atlas book skeleton by Unknown

Author:Unknown
Language: eng
Format: mobi, epub

Helper utilities and other features

A utility class is one that contains miscellaneous helper methods that do not concretely fit into any other class. In essence, it is a random collection of useful things. Glitcher VR has one such class, aptly named Glitcher_Utils, that contains methods to compile shader programs, and save and load preferences between application launches.

There isn’t anything particularly special about this class, but since it is handy and generic enough to be used in any graphical project (with slight modification), I will reproduce the code here:

public class Glitcher_Utils { public static final String LOG_TAG="glitcher_log"; public static final int V_SHADE=0, F_SHADE=1, S_PROG=2; public static final String SAVE_SHARED_FILENAME="net.dystopiazero.theglitcher.sharedprefs"; public static final String SAVE_LAST_EFFECT="last_effect"; public static final String SAVE_LAST_MODE="last_mode"; public static final String SAVE_LAST_CAM_INDEX="last_cam_index"; public static void savePreference(String tag, String val, Context context) { SharedPreferences prefs=context.getSharedPreferences(SAVE_SHARED_FILENAME,Context.MODE_PRIVATE); SharedPreferences.Editor editor=prefs.edit(); editor.putString(tag, val); editor.commit(); } public static String getPreference(String tag, Context context) { SharedPreferences prefs=context.getSharedPreferences(SAVE_SHARED_FILENAME,Context.MODE_PRIVATE); String val=prefs.getString(tag, "null"); return val; } public static boolean compileShaders(String vertex_shader, String fragment_shader, int[] ids) { if (ids.length<3) { Log.e(LOG_TAG,"Glitcher_Utils,compileShaders: Buffer too small"); return false; } ids[V_SHADE]=GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER); ids[F_SHADE]=GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER); GLES20.glShaderSource(ids[V_SHADE],vertex_shader); GLES20.glShaderSource(ids[F_SHADE],fragment_shader); GLES20.glCompileShader(ids[V_SHADE]); GLES20.glCompileShader(ids[F_SHADE]); int[] info=new int[1]; GLES20.glGetShaderiv(ids[V_SHADE], GLES20.GL_COMPILE_STATUS, info,0); if (info[0]==0) { Log.e(Glitcher_Utils.LOG_TAG,"Glitcher_Utils,compileShaders: Vertex Shader Error: "+GLES20.glGetShaderInfoLog(ids[V_SHADE])); GLES20.glDeleteShader(ids[V_SHADE]); return false; } GLES20.glGetShaderiv(ids[F_SHADE], GLES20.GL_COMPILE_STATUS, info,0); if (info[0]==0) { Log.e(Glitcher_Utils.LOG_TAG,"Glitcher_Utils,compileShaders: Fragment Shader Error: "+GLES20.glGetShaderInfoLog(ids[F_SHADE])); GLES20.glDeleteShader(ids[F_SHADE]); return false; } ids[S_PROG]=GLES20.glCreateProgram(); GLES20.glAttachShader(ids[S_PROG],ids[V_SHADE]); GLES20.glAttachShader(ids[S_PROG],ids[F_SHADE]); GLES20.glLinkProgram(ids[S_PROG]); IntBuffer inf=IntBuffer.wrap(info); GLES20.glGetProgramiv(ids[S_PROG], GLES20.GL_LINK_STATUS, inf); if (info[0]==GLES20.GL_FALSE) { Log.e(Glitcher_Utils.LOG_TAG,"Glitcher_Utils,compileShaders: Shader Program Link Error: "+GLES20.glGetProgramInfoLog(ids[S_PROG])); GLES20.glDeleteProgram(ids[S_PROG]); return false; } return true; } }

The savePreference() and getPreference() methods save and retrieve a String value using Android’s SharedPreferences class, which can be used to save data between application launches. In Glitcher VR, these methods are used to save information about the active filter, active camera, and whether VR mode is enabled on program exit. On program startup, the preferences are retrieved and the previously active effect is selected, the previously active camera is opened, and VR mode is appropriately toggled.

Likewise, the static compileShaders() method compiles a vertex and fragment shader, links them to a shader program, and places their identifiers in an array that is supplied by the caller. This method is called at least once from every filter, and used in other parts of Glitcher VR that require things to be rendered to the screen, such as the notification system. As this method performs a common generic task, it can be plugged into any OpenGL program with minimal modification.

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