Android NDK OpenGLES not rendering triangles - c++

Question

I have been struggling to correctly render any geometry using OpenGLES 1.0, 2.0, or 3.0 techniques. My testing device is a Samsung Galaxy S7 Edge (running Android 7.0). I have implemented numerous guides for both OpenGLES and EGL such as:
https://www.khronos.org/registry/EGL/sdk/docs/man/html/
https://www.khronos.org/assets/uploads/books/openglr_es_20_programming_guide_sample.pdf
http://www.ikerhurtado.com/egl-use-android-native-opengles-applications
The code was initially adapted from the "native-activity" example:
https://github.com/googlesamples/android-ndk/tree/master/native-activity
Android Manifest: (mostly from native-activity example)
...
<!-- Tell the system this app requires OpenGL ES 3.0. -->
<uses-feature android:glEsVersion="0x00030000" android:required="true" />
...
CMAKE: (mostly from native-activity example)
...
add_library(
native-activity
SHARED
main.cpp)
target_include_directories(
native-activity
PRIVATE
${ANDROID_NDK}/sources/android/native_app_glue)
# add lib dependencies
target_link_libraries(
native-activity
android
native_app_glue
EGL
GLESv3
log)
...
main.cpp: (mostly from native-activity example, cropped for relevance)
...
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <GLES3/gl3.h>
#include <GLES3/gl3ext.h>
#include <android_native_app_glue.h>
...
/*
*Test GLES 1.0, should draw a white triangle on red background
*/
class TestGLES10 {
public:
GLuint program;
void create() {
char vssource[] =
"attribute vec4 vertexPosition; \n"
"void main(){ \n"
" gl_Position = vertexPosition; \n"
"} \n";
char fssource[] =
"precision mediump float; \n"
"void main(){ \n"
" gl_FragColor = vec4(1.0); "
"} \n";
auto compile = [](const char *source, GLenum type){
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, &source, nullptr);
glCompileShader(shader);
return shader;
};
GLuint vs = compile(string(vssource).c_str(), GL_VERTEX_SHADER);
GLuint fs = compile(string(fssource).c_str(), GL_FRAGMENT_SHADER);
program = glCreateProgram();
glAttachShader(program, vs);
glAttachShader(program, fs);
glBindAttribLocation(program, 0, "vertexPosition");
glLinkProgram(program);
glDisable(GL_DEPTH_TEST);
}
void update() {
glClearColor(1,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
float positions[]{
0.0f, 0.1f,
-0.1f, -0.1f,
0.1f, -0.1f
};
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, positions);
glEnableVertexAttribArray(0);
glDrawArrays(GL_TRIANGLES, 0, 3);
}
};
/*
*Test GLES 3.0, should draw a white triangle on blue background
*/
class TestGLES30 {
public:
GLuint vbo, vao, program;
void create() {
char vssource[] =
"#version 300 es\n"
"layout(location=0) in vec4 vertexPosition; \n"
"void main(){ \n"
" gl_Position = vertexPosition; \n"
"} \n";
char fssource[] =
"#version 300 es\n"
"precision mediump float; \n"
"out vec4 fragment; \n"
"void main(){ \n"
" fragment = vec4(1.0); "
"} \n";
auto compile = [](const char *source, GLenum type){
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, &source, nullptr);
glCompileShader(shader);
return shader;
};
GLuint vs = compile(string(vssource).c_str(), GL_VERTEX_SHADER);
GLuint fs = compile(string(fssource).c_str(), GL_FRAGMENT_SHADER);
program = glCreateProgram();
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
float positions[]{
0.0f, 0.5f,
-0.5f, -0.5f,
0.5f, -0.5f
};
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, 2*4, positions, GL_STATIC_DRAW);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2*4, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
void update() {
glClearColor(0,0,1,1);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
}
};
...
void android_main(android_app* appInterface) {
appInterface->onAppCmd = commandRelay;
appInterface->onInputEvent = inputRelay;
