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      1 // OpenGL ES 2.0 code
      2 
      3 #include <nativehelper/jni.h>
      4 #define LOG_TAG "GL2JNI gl_code.cpp"
      5 #include <utils/Log.h>
      6 
      7 #include <EGL/egl.h>
      8 #include <GLES2/gl2.h>
      9 #include <GLES2/gl2ext.h>
     10 
     11 #include <stdio.h>
     12 #include <stdlib.h>
     13 #include <math.h>
     14 
     15 static void printGLString(const char *name, GLenum s) {
     16     const char *v = (const char *) glGetString(s);
     17     ALOGI("GL %s = %s\n", name, v);
     18 }
     19 
     20 static void checkGlError(const char* op) {
     21     for (GLint error = glGetError(); error; error
     22             = glGetError()) {
     23         ALOGI("after %s() glError (0x%x)\n", op, error);
     24     }
     25 }
     26 
     27 static const char gVertexShader[] = "attribute vec4 vPosition;\n"
     28     "void main() {\n"
     29     "  gl_Position = vPosition;\n"
     30     "}\n";
     31 
     32 static const char gFragmentShader[] = "precision mediump float;\n"
     33     "void main() {\n"
     34     "  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);\n"
     35     "}\n";
     36 
     37 GLuint loadShader(GLenum shaderType, const char* pSource) {
     38     GLuint shader = glCreateShader(shaderType);
     39     if (shader) {
     40         glShaderSource(shader, 1, &pSource, NULL);
     41         glCompileShader(shader);
     42         GLint compiled = 0;
     43         glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
     44         if (!compiled) {
     45             GLint infoLen = 0;
     46             glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
     47             if (infoLen) {
     48                 char* buf = (char*) malloc(infoLen);
     49                 if (buf) {
     50                     glGetShaderInfoLog(shader, infoLen, NULL, buf);
     51                     ALOGE("Could not compile shader %d:\n%s\n",
     52                             shaderType, buf);
     53                     free(buf);
     54                 }
     55                 glDeleteShader(shader);
     56                 shader = 0;
     57             }
     58         }
     59     }
     60     return shader;
     61 }
     62 
     63 GLuint createProgram(const char* pVertexSource, const char* pFragmentSource) {
     64     GLuint vertexShader = loadShader(GL_VERTEX_SHADER, pVertexSource);
     65     if (!vertexShader) {
     66         return 0;
     67     }
     68 
     69     GLuint pixelShader = loadShader(GL_FRAGMENT_SHADER, pFragmentSource);
     70     if (!pixelShader) {
     71         return 0;
     72     }
     73 
     74     GLuint program = glCreateProgram();
     75     if (program) {
     76         glAttachShader(program, vertexShader);
     77         checkGlError("glAttachShader");
     78         glAttachShader(program, pixelShader);
     79         checkGlError("glAttachShader");
     80         glLinkProgram(program);
     81         GLint linkStatus = GL_FALSE;
     82         glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
     83         if (linkStatus != GL_TRUE) {
     84             GLint bufLength = 0;
     85             glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
     86             if (bufLength) {
     87                 char* buf = (char*) malloc(bufLength);
     88                 if (buf) {
     89                     glGetProgramInfoLog(program, bufLength, NULL, buf);
     90                     ALOGE("Could not link program:\n%s\n", buf);
     91                     free(buf);
     92                 }
     93             }
     94             glDeleteProgram(program);
     95             program = 0;
     96         }
     97     }
     98     return program;
     99 }
    100 
    101 GLuint gProgram;
    102 GLuint gvPositionHandle;
    103 
    104 bool setupGraphics(int w, int h) {
    105     printGLString("Version", GL_VERSION);
    106     printGLString("Vendor", GL_VENDOR);
    107     printGLString("Renderer", GL_RENDERER);
    108     printGLString("Extensions", GL_EXTENSIONS);
    109 
    110     ALOGI("setupGraphics(%d, %d)", w, h);
    111     gProgram = createProgram(gVertexShader, gFragmentShader);
    112     if (!gProgram) {
    113         ALOGE("Could not create program.");
    114         return false;
    115     }
    116     gvPositionHandle = glGetAttribLocation(gProgram, "vPosition");
    117     checkGlError("glGetAttribLocation");
    118     ALOGI("glGetAttribLocation(\"vPosition\") = %d\n",
    119             gvPositionHandle);
    120 
    121     glViewport(0, 0, w, h);
    122     checkGlError("glViewport");
    123     return true;
    124 }
    125 
    126 const GLfloat gTriangleVertices[] = { 0.0f, 0.5f, -0.5f, -0.5f,
    127         0.5f, -0.5f };
    128 
    129 void renderFrame() {
    130     static float grey;
    131     grey += 0.01f;
    132     if (grey > 1.0f) {
    133         grey = 0.0f;
    134     }
    135     glClearColor(grey, grey, grey, 1.0f);
    136     checkGlError("glClearColor");
    137     glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    138     checkGlError("glClear");
    139 
    140     glUseProgram(gProgram);
    141     checkGlError("glUseProgram");
    142 
    143     glVertexAttribPointer(gvPositionHandle, 2, GL_FLOAT, GL_FALSE, 0, gTriangleVertices);
    144     checkGlError("glVertexAttribPointer");
    145     glEnableVertexAttribArray(gvPositionHandle);
    146     checkGlError("glEnableVertexAttribArray");
    147     glDrawArrays(GL_TRIANGLES, 0, 3);
    148     checkGlError("glDrawArrays");
    149 }
    150 
    151 extern "C" {
    152     JNIEXPORT void JNICALL Java_com_android_gl2jni_GL2JNILib_init(JNIEnv * env, jobject obj,  jint width, jint height);
    153     JNIEXPORT void JNICALL Java_com_android_gl2jni_GL2JNILib_step(JNIEnv * env, jobject obj);
    154 };
    155 
    156 JNIEXPORT void JNICALL Java_com_android_gl2jni_GL2JNILib_init(JNIEnv * env, jobject obj,  jint width, jint height)
    157 {
    158     setupGraphics(width, height);
    159 }
    160 
    161 JNIEXPORT void JNICALL Java_com_android_gl2jni_GL2JNILib_step(JNIEnv * env, jobject obj)
    162 {
    163     renderFrame();
    164 }
    165 
    166