Mali GPU User Interface Engine Application Development Guide

Tutorial on Constructing Custom ShadersExample 6-24 Transformations in the draw loop...// execute the draw loopglEnable(GL_DEPTH_TEST);do{// use the keyboard to change the imageif (keyboard->getSpecialKeyState(Keyboard::KEY_SPACE)){// Rotate cameraif (keyboard->getSpecialKeyState(Keyboard::KEY_LEFT)){// Move camera (by rotating it) to create a new camera anglecamPos = calculateCamPos(4.0f, ++cameraAngle);// create a transformation matrix based on the new relationship// camera has changed, so view must be updatedview = mat4::lookAt(camPos, camTarget, upVector);}...}else{// Rotate objectif (keyboard->getSpecialKeyState(Keyboard::KEY_RIGHT)){// rotate the object itself about the specified vector// this changes object orientation, but camera does not moveworld *= mat4::rotation(1.0f, vec3(0.0f, 1.0f, 0.0f));}...}// calculate a new world view projection based on the camera, view, and// the world containing the objectwvpMatrix = proj * view * world;// pass the calculated matrix as a uniform to the vertex shader// the first parameter is the name of the uniform variable// the second parameter is the actual matrix datacontext->setUniformMatrix("WORLD_VIEW_PROJECTION", wvpMatrix);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);}// Draw the objectcontext->drawArrays(GL_TRIANGLE_STRIP, 0, 2);...}while ( context->update() );The vertex shader code in Example 6-25 calculates the position of a fragment based on theinterpolated POSITION value and the WORLD_VIEW_PROJECTION uniform:Example 6-25 Simple world view projection calculation in vertex shaderattribute vec4 POSITION;// position of a point on the primitive shapeattribute vec4 COLOR;// interpolated color from vertex colorsuniform mat4 WORLD_VIEW_PROJECTION; // transformation matrix passed as a uniformvarying vec4 vColor// parameter to pass to the fragment shaderARM DUI 0527A-02a Copyright © 2010 ARM. All rights reserved. 6-19ID070710Non-Confidential - Draft - Beta