while(appInterface->window == nullptr){
pollEvents(appInterface);
}
EGLDisplay display;
EGLSurface surface;
EGLContext context;
EGLint majorVersion, minorVersion;
EGLConfig config;
EGLint width, height;
EGLint nativeVisualID;
EGLint configCount;
display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
assert(display != EGL_NO_DISPLAY);
eglInitialize(display, &majorVersion, &minorVersion);
//https://www.khronos.org/registry/EGL/sdk/docs/man/html/eglChooseConfig.xhtml
const EGLint displayAttrib[] = {
EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,//egl 1.3 req
EGL_NATIVE_RENDERABLE, EGL_TRUE,
EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
EGL_BLUE_SIZE, 8,
EGL_GREEN_SIZE, 8,
EGL_RED_SIZE, 8,
EGL_NONE
};
//retreive configs
eglChooseConfig(display, displayAttrib, 0, 0, &configCount);
std::unique_ptr<EGLConfig[]> supported(new EGLConfig[configCount]);
eglChooseConfig(display, displayAttrib, supported.get(), configCount, &configCount);
EGLint i = 0, v;
for (; i < configCount; i++) {
auto get = [&](EGLint attrib){
eglGetConfigAttrib(display, supported[i], attrib, &v);
return v;
};
if (Math2::equal(8,
get(EGL_RED_SIZE),
get(EGL_GREEN_SIZE),
get(EGL_BLUE_SIZE),
get(EGL_DEPTH_SIZE))) {//expands to 8 == get(EGL_RED_SIZE) == ...
config = supported[i];
break;
}
}
if (i == configCount) {//default to first
config = supported[0];
}
const EGLint surfaceAttrib[] = {
EGL_RENDER_BUFFER, EGL_BACK_BUFFER,// render to the back buffer, egl 1.2 req
EGL_NONE
};
eglGetConfigAttrib(display, config, EGL_NATIVE_VISUAL_ID, &nativeVisualID);
surface = eglCreateWindowSurface(display, config, appInterface->window, surfaceAttrib);
const EGLint contextAttrib[] = {
EGL_CONTEXT_CLIENT_VERSION, 2,// request a context using Open GL ES 2.0
EGL_NONE
};
context = eglCreateContext(display, config, EGL_NO_CONTEXT, contextAttrib);
assert(context != EGL_NO_CONTEXT);
//sets initial viewport and scissor dimensions to draw surface size
eglMakeCurrent(display, surface, surface, context);
eglQuerySurface(display, surface, EGL_WIDTH, &width);
eglQuerySurface(display, surface, EGL_HEIGHT, &height);
//this call was mentioned, but missing from the example (removing has same effect)
ANativeWindow_setBuffersGeometry(appInterface->window, width, height, nativeVisualID);
TestGLES10 test;
test.create();
while (true){
test.update();
eglSwapBuffers(display, surface);
}
}
Results:
Logged Info:
Vendor : Qualcomm
Renderer : Adreno (TM) 530
Version : OpenGL ES 3.2 V#145.0 (GIT#I86b60582e4)
EGL version : 1.4
Window dimensions : 1080, 1920
Additionally, the device has resolution scaling set to 1080x1920.
Test 1.0: https://i.imgur.com/dmofGYw.png
Test 3.0: https://i.imgur.com/uoghOZc.png
According to:
https://www.khronos.org/registry/EGL/sdk/docs/man/html/eglMakeCurrent.xhtml
the glViewPort should have been initialized to the surface size (1080x1920), so I am at a loss for how the white rectangle could occur.
The shader code for both tests compile without errors from Adreno.
Why wont it render geometry correctly?
According to :
https://www.khronos.org/registry/EGL/sdk/docs/man/html/eglCreateContext.xhtml
there is no way to specifically request a 3.0 or higher context, why does the created context have version 3.2 when I can only request 2.0?

Answer 1

Why wont it render geometry correctly?
Your position arrays are three vertices of two compoenents each (x, y), but you're telling GL they have three components each:
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, positions);
why does the created context have version 3.2 when I can only request 2.0?
Versions 3.x are entirely forward compatible with code written for version 2.0, so it's legal for the drivers just to up-convert a context to the newest version they support.