zip«.

· If you're new to splines, just have a close look at the position and the size of the control points in the lamp- scene. Alternatively you can make a backup-copy of the scene-file and experiment a little bit with the splines of the lamp.

· Certainly we will do some spline-modelling later on, but before that we need to take a look at the functions neccessary for editing a spline, in the case we want to alter such an object somewhen.

Chapter B/Page 17

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