13.003 Computational Geometry and Visualization

13.003 Computational Geometry and Visualization

OpenGL Drawing Style

While the geometric primitives describe what should be drawn, they do not specify how things should be drawn. The appearance of the geometry is controlled by setting the values of the OpenGL state.

State values for things such as color, line width, etc. stay into effect until changed.

Color

glColor{34}{sifd}(red, green, blue [, alpha]);

The alpha value is used to specify transparency.

Points

```
float size;
glPointSize(size);
```
where size is specified in pixels.

Lines

```
float width;
glLineWidth(width);
```
where width is specified in pixels.
```
int factor;
short pattern;
glLineStipple(factor, pattern);
```
where factor scales the bit pattern, and pattern is the repeating bit pattern. Each bit of pattern specifies the on/off state of a pixel.
Note: this function only defines the current line pattern. To actually begin to use the pattern, call the function:
```
glEnable(GL_LINE_STIPPLE);
```
To finish the use of the pattern, call:
```
glDisable(GL_LINE_STIPPLE);
```

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