光线采摘混乱

Posted 2023-02-22

【中文标题】光线采摘混乱

【英文标题】：Ray picking mess

【发布时间】：2013-01-10 22:37:29

【问题描述】：

我正在使用光线拾取来查找角色的边界。这不是最佳的，但这是我能做的最好的，而且必须做的；我需要（接近）像素完美的碰撞，而且我有很多很多的对象。

但是，我没有让光线拾取正常工作。它发生了碰撞，但不是在正确的地方。我尝试调整射线的大小，但没有任何效果。

对不起，代码乱七八糟，我只是把它放在一起。

private void renderCollision(Vector3f dir)
    //
    // Render the models
    //

    glPushMatrix();
    glPushAttrib(GL_ALL_ATTRIB_BITS);

    float size = 10.0f;
    Picker.startPicking2D(10, 10, 20, 20, -1.0f, size);
    //Picker.startPicking2D(10, 10, 20, 20, 0.1f, 20.0f);

    glClear (GL_COLOR_BUFFER_BIT);
    glDisable(GL_BLEND);
    glDisable(GL_ALPHA);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glDepthMask(true);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    glClearDepth(100.0f);
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glDisable(GL_TEXTURE_2D);

    glLoadIdentity (); 


    //box.drawMoving(camera);
    player.move(dir);
    glTranslatef(-player.position.x, -player.position.y + size / 2.0f, -player.position.z);
    glRotatef(90.0f, 0.0f, 1.0f, 0.0f);

    box.drawAll();

    glDisable(GL_DEPTH_TEST);

    boolean hit = Picker.getHit();
    if (hit) 
        player.move(new Vector3f(-dir.x, -dir.y, -dir.z));
    

    Picker.stopPicking();

    glPopAttrib();
    glPopMatrix();


public class Picker 

    private static IntBuffer selBuffer;
    private static int hits;

    private static int xSelected;
    private static int ySelected;

    /**
     * Makes the game available for picking (when in 3D mode)
     *
     * @param xMouse The x coordinate of the mouse on the screen
     * @param yMouse The y coordinate of the mouse on the screen
     */
    public static void startPicking3D(int xMouse, int yMouse, int screenWidth, int screenHeight, float near, float far) 
        startPickingGeneric(xMouse, yMouse);

        GLU.gluPerspective(SCREEN_FOV, SCREEN_RAT,
                           near, far);

        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glLoadIdentity();
    

    /**
     * Makes the game available for picking (when in 2D mode)
     *
     * @param xMouse The x coordinate of the mouse on the screen
     * @param yMouse The y coordinate of the mouse on the screen
     */
    public static void startPicking2D(int xMouse, int yMouse, int screenWidth, int screenHeight, float near, float far) 
        startPickingGeneric(xMouse, yMouse);

        GL11.glOrtho(0, screenWidth, 0, screenHeight, near, far);

        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glLoadIdentity();
    

    /**
     * Makes the game available for picking (generic)
     *
     * @param xMouse The x coordinate of the mouse on the screen
     * @param yMouse The y coordinate of the mouse on the screen
     */
    private static void startPickingGeneric(int xMouse, int yMouse)
        // The selection buffer
        selBuffer = ByteBuffer.allocateDirect(1024).order(ByteOrder.nativeOrder()).
                    asIntBuffer();
        IntBuffer vpBuffer = ByteBuffer.allocateDirect(64).
                             order(ByteOrder.nativeOrder()).asIntBuffer();
        // Size of the viewport. [0] Is <x>, [1] Is <y>, [2] Is <width>, [3] Is <height>
        int[] viewport = new int[4];

        // Get the viewport info
        GL11.glGetInteger(GL11.GL_VIEWPORT, vpBuffer);
        vpBuffer.get(viewport);

        // Set the buffer that OpenGL uses for selection to our buffer
        GL11.glSelectBuffer(selBuffer);

        // Change to selection mode
        GL11.glRenderMode(GL11.GL_SELECT);

        // Initialize the name stack (used for identifying which object was selected)
        GL11.glInitNames();

        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glPushMatrix();
        GL11.glLoadIdentity();

        // Create 5x5 pixel picking region near cursor location
        GLU.gluPickMatrix((float) xMouse, (float) yMouse,
                          5.0f, 5.0f, IntBuffer.wrap(viewport));
    

    /**
     * Stops the picking mode
     */
    public static void stopPicking()
        GL11.glMatrixMode(GL11.GL_PROJECTION);
    GL11.glPopMatrix();
        GL11.glMatrixMode(GL11.GL_MODELVIEW);

        hits = 0;
        hits = GL11.glRenderMode(GL11.GL_RENDER);
    

    /**
     * Gets the tile the mouse points to
     *
     * @return TileCoords object with the coordinates of the selected tile
     */
    public static boolean getHit()

        int[] buffer = new int[256];
        xSelected = -1000;
        ySelected = -1000;

        selBuffer.get(buffer);

        if (hits > 0) 
              // If there were more than 0 hits
              xSelected = buffer[3]; // Make our selection the first object
              ySelected = buffer[4];
              int depth = buffer[1]; // Store how far away it is
              for (int i = 1; i < hits; i++) 
                    // Loop through all the detected hits
                    // If this object is closer to us than the one we have selected
                    if (buffer[i * 4 + 1] < (int) depth) 
                        xSelected = buffer[i * 4 + 3]; // Select the closest object
                        ySelected = buffer[i * 4 + 4];
                        depth = buffer[i * 4 + 1]; // Store how far away it is
                     
              
              return true;
        
        return false;
    

【问题讨论】：

“pickelperfect 碰撞”？

@gepfault：是的，像泡菜一样绿:')

不要使用固定功能管道！

@Felix K.：我刚读到这个，这显然是有争议的，但较新的显卡确实可以使用着色器更快。如果我非常需要性能提升，我会记住这一点。谢谢！

@RobotRock 还有其他一些原因，不仅是关于性能，而且你更灵活，这是主要原因，ffp 已被弃用。

【参考方案1】：

我应该绕 x 轴而不是 y 轴旋转然后平移。