LWJGL播放器運行狀況欄未正確定位

Question

我正在使用LWJGL和slick_util在Java中進行遊戲，最近我試圖實現一個健身欄，它將懸停在玩家頭頂上。問題是，它沒有正確定位。健康欄的左下角（從OpenGL開始繪製的地方）總是出現在玩家矩形的右上角，當玩家以x或y或兩者移動時，健康欄會以相同方向遠離玩家。我認爲這可能是glTranslatef的一個問題，或者是我錯過了一些愚蠢的東西。

渲染播放器的方法：

protected void render() { 
     Draw.rect(x, y, 32, 32, tex); //Player texture drawn 
     Draw.rect(x, y + 33, 32, 15, 1, 0, 0); //Health bar drawn. x is the same as player's, but y is +33 because I want it to hover on top 
    } 

抽獎類：

package rpgmain; 
import static org.lwjgl.opengl.GL11.*; 
import org.newdawn.slick.opengl.*; 
/** 
* 
* @author Samsung 
*/ 
public class Draw { 

    public static void rect(float x, float y, float width, float height, Texture tex) { 
     glEnable(GL_TEXTURE_2D); 
     glTranslatef(x, y, 0);   
     glColor4f(1f, 1f, 1f, 1f); 
     tex.bind(); 
     glBegin(GL_QUADS); //Specifies to the program where the drawing code begins. just to keep stuff neat. GL_QUADS specifies the type of shape you're going to be drawing. 
     { 
      //PNG format for images 
      glTexCoord2f(0,1); glVertex2f(0, 0); //Specify the vertices. 0, 0 is on BOTTOM LEFT CORNER OF SCREEN. 
      glTexCoord2f(0,0); glVertex2f(0, height); //2f specifies the number of args we're taking(2) and the type (float) 
      glTexCoord2f(1,0); glVertex2f(width, height); 
      glTexCoord2f(1,1); glVertex2f(width, 0); 
     } 
     glEnd(); 
     glDisable(GL_TEXTURE_2D); 
    } 

    public static void rect(float x, float y, float width, float height, float r, float g, float b) { 
     glDisable(GL_TEXTURE_2D); 
     glTranslatef(x, y, 0); 
     glColor3f(r, g, b); 

     glBegin(GL_QUADS); //Specifies to the program where the drawing code begins. just to keep stuff neat. GL_QUADS specifies the type of shape you're going to be drawing. 
     {     
      glVertex2f(0, 0); //Specify the vertices. 0, 0 is on BOTTOM LEFT CORNER OF SCREEN. 
      glVertex2f(0, height); //2f specifies the number of args we're taking(2) and the type (float) 
      glVertex2f(width, height); 
      glVertex2f(width, 0); 
     } 
     glEnd(); 
     glEnable(GL_TEXTURE_2D); 
    } 
} 

Answer 1

我覺得你的問題是與矩陣。當你調用glTranslatef時，你正在轉換OpenGL ModelView矩陣。但是，由於OpenGL是基於狀態的機器，因此爲了進一步繪製事件而保留了此轉換。第二個矩形將被翻譯兩次。你想要做的是使用OpenGL矩陣堆棧。我將改寫這裏的繪製方法：

public static void rect(float x, float y, float width, float height, Texture tex) { 
    glEnable(GL_TEXTURE_2D); 
    glPushMatrix(); 
    glTranslatef(x, y, 0);   
    glColor4f(1f, 1f, 1f, 1f); 
    tex.bind(); 
    glBegin(GL_QUADS); 
    { 
     glTexCoord2f(0,1); glVertex2f(0, 0); 
     glTexCoord2f(0,0); glVertex2f(0, height); 
     glTexCoord2f(1,0); glVertex2f(width, height); 
     glTexCoord2f(1,1); glVertex2f(width, 0); 
    } 
    glEnd(); 
    glPopMatrix(); 
    glDisable(GL_TEXTURE_2D); 
} 

線glPushMatrix（）將一個新的矩陣添加到堆棧的頂部。從這一點開始的所有轉換都將應用於新添加的矩陣。然後，當你調用glPopMatrix（）時，矩陣將被丟棄，並且堆棧返回到之前的狀態。