Since the communication between the GPU and the rest of the PC is relatively slow, this stage can help you reduce the amount of data that needs to be transferred. It takes the primitives from the shape assembly stage as input and can either pass a primitive through down to the rest of the pipeline, modify it first, completely discard it or even replace it with other primitive(s). Unlike the vertex shader, the geometry shader can output more data than comes in. The following step, the geometry shader, is completely optional and was only recently introduced. These reduce the number of vertices you need to pass if you want to create objects where each next primitive is connected to the last one, like a continuous line consisting of several segments. There are some additional drawing modes to choose from, like triangle strips and line strips. These shapes are called primitives because they form the basis of more complex shapes. This is where the perspective transformation takes place, which projects vertices with a 3D world position onto your 2D screen! It also passes important attributes like color and texture coordinates further down the pipeline.Īfter the input vertices have been transformed, the graphics card will form triangles, lines or points out of them. The vertex shader is a small program running on your graphics card that processes every one of these input vertices individually. Commonly used attributes are 3D position in the world and texture coordinates. Each of these points is stored with certain attributes and it's up to you to decide what kind of attributes you want to store. It all begins with the vertices, these are the points from which shapes like triangles will later be constructed. I'll explain these steps with help of the following illustration. The graphics pipeline covers all of the steps that follow each other up on processing the input data to get to the final output image. To top that all, the exercises at the end of this chapter will show you the sheer amount of control you have over the rendering process by doing things the modern way! That inevitably means that you'll be thrown in the deep, but once you understand the essentials, you'll see that doing things the hard way doesn't have to be so difficult after all. By learning OpenGL, you've decided that you want to do all of the hard work yourself.

Hello triangle in opengl es 2.0 example