Mali GPU User Interface Engine Application Development Guide

Tutorial on Constructing Custom Shaders6.4 Minimal shader programsThe shaders are not required to use all of the available uniforms and attributes. Example 6-12shows a simple vertex shader that assigns the interpolated value in the POSITION attribute to theglobal position variable gl_Position:Example 6-12 Identity vertex shaderattribute vec4 POSITION;void main(void){gl_Position = POSITION;};Example 6-13 shows a simple fragment shader that always outputs red as the fragment color:Example 6-13 Fixed-color fragment shaderprecision mediump float;void main(void){gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);};6.4.1 Adding vertex coloringThe vertex shader can define a varying col and use it to pass the interpolated vertex color, COLOR,to the fragment shader. The varying col variable is shared with the fragment shader. SeeExample 6-14:Example 6-14 Vertex shader passes interpolated color to fragment shaderattribute vec4 POSITION;attribute vec4 COLOR;varying vec4 col;void main(void){col = COLOR;gl_Position = POSITION;};Example 6-15 shows that the actual assignment to the gl_FragColor global color variable is donein the fragment shader:Example 6-15 Assignment of the color in the fragment shaderprecision mediump float;varying vec4 col;void main(void)ARM DUI 0527A-02a Copyright © 2010 ARM. All rights reserved. 6-12ID070710Non-Confidential - Draft - Beta