# GL_TRIANGLE_STRIP vs GL_TRIANGLE_FAN

I need an example of a polygon that can be done only by `GL_TRIANGLE_STRIP`

and another polygon that can be done only by `GL_TRIANGLE_FAN`

.

## Answers:

When knowing the difference between *Triangle Strip* and *Triangle Fan* a shape will be easy to make.

## Triangle Strip

For instance a *Triangle Strip* is a set of connected triangles which share vertices.

### Example of Triangle Strip

Using *Triangle Strip* we will be able to get the following output, using those given vertices.

## Triangle Fan

Where a *Triangle Fan* is also a set of connected triangles, though all these triangles have a common vertex, which is the central vertex.

In OpenGL the central vertex is the first given vertex, in the *Triangle Fan*.

### Example of Triangle Fan

Using *Triangle Fan* and the same vertices as in the other example, we will only be able to get the *colored area* as output. That is due to the importance of the arranged order of the vertices in *Triangle Fan*. **Basically,** all the vertices need to go around the central vertex.

## Conclusion

As you can see on our 2 example sets of vertices those "output shapes" are unique to both *Triangle Strip* and *Triangle Fan*.

### Extra

*I made a similar answer here, you can read it if you want, I actually used the same images since the questions are closely related.*