User:Arch dude/Spin a goblet
The spin technique is a good choice when you want to model an object that is radially symmetric and you know what the cross section of the object looks like. This the the virtual equivalent of using a lathe to create an object in the real world. With the spin technique, we draw an outline of one half of the outline of the object, and then spin the outline about an axis to create the object's mesh.
Modeling[edit| edit source]
Here is a real-world goblet. The picture is not an orthographic image, so we cannot directly copy the outline, but it is close.
Setup[edit| edit source]
We now model the outline. Let's start with the default model. We want to create an initial object consisting of a two-dimensional outline, so select the cube, go to edit mode, and delete all the vertices. This leaves us with an object that has no vertices as a nice place to start. We want the resulting goblet to sit at the origin with the Z axis as its axis of symmetry so we get a front view. Since we will be working directly with mesh vertices, the manipulator is a hindrance, so turn it off.. (With the manipulator on, it is easy to accidentally move a vertex out of the editing plane, but we want a 2D cross-section.) We are now ready to create the two-dimensional outline as a chain of vertices with the first and last vertices on the axis.
First Vertex[edit| edit source]
Now, place the first vertex: this will be the center of the bottom of the goblet, so place it slightly above the origin on the Z axis. Why? Well, for two reasons: in the real world, the bottom of a goblet is not actually flat. Instead. the rim is lower than the center of the bottom, so the bottom is concave and the goblet sits on a flat surface without wobbling. The second reason is that we intend to use the "subsurf" technique, and this technique will make a flat surface slightly convex in our virtual world, so we will preemptively start the bottom of the base with a slightly concave surface.
Finish the outline[edit| edit source]
Add the second vertex, which will be on the rim of the goblet's base: move the cursor to the X axis at about -3, and add a vertex. Add additional vertices to your outline by moving the cursor to the desired location and adding, for as many vertices as you need to accurately model the outline. Since you will be using subsurf later, make sure that you place two vertices near each other when you need a sharp curve in your outline. Otherwise, subsurf will convert your sharp curve into a wide smooth curve. This is wonderful advice, but it won't work, because Blender interprets the + differently when you attempt to place an extruded vertex too near the vertex from which you are extruding. One quick way around this is to create your vertices sufficiently far from each other to avoid the problem, and then come back and move them to the correct spots later.
Eventually, you will place the last vertex, which will become the point at the bottom of the inside of the goblet. This point should be be on the Z axis. Your outline is done!
Spin[edit| edit source]
Now, to spin it. first, make sure that you are still in edit mode, and that the last vertex is selected. Set the cursor to the selection. Now, get a top view: you are now looking at your outline from the top, and it should look like a straight line along the X axis with one end at the cursor on the Z axis. (If this is not the case, select and move points to the X axis and check your work by switching back to the front view, then come back to the top view.) Now select the whole outline and then move to the button menu to perform the spin. Set the rotation to 360 and the count to 12 (or another number of your choice) and click on "spin." An elaborate circle will appear. Go to the front view to see your un-smooth goblet.
Finish up[edit| edit source]
Since you are in edit mode and you have the whole mesh selected, this is a good time to remove duplicate vertices. The two vertices on the Z axis (base bottom center and bulb bottom center) were duplicated 12 times, and the entire outline was duplicated once when the circle closed at the end of the spin. Remove the duplicates. If you fail to to this, the subsurf operation will create a cusp at the two centers, and a crease at the duplicated outline.
If you placed the two Z-axis vertices by hand, they may not be exactly on the axis, and therefore may still be duplicated, leaving a tiny "hole" at the axis. Fix this by merging each of the two sets separately:
- select the vertices to merge.
- merge at center.
Now start to smooth by using the subsurf in the button window. First add a modifier and select subsurf. Set levels to 2 Then, use smooth in the texture window. You now have a goblet model.
The image shows four objects: the two-dimensional outline, a smoothed version of the two-dimensional outline, the result of spinning the outline, and the result of subsurfing and smoothing. As you follow the procedure above, you will not actually have more than one object at a time as shown here.
Rendering[edit| edit source]
As with the other two goblets, It is difficult to fully evaluate the model unless you render it. However, a "pretty" rendering requires at least minimal materials, lighting, and scenery. This section is a cookbook approach to providing these minimal elements and is not really a useful tutorial, so we won't explain the concepts. These topics are treated at length in later tutorials. If you wish to explore these subjects in more depth, go to the appropriate tutorials.
- The Goblet material: plain glass.
- The tablecloth: A (non-existent) table with a white tablecloth, in a featureless room painted yellow.
- The lighting: one bright lamp.
Material[edit| edit source]
- Go to object mode and select the goblet.
- In the Materials button window, add a material to the goblet, and name it "glass."
- In the Material tab, set the color to black (set R, G, and B all to 0.000) Here, "Black" merely means "do not add any color." It does not mean that the goblet looks black.
- Set the Alpha to 0.1 (i.e., quite transparent.)
- In the "Mirror Transp" tab, click the Ray Trace button, set the IOR to 1.5, and set Depth to 6 (or higher on a very fast computer.)
Tablecloth[edit| edit source]
- In the main window, put the cursor at the origin and switch to top view. In object mode, add a plane and then scale it to quite large. This is your tablecloth
- Go to object mode and select the tablecloth.
- In the Material tab, set the color to white and set the Alpha to 1.000 (i.e., opaque.)
- In the Shaders tab, click on Trashado. This allows the tablecloth to show the ray traced shadow of your goblet instead of a fake shadow.
Camera and lighting[edit| edit source]
Render the scene. If you started with the default camera and light the scene will be too dark and the shadow effect from the lamp will not be too pretty. To fix this:
- move the lamp higher and farther away.
- turn up the intensity.
Now adjust the camera:
- shift to camera view
- dolly and aim the camera
- move the camera back some
Detailed keystrokes[edit| edit source]
- Default model:select file→new.
- Front view:press
- manipulator off: press + to bring up the Manipulator menu, then select Enable/Disable
- Place a vertex: + .
- Add a vertex:press + , or ,
- Move a vertex: select it with , move it with the cursor, and then press .
- Cursor to selection: ( + , then cursor→selection
- top view:
- Select all: once or twice, until all are displayed in yellow
- Remove duplicate vertices:press and select Remove Doubles
- Merge at center:Press ,Merge → At Center, confirm with or