libgdx通過鼠標單擊繪制矩形

Question

我正在嘗試使用libgdx或與OpenGL更好的產品。 由於我的演講，我不得不處理Java。

我想繪制一個背景，可以在其中單擊鼠標，並在鼠標位置（單擊時）上繪制一個新的矩形。 因此，“舊”矩形必須留在那里。

到目前為止，這是我的代碼：

package com.ru.tgra.lab1;


import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;  
import com.badlogic.gdx.graphics.GL20;

import java.nio.FloatBuffer;

import com.badlogic.gdx.utils.BufferUtils;

public class Lab1Game extends ApplicationAdapter {

private FloatBuffer vertexBuffer;

private FloatBuffer modelMatrix;
private FloatBuffer projectionMatrix;

private int renderingProgramID;
private int vertexShaderID;
private int fragmentShaderID;

private int positionLoc;

private int modelMatrixLoc;
private int projectionMatrixLoc;

private int colorLoc;

private float position_x;
private float position_y;
private float size_rect = 100;

private int screenWidth;
private int screenHeight;


@Override
public void create () {

    String vertexShaderString;
    String fragmentShaderString;   

    vertexShaderString = Gdx.files.internal("shaders/simple2D.vert").readString();
    fragmentShaderString =  Gdx.files.internal("shaders/simple2D.frag").readString();

    vertexShaderID = Gdx.gl.glCreateShader(GL20.GL_VERTEX_SHADER);
    fragmentShaderID = Gdx.gl.glCreateShader(GL20.GL_FRAGMENT_SHADER);

    Gdx.gl.glShaderSource(vertexShaderID, vertexShaderString);
    Gdx.gl.glShaderSource(fragmentShaderID, fragmentShaderString);

    Gdx.gl.glCompileShader(vertexShaderID);
    Gdx.gl.glCompileShader(fragmentShaderID);

    renderingProgramID = Gdx.gl.glCreateProgram();

    Gdx.gl.glAttachShader(renderingProgramID, vertexShaderID);
    Gdx.gl.glAttachShader(renderingProgramID, fragmentShaderID);

    Gdx.gl.glLinkProgram(renderingProgramID);

    positionLoc             = Gdx.gl.glGetAttribLocation(renderingProgramID, "a_position");
    Gdx.gl.glEnableVertexAttribArray(positionLoc);

    modelMatrixLoc          = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_modelMatrix");
    projectionMatrixLoc = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_projectionMatrix");

    colorLoc                = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_color");

    Gdx.gl.glUseProgram(renderingProgramID);

    float[] pm = new float[16];

    pm[0] = 2.0f / Gdx.graphics.getWidth(); pm[4] = 0.0f; pm[8] = 0.0f; pm[12] = -1.0f;
    pm[1] = 0.0f; pm[5] = 2.0f / Gdx.graphics.getHeight(); pm[9] = 0.0f; pm[13] = -1.0f;
    pm[2] = 0.0f; pm[6] = 0.0f; pm[10] = 1.0f; pm[14] = 0.0f;
    pm[3] = 0.0f; pm[7] = 0.0f; pm[11] = 0.0f; pm[15] = 1.0f;

    projectionMatrix = BufferUtils.newFloatBuffer(16);
    projectionMatrix.put(pm);
    projectionMatrix.rewind();
    Gdx.gl.glUniformMatrix4fv(projectionMatrixLoc, 1, false, projectionMatrix);


    float[] mm = new float[16];

    mm[0] = 1.0f; mm[4] = 0.0f; mm[8] = 0.0f; mm[12] = 0.0f;
    mm[1] = 0.0f; mm[5] = 1.0f; mm[9] = 0.0f; mm[13] = 0.0f;
    mm[2] = 0.0f; mm[6] = 0.0f; mm[10] = 1.0f; mm[14] = 0.0f;
    mm[3] = 0.0f; mm[7] = 0.0f; mm[11] = 0.0f; mm[15] = 1.0f;

    modelMatrix = BufferUtils.newFloatBuffer(16);
    modelMatrix.put(mm);
    modelMatrix.rewind();

