Table of contents
What is this blog post?
What is open gl es?
What is a vertex?
What is a vertex shader?
What is a fragment?
What is a fragment shader?
Shader and Program objects
Resources
What is a vertex shader
Intro to shaders
Graphics pipeline
What is a fragment
Fragment shaders
My app on the Google play store
The app
This blog post contains all of my short notes on the open gl es hello world triangle
As it open gl es is just a wrapper around open gl to make it more efficient for mobile/memory limited devices
A vertex is nothing more than a coordinate in a 2d or 3d space. So each point on a tringle is considered to be a vertex
In the open gl es triangle tutorial we create the vertices for the triangle in this array:
0.0f, 1.0f, //x,y
-1.0f, -1.0f, // x,y
1.0f, -1.0f // x,y
};
Each of the x,y cordinates represent a vertex. So 0.0f, 1.0f is one vertex and so on
Documentation
programmable method for operating on vertices.
Below is just copy and pasted form the documentation
Vertex shaders are the most established and common kind of 3D shader and are run once for each vertex given to the graphics processor. The purpose is to transform each vertex’s 3D position in virtual space to the 2D coordinate at which it appears on the screen (as well as a depth value for the Z-buffer). Vertex shaders can manipulate properties such as position, color and texture coordinates, but cannot create new vertices. The output of the vertex shader goes to the next stage in the pipeline, which is either a geometry shader if present, or the rasterizer. Vertex shaders can enable powerful control over the details of position, movement, lighting, and color in any scene involving 3D models.
Graphics pipeline documentation
In the graphics pipeline there is a non-programmable(we can not touch it) step called Rasterization. Which turns our vertex data into points on the screen. Which it does by creating fragments, which is all the data necessary to generate a single pixel’s worth of a drawing.
fragment shader documentation
The fragment shaders give us a programmable method to take the previously mentioned fragment data and alter the fragment data
The fragment shaders provides a general-purpose programmable method for operating on fragments.
copy and pasted from OpenGL ES Programming guide
There are two fundamental object types needed to create to render with shaders
1) Shader objects: The source code is
given to the shader object and then the shader object is compiled into
object form (like an .obj file). After compilation, the shader object can then be attached to a program object.
2) Program objects: A program object gets multiple shader
objects attached to it. In OpenGL ES, each program object will need to have one vertex shader object and one fragment shader object attached to it (no more, and no less). The program object is then linked into a final “executable.” The final program object can then be used to render.
Conclusion
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