How to color individual pixels with OpenGL ES 2.0? - opengl-es-2.0

Question

Is there possible to change the color of an individual pixel with OpenGL ES 2.0? Right now, I have found that I can manage that using a vertex. I've used this method to draw it:
GLES20.glDrawArrays(GLES20.GL_POINTS, 0, 1);
The size of the point was set to minimum in order to be a single pixel painted.
All good, until I've needed to draw 3 to 4 millions of them! It takes 5-6 seconds to initialize only one frame. This is time-inefficient as long as the pixels will be updated constantly. The update/ refresh would be preferable to be as close as possible to 60 fps.
How can I paint them in a more efficient way?
Note: It's a must to paint them individually only!
My attempt is here (for a screen of 1440x2560 px):
package com.example.ctelescu.opengl_pixel_draw;
import android.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.opengl.Matrix;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
public class PixelDrawRenderer implements GLSurfaceView.Renderer {
private float[] mModelMatrix = new float[16];
private float[] mViewMatrix = new float[16];
private float[] mProjectionMatrix = new float[16];
private float[] mMVPMatrix = new float[16];
private final FloatBuffer mVerticesBuffer;
private int mMVPMatrixHandle;
private int mPositionHandle;
private int mColorHandle;
private final int mBytesPerFloat = 4;
private final int mStrideBytes = 7 * mBytesPerFloat;
private final int mPositionOffset = 0;
private final int mPositionDataSize = 3;
private final int mColorOffset = 3;
private final int mColorDataSize = 4;
public PixelDrawRenderer() {
// Define the vertices.
// final float[] vertices = {
// // X, Y, Z,
// // R, G, B, A
// -1f, 1f, 0.0f,
// 1.0f, 0.0f, 0.0f, 1.0f,
//
// -0.9f, 1.2f, 0.0f,
// 0.0f, 0.0f, 1.0f, 1.0f,
//
// -0.88f, 1.2f, 0.0f,
// 0.0f, 1.0f, 0.0f, 1.0f,
//
// -0.87f, 1.2f, 0.0f,
// 0.0f, 1.0f, 0.0f, 1.0f,
//
// -0.86f, 1.2f, 0.0f,
// 0.0f, 1.0f, 0.0f, 1.0f,
//
// -0.85f, 1.2f, 0.0f,
// 0.0f, 1.0f, 0.0f, 1.0f};
// Initialize the buffers.
mVerticesBuffer = ByteBuffer.allocateDirect(22579200 * mBytesPerFloat)
.order(ByteOrder.nativeOrder()).asFloatBuffer();
// mVerticesBuffer.put(vertices);
}
#Override
public void onSurfaceCreated(GL10 glUnused, EGLConfig config) {
// Set the background clear color to gray.
GLES20.glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
// Position the eye behind the origin.
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 1.5f;
// We are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -5.0f;
// Set our up vector. This is where our head would be pointing were we holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;
// Set the view matrix. This matrix can be said to represent the camera position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);
final String vertexShader =
"uniform mat4 u_MVPMatrix; \n" // A constant representing the combined model/view/projection matrix.
+ "attribute vec4 a_Position; \n" // Per-vertex position information we will pass in.
+ "attribute vec4 a_Color; \n" // Per-vertex color information we will pass in.
+ "varying vec4 v_Color; \n" // This will be passed into the fragment shader.
+ "void main() \n" // The entry point for our vertex shader.
+ "{ \n"
+ " v_Color = a_Color; \n" // Pass the color through to the fragment shader.
// It will be interpolated across the vertex.
+ " gl_Position = u_MVPMatrix \n" // gl_Position is a special variable used to store the final position.
+ " * a_Position; \n" // Multiply the vertex by the matrix to get the final point in
+ " gl_PointSize = 0.1; \n"
+ "} \n"; // normalized screen coordinates.
final String fragmentShader =
"#ifdef GL_FRAGMENT_PRECISION_HIGH \n"
+ "precision highp float; \n"
+ "#else \n"
+ "precision mediump float; \n" // Set the default precision to medium. We don't need as high of a
// precision in the fragment shader.
