[실시간 운영체제] Computer graphics (Draw Triangle)

Open GL의 기본적인 코드는

https://developer.android.com/develop/ui/views/graphics/opengl

위 사이트에 공개된 코드를 사용하였다.

---

 

 

Mainactivity.java

package com.example.computer_graphics;

import androidx.appcompat.app.AppCompatActivity;

import android.opengl.GLSurfaceView;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    private GLSurfaceView gLView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create a GLSurfaceView instance and set it
        // as the ContentView for this Activity.
        gLView = new MyGLSurfaceView(this);
        setContentView(gLView);
    }
}

 

 

 

MyGLSurfaceView.java

package com.example.computer_graphics;

import android.content.Context;
import android.opengl.GLSurfaceView;

class MyGLSurfaceView extends GLSurfaceView {

    private final MyGLRenderer renderer;

    public MyGLSurfaceView(Context context){
        super(context);

        // Create an OpenGL ES 2.0 context
        setEGLContextClientVersion(2);

        renderer = new MyGLRenderer();

        // Set the Renderer for drawing on the GLSurfaceView
        setRenderer(renderer);
    }
}

 

 

MyGLRenderer.java

package com.example.computer_graphics;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.opengl.Matrix;

public class MyGLRenderer implements GLSurfaceView.Renderer {

    private Triangle mTriangle;

    private final float[] vPMatrix = new float[16];
    private final float[] projectionMatrix = new float[16];
    private final float[] viewMatrix = new float[16];

    public void onSurfaceCreated(GL10 unused, EGLConfig config) {
        // Set the background frame color
        GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        mTriangle = new Triangle();
    }

    public void onDrawFrame(GL10 unused) {
        // Redraw background color
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);

        // Set the camera position (View matrix)
        Matrix.setLookAtM(viewMatrix, 0, 0, 0, 3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

        // Calculate the projection and view transformation
        Matrix.multiplyMM(vPMatrix, 0, projectionMatrix, 0, viewMatrix, 0);

        mTriangle.draw(vPMatrix);


    }

    public void onSurfaceChanged(GL10 unused, int width, int height) {
        GLES20.glViewport(0, 0, width, height);

        float ratio = (float) width / height;

        // this projection matrix is applied to object coordinates
        // in the onDrawFrame() method
        Matrix.frustumM(projectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
    }

    public static int loadShader(int type, String shaderCode){

        // create a vertex shader type (GLES20.GL_VERTEX_SHADER)
        // or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
        int shader = GLES20.glCreateShader(type);

        // add the source code to the shader and compile it
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);

        return shader;
    }
}

 

Triangle.java

package com.example.computer_graphics;

import android.opengl.GLES20;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;


public class Triangle {

    private final String vertexShaderCode =
            // This matrix member variable provides a hook to manipulate
            // the coordinates of the objects that use this vertex shader
            "uniform mat4 uMVPMatrix;" +
                    "attribute vec4 vPosition;" +
                    "void main() {" +
                    // the matrix must be included as a modifier of gl_Position
                    // Note that the uMVPMatrix factor *must be first* in order
                    // for the matrix multiplication product to be correct.
                    "  gl_Position = uMVPMatrix * vPosition;" +
                    "}";

    private int vPMatrixHandle;

    private FloatBuffer vertexBuffer;

    private final int mProgram;
    
    private int positionHandle;
    private int colorHandle;

    private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX;
    private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex

    // number of coordinates per vertex in this array
    static final int COORDS_PER_VERTEX = 3;
    static float triangleCoords[] = {   // in counterclockwise order:
            0.0f,  0.622008459f, 0.0f, // top
            -0.5f, -0.311004243f, 0.0f, // bottom left
            0.5f, -0.311004243f, 0.0f  // bottom right
    };

    // Set color with red, green, blue and alpha (opacity) values
    //float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };

    //색 빨강으로 바꾸기
    float color[] = { 1.0f, 0.0f, 0.0f, 1.0f };

    public Triangle() {
        // initialize vertex byte buffer for shape coordinates
        ByteBuffer bb = ByteBuffer.allocateDirect(
                // (number of coordinate values * 4 bytes per float)
                triangleCoords.length * 4);
        // use the device hardware's native byte order
        bb.order(ByteOrder.nativeOrder());

        // create a floating point buffer from the ByteBuffer
        vertexBuffer = bb.asFloatBuffer();
        // add the coordinates to the FloatBuffer
        vertexBuffer.put(triangleCoords);
        // set the buffer to read the first coordinate
        vertexBuffer.position(0);

        int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER,
                vertexShaderCode);
        int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER,
                fragmentShaderCode);

        // create empty OpenGL ES Program
        mProgram = GLES20.glCreateProgram();

        // add the vertex shader to program
        GLES20.glAttachShader(mProgram, vertexShader);

        // add the fragment shader to program
        GLES20.glAttachShader(mProgram, fragmentShader);

        // creates OpenGL ES program executables
        GLES20.glLinkProgram(mProgram);
    }

    public void draw(float[] mvpMatrix) {

        // get handle to shape's transformation matrix
        vPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");

        // Pass the projection and view transformation to the shader
        GLES20.glUniformMatrix4fv(vPMatrixHandle, 1, false, mvpMatrix, 0);

        // Add program to OpenGL ES environment
        GLES20.glUseProgram(mProgram);

        // get handle to vertex shader's vPosition member
        positionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");

        // Enable a handle to the triangle vertices
        GLES20.glEnableVertexAttribArray(positionHandle);

        // Prepare the triangle coordinate data
        GLES20.glVertexAttribPointer(positionHandle, COORDS_PER_VERTEX,
                GLES20.GL_FLOAT, false,
                vertexStride, vertexBuffer);

        // get handle to fragment shader's vColor member
        colorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");

        // Set color for drawing the triangle
        GLES20.glUniform4fv(colorHandle, 1, color, 0);

        // Draw the triangle
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);

        // Disable vertex array
        GLES20.glDisableVertexAttribArray(positionHandle);

    }

    private final String fragmentShaderCode =
            "precision mediump float;" +
                    "uniform vec4 vColor;" +
                    "void main() {" +
                    "  gl_FragColor = vColor;" +
                    "}";

}

 

 

 

 

원하는 삼각형의 좌표를 변경해주면 다양한 모양의 삼각형을 만들 수 있다.

static float triangleCoords[] = {   // in counterclockwise order:
        -0.5f,  0.622008459f, 0.0f, // top
        -0.5f, -0.311004243f, 0.0f, // bottom left
        0.5f, -0.311004243f, 0.0f  // bottom right
};