Triangle.java Source code

Introduction

Here is the source code for Triangle.java

Source

import android.opengl.GLES20;

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

public class Triangle {

    private int mMVPMatrixHandle;

    private final String vertexShaderCode = "attribute vec4 vPosition;" + "uniform mat4 uMVPMatrix;"
            + "void main() {" + "  gl_Position = uMVPMatrix * vPosition;" + "}";

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

    final int COORDS_PER_VERTEX = 3;
    float triangleCoords[] = { 0.0f, 0.66f, 0.0f, -0.5f, -0.33f, 0.0f, 0.5f, -0.33f, 0.0f };

    float color[] = { 0.63f, 0.76f, 0.22f, 1.0f };

    private final int mProgram;
    private FloatBuffer vertexBuffer;
    private int mPositionHandle;
    private int mColorHandle;
    private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX;
    private final int vertexStride = COORDS_PER_VERTEX * 4;

    public int loadShader(int type, String shaderCode) {
        int shader = GLES20.glCreateShader(type);
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);
        return shader;
    }

    public Triangle() {
        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
        int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
        mProgram = GLES20.glCreateProgram();
        GLES20.glAttachShader(mProgram, vertexShader);
        GLES20.glAttachShader(mProgram, fragmentShader);
        GLES20.glLinkProgram(mProgram);

        ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
        bb.order(ByteOrder.nativeOrder());

        vertexBuffer = bb.asFloatBuffer();
        vertexBuffer.put(triangleCoords);
        vertexBuffer.position(0);
    }

    public void draw(float[] mvpMatrix) {
        GLES20.glUseProgram(mProgram);
        mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        GLES20.glEnableVertexAttribArray(mPositionHandle);
        GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride,
                vertexBuffer);
        mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
        GLES20.glUniform4fv(mColorHandle, 1, color, 0);

        mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
        GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);

        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
        GLES20.glDisableVertexAttribArray(mPositionHandle);
    }

}