+ "#endif \n"
+ "varying vec4 v_Color; \n" // This is the color from the vertex shader interpolated across the
// vertex per fragment.
+ "void main() \n" // The entry point for our fragment shader.
+ "{ \n"
+ " gl_FragColor = v_Color; \n" // Pass the color directly through the pipeline.
+ "} \n";
// Load in the vertex shader.
int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if (vertexShaderHandle != 0) {
// Pass in the shader source.
GLES20.glShaderSource(vertexShaderHandle, vertexShader);
// Compile the shader.
GLES20.glCompileShader(vertexShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0) {
GLES20.glDeleteShader(vertexShaderHandle);
vertexShaderHandle = 0;
}
}
if (vertexShaderHandle == 0) {
throw new RuntimeException("Error creating vertex shader.");
}
// Load in the fragment shader shader.
int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if (fragmentShaderHandle != 0) {
// Pass in the shader source.
GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
// Compile the shader.
GLES20.glCompileShader(fragmentShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0) {
GLES20.glDeleteShader(fragmentShaderHandle);
fragmentShaderHandle = 0;
}
}
if (fragmentShaderHandle == 0) {
throw new RuntimeException("Error creating fragment shader.");
}
// Create a program object and store the handle to it.
int programHandle = GLES20.glCreateProgram();
if (programHandle != 0) {
// Bind the vertex shader to the program.
GLES20.glAttachShader(programHandle, vertexShaderHandle);
// Bind the fragment shader to the program.
GLES20.glAttachShader(programHandle, fragmentShaderHandle);
// Bind attributes
GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
GLES20.glBindAttribLocation(programHandle, 1, "a_Color");
// Link the two shaders together into a program.
GLES20.glLinkProgram(programHandle);
// Get the link status.
final int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
// If the link failed, delete the program.
if (linkStatus[0] == 0) {
GLES20.glDeleteProgram(programHandle);
programHandle = 0;
}
}
if (programHandle == 0) {
throw new RuntimeException("Error creating program.");
}
// Set program handles. These will later be used to pass in values to the program.
mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");
// Tell OpenGL to use this program when rendering.
GLES20.glUseProgram(programHandle);
}
#Override
public void onSurfaceChanged(GL10 glUnused, int width, int height) {
// Set the OpenGL viewport to the same size as the surface.
GLES20.glViewport(0, 0, width, height);
// Create a new perspective projection matrix. The height will stay the same
// while the width will vary as per aspect ratio.
final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 10.0f;
Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);
float[] vertices = new float[22579200];
int counter = 0;
for (float i = -width / 2; i < width / 2; i++) {
for (float j = height / 2; j > -height / 2; j--) {
// Initialize the buffers.
vertices[counter++] = 2f * i * (1f / width); //X
vertices[counter++] = 2f * j * (1.5f / height); //Y
vertices[counter++] = 0; //Z
vertices[counter++] = 1f; //blue
vertices[counter++] = 1f; //green
vertices[counter++] = 0f; //blue
vertices[counter++] = 1f; //alpha
}
}
mVerticesBuffer.put(vertices);
mVerticesBuffer.clear();
}
#Override
public void onDrawFrame(GL10 glUnused) {
GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
// Draw the vertices facing straight on.
Matrix.setIdentityM(mModelMatrix, 0);
drawVertices(mVerticesBuffer);
}
private void drawVertices(final FloatBuffer aVertexBuffer) {
// Pass in the position information
aVertexBuffer.position(mPositionOffset);
GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aVertexBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Pass in the color information
aVertexBuffer.position(mColorOffset);
GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aVertexBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);
// This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
// (which currently contains model * view).
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
// This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
// (which now contains model * view * projection).
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_POINTS, 0, 3225600);
}
}