    Gdx.gl.glUniformMatrix4fv(modelMatrixLoc, 1, false, modelMatrix);

    //COLOR IS SET HERE
    Gdx.gl.glUniform4f(colorLoc, 0.7f, 0.2f, 0, 1);


    //VERTEX ARRAY IS FILLED HERE
    float[] array = {-50.0f, -50.0f,
                    -50.0f, 50.0f,
                    50.0f, -50.0f,
                    50.0f, 50.0f};

    vertexBuffer = BufferUtils.newFloatBuffer(8);
    vertexBuffer.put(array);
    vertexBuffer.rewind();

    position_x = 300;
    position_y = 300;

    screenWidth = Gdx.graphics.getWidth();
    screenHeight = Gdx.graphics.getHeight();

    size_rect = size_rect / 2;
}

private void update()
{
    if(Gdx.input.justTouched())
    {
        position_x = Gdx.input.getX();
        position_y = screenHeight - Gdx.input.getY();

        vertexBuffer.put(0, position_x - size_rect);
        vertexBuffer.put(1, position_y - size_rect);
        vertexBuffer.put(2, position_x - size_rect);
        vertexBuffer.put(3, position_y + size_rect);
        vertexBuffer.put(4, position_x + size_rect);
        vertexBuffer.put(5, position_y - size_rect);
        vertexBuffer.put(6, position_x + size_rect);
        vertexBuffer.put(7, position_y + size_rect);


    }

    Gdx.gl.glVertexAttribPointer(positionLoc, 2, GL20.GL_FLOAT, false, 0, vertexBuffer);
    Gdx.gl.glDrawArrays(GL20.GL_TRIANGLE_STRIP, 0, 4);

}

@Override
public void render () {

    Gdx.gl.glClearColor( 0.7f, 1f, 1f, 1f );
    Gdx.gl.glClear( GL20.GL_COLOR_BUFFER_BIT );

    update();
}
}

不幸的是，我不知道如何動態地“保存”矩形（或坐標）。

有人對我有個很好的建議，還是一個簡短的代碼示例，說明了如何做到這一點？

Answer 1

只需擁有一個用於存儲最新矩形頂點的起始索引的變量和另一個用於保存矩形數量的變量。

private int m_numRectangles;
private int m_nextRectIndex;

//initialize both above variables to 0

//...

if(Gdx.input.justTouched())
{
    m_nextRectIndex = m_numRectangles * 8;
    m_numRectangles++;

    //save a copy of the old rectangles
    vertexBuffer.rewind();
    Float[] oldRects = new Float[ vertexBuffer.remaining() ];
    vertexBuffer.get(oldRects);

    //allocate more memory for old + one more rectangle
    vertexBuffer = BufferUtils.newFloatBuffer( m_numRectangles * 8 );

    //copy back the old rectangles
    vertexBuffer.put( oldbuffer );
    vectexBuffer.rewind();

    position_x = Gdx.input.getX();
    position_y = screenHeight - Gdx.input.getY();

    vertexBuffer.put(m_nextRectIndex + 0, position_x - size_rect);
    vertexBuffer.put(m_nextRectIndex + 1, position_y - size_rect);
    vertexBuffer.put(m_nextRectIndex + 2, position_x - size_rect);
    vertexBuffer.put(m_nextRectIndex + 3, position_y + size_rect);
    vertexBuffer.put(m_nextRectIndex + 4, position_x + size_rect);
    vertexBuffer.put(m_nextRectIndex + 5, position_y - size_rect);
    vertexBuffer.put(m_nextRectIndex + 6, position_x + size_rect);
    vertexBuffer.put(m_nextRectIndex + 7, position_y + size_rect);

}
Gdx.gl.glVertexAttribPointer(positionLoc, 2, GL20.GL_FLOAT, false, 0, vertexBuffer);
for( int i=0; i<m_numRectangles * 4; i+=4 )
{
    Gdx.gl.glDrawArrays(GL20.GL_TRIANGLE_STRIP, i, 4);
}