Mali GPU User Interface Engine Application Development Guide

Tutorial on Constructing Custom ShadersLighting calculation in the vertex shaderThe vertex shader code in Example 6-27 calculates the position of a fragment based on theinterpolated POSITION and lighting vectors from the transformations:Example 6-27 Specular lighting calculation in vertex shaderuniform mat4 WORLD_VIEW_PROJECTION;uniform mat3 WORLD;// the light at each location depends on the relative angles between light position,point location, camera angle, and lighting colorsuniform vec3 LIGHT_POSITION;uniform vec3 CAMERA_POSITION;uniform vec3 DIFFUSE_LIGHT;uniform vec3 SPECULAR_LIGHT;// interpolated values for this point on primitive shapeattribute vec4 POSITION;attribute vec3 NORMAL;// light values to pass to fragment shadervarying vec3 vDiffuse;varying vec3 vSpecular;void main(void){// calculate the position based on the transformationgl_Position = WORLD_VIEW_PROJECTION * POSITION;// vector variables used to calculate lightingvec3 normal = normalize(WORLD * NORMAL);vec3 pos = WORLD * POSITION.xyz;// determine the angle from the light to the shape positionvec3 lightVector = normalize(LIGHT_POSITION - pos);// calculate a multiplier for the diffuse lightfloat nDotL = max(dot(normal, lightVector), 0.0);vDiffuse = DIFFUSE_LIGHT * nDotL;}// No point in calculating specular reflections from the backside of vertices.float specPow = 0.0;if (nDotL > 0.0){normalize the camera position and calculate the light reflectionvec3 cameraVector = normalize(CAMERA_POSITION - pos);vec3 reflectVector = reflect(-cameraVector, normal);// determine the amount of reflected lightspecPow = pow(max(dot(reflectVector, lightVector), 0.0), 4.0);}// assign the specular light based on the specular uniform and// the computed multipliervSpecular = SPECULAR_LIGHT * specPow;As shown in Example 6-28, the fragment shader simply combines the light sources:Example 6-28 Fragment shader adds specular light to background lightuniform vec3 AMBIENT_LIGHT;uniform vec4 COLOR;varying vec3 vDiffuse; // calculated diffuse componentvarying vec3 vSpecular; // calculated specular component based on light positionARM DUI 0527A-02a Copyright © 2010 ARM. All rights reserved. 6-21ID070710Non-Confidential - Draft - Beta