Sced Tutorial 1

Getting Started

Sced Version 0.93

The best way to do this is to run Sced while you're reading and perform the operations as they are described.

Conventions

The Tutorial

1. We'll start by creating a cube. Select Object/New/Cube. A cube will appear at the origin. Notice also that the Edit menu (the last button on the left) is sensitive to input. Before creating the cube it was grayed out, or desensitized.
2. The sensitive Edit button indicates that there is something ready to be edited. Not surprisingly, it's the cube that was just created. All new objects in the scene window are placed on the edit menu at the time of creation. Many people ask why there is an edit menu at all. The reason is that there can be many objects on the queue to be edited at any one time, but only one object can actually be edited at a time. So the menu allows you to see which objects are available at any time (it visualizes the queue). Anyway, select Edit/Cube_0. A large dialog window will pop up. Place it somewhere where it is easy to reach but not in the way, because it will stay up indefinitely (unless you explicitly close it). The cube should also have changed.
3. Take a look at the cube. There are several things to take notice of.
   • First is the large circle around the outside. That is the arcball circle, which is helpful when using the rotation interface. It doesn't actually do anything if clicked on.
   • The cube itself has changed color, to indicate that it is the object being edited.
   • A small green circle has appeared at the center of the cube. This indicates the Origin Point of the cube.
   • A small red square has appeared at one corner of the cube. This indicates the Scaling Point for the cube.
   • You should notice a line on top of each of the X and Z axes. These are the cube's Major and Minor Axes. The Major one is the longer one, under the Z axis.
   All these features are used for editing the object.
4. Take a look at the Edit dialog box. It contains several buttons in the top left corner, and then a sequence of boxes, each of the same basic type. The buttons control editing commands. There is one box for each feature. So for the cube there is are Origin, Major Axis, Minor Axis and Scaling boxes. Each box contains:
   • A button for changing the location of the feature relative to the object. That's the button or menu with the name of the feature on it.
   • A box containing a set of toggles. Each toggle is a Constraint that may be placed on the feature. So Origin has 3 possible constraints and Major Axis has 1.
   • An Add menu, to add new constraints to the set of available constraints.
   • A Modify button, to change the definition of a constraint, or delete it from the set (a rather extreme form of modification).
   For this tutorial we will stick to the default constraints as provided. Hence we will not use Add or Modify at all, nor will we change how a feature relates to the object. The default constraints are actually the standard constraints on 3d motion provided by most drawing packages. They constrain the object to move along one of the orthogonal axis planes, or rotate about the significant axes of a body (free rotation is also possible).
5. Note that if anything goes wrong, Undo will either undo or cancel an operation, whichever is meaningful. It can undo all the way back to the start of the current edit session (when the object was chosen off the edit menu).
6. So lets move the cube around. First you must select some constraint on the Origin, so that Sced knows how to translate 2d mouse motion into 3d. Lets try X-Y Plane This constrains the Origin Point to stay in the same X-Y plane that it is currently in. In other words, it restricts motion to be in the plane parallel to the X-Y plane. To select this constraint, click on X-Y Plane under the Origin. It should toggle on. In the main window should appear a square centered on the Origin. This indicates that that the Origin is constrained to a plane, and shows which plane it is constrained to.
7. Notice the cursor change as you move the mouse around with the button up. The 2 little arrows indicate that rotation will take place if you push the button down at that point. The funny inverted cross thing says that translation will take place if you button down there. A circle says that nothing can/will happen if you button down there. There is also a double ended arrow that indicates scaling, but it will not appear in the current configuration.
8. To move the object, click on the green Origin Point and drag. The cube will move around under the mouse, all the while staying in the constraint plane. It's that simple.
9. To move in a different plane, deselect the current constraint and choose another from the same set.
10. If 2 plane constraints are selected, say the X-Y and Y-Z, the square in the screen turns into a line pointing in the Y axis direction. That is because, if more than one constraint is selected, Sced takes the geometric intersection of all the constraints, in this case the 2 planes. The intersection of the 2 planes selected is a line in the Y direction. Dragging now will move the object along that line. Selecting the Z-X plane changes the line to a circle, indicating that the intersection of all the constraints is a circle, and hence the object cannot move (note the circle cursor when over the Origin).
11. By now you probably have no idea where the cube is in space. The best way to find out is to rotate the view and see how the cube moves. It's easier if there are other objects in the scene.
12. The easiest way to change the view is to hold down the shift key and drag the mouse. The view will rotate about the origin of the world, or the Look At point. The same effect can be achieved by selecting View/Viewpoint, but now you don't have to hold down any keys, but you do need to select the Apply button to explicitly cancel the view change. This method also has the advantage of allowing you to enter a viewing direction in the little window at the bottom of the Sced window.
13. You can also Zoom in and out using the + and - keys. Or you can set a zoom explicitly using Window/Zoom.
14. Panning works like changing the viewpoint, but uses the Alt or Meta key instead of shift. It also has an entry on the View menu.
15. You can change which way is Up and which point is the center of the view using View/Look Up and View/Look At. Each requires you to select points from the scene to define the new up or at direction. To select a point simply click inside the little red square that appears, or type in a vector at the bottom and click on Apply or hit return. Look Up requires 2 points, which form the endpoints of the new up vector. In general you only change Up once. For VRML it should be defined as the Y axis.
16. Finally you can change the viewing distance (the distance from the Look At point to the viewplane, or the eye distance (the distance from the viewplane to the center of projection) using View/Distance and View/Eye respectively.
17. Back to the cube. It should still be in edit mode. To rotate the cube, just button down and drag anywhere outside of the Origin and Scaling points (where the cursor is 2 little arrows). You can constrain the rotation axis by selecting either of the default constraints under Major or Minor Axis in the Edit window. Large arcs appear to indicate the constraint axis.
18. To scale the cube, constraints must be applied to the Scaling Point (similar to the Origin Point). In fact it works the same way, but now instead of the object moving when you drag in the red point, it is scaled. The defaults are different to. The planes are now parallel to the various axes of the object. Play with it to figure out which is which. The same rules for constraint combination apply.
19. To finish with the cube, click on Finish in the Edit window.
20. Now lets make it into a scene that's actually useful. First, attributes for the cube. Highlight the cube by dragging a rectangle that contains any edge or edges of the cube. Use button 1, because it selects. Button 2 or 3 unselects.
21. Choose Object/Attributes. A dialog appears with lots of attribute choices. Change them as you wish. All values should be between 0 and 1. Click on Done when ready.
22. Now choose Object/Name, and enter a new name for the object. Notice that it's still selected. So after setting the name, deselect it (drag over with button 2 or 3).
23. We need some lights. Select Light/Ambient and enter 0.2. That sets the ambient light level. If only one value is entered it is taken as white light.
24. Also choose Lights/Point. A light is created at the origin of the scene. Select Edit/Light_0 and the Edit dialog will pop to the front. Notice now that the only feature is the Origin, because that is all that defines a point light source. You can move the light around using the same techniques as for the cube. Select Finish when done.
25. Select the light (by dragging over it), and choose Object/Attributes. The attributes will just be a single color set. Try 0.8 (it works just like ambient).
26. Deselect the light. We're almost done.
27. Every scene needs a camera. Go to Camera/Edit Values and click on Viewport. This matches the camera to the current view of the scene. Then select Done.
28. That should be it. Select Target and your desired target renderer.
29. Select File/Save and enter a filename. Starting.scn is probably a good one.
30. Select File/Export to export the scene. Choose a name.
31. To exit, use File/Quit.

That's it. Somewhere you now have a file containing a description of a cube and a light in the format of your choice. Render it using your normal rendering method.