java - Android OpenGL ES...为什么教程总是正确渲染，而我的版本却随机不正确？

Question

我正在遵循 insanitydesign.com 中找到的教程集，这是 NeHe OpenGL 教程的 Android 版本。我在理解为什么教程版本似乎始终正确渲染而我的修改版本随机渲染完全错误时遇到了很多问题。有时，当程序加载时，问题会立即显现出来，但有时我必须在它出现之前旋转屏幕。您可以下载包含屏幕截图的 zip 文件，其中我将屏幕旋转了 12 次 from filedropper 。正如您所看到的，三角形通常会渲染，但有时会显得完全扭曲和弄脏。 Here is a link to my entire Eclipse project如果你好奇的话。

我怀疑问题出在我的 Shape.draw() 方法中，但我无法确定。

我相信这是相关代码:

GLRenderer.java

    private Shape shape;

public GLRenderer(){
    Log.i(this.toString(),"ctor");
    shape = Shape.makeTriangle();
}

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
    speedPerSecond = SystemClock.uptimeMillis();
    Log.d(this.toString(), ".onSurfaceCreated");

    gl.glShadeModel(GL10.GL_SