3D Graphics Using OpenGL ES 2.0 - Beginning Android 3D Game Development - page 98

Listing 4-4. Simple Fragment Shader

// Fragment Shader
varying vec3 Color;
void main()
{
gl_FragColor = vec4(Color,1);
}

The gl_FragColor variable is a reserved variable that outputs the actual color of the fragment.
An example of a more complex fragment shader is shown graphically in Figure 4-13 . Here a texture,
texture coordinate, diffuse lighting, specular lighting, a light source, and an object material all
contribute to the final color of the object being rendered. I discuss these subjects in more detail later
in this chapter.

Material

From Vertex Shader Light

Texture

Texture Coordinate
Diffuse Lighting for Vertex
Specular Lighting for Vertex

Emissive
Ambient
Diffuse
Specular
Alpha

Ambient
Diffuse
Specular

Fragment Shader

Color (gl_FragColor)

Figure 4-13. Complex fragment shader

Overview of the Shader Class
The Shader class holds the vertex and fragment shaders, as well as functions that are used to send
data from the main application to the shader programs (see Figure 4-14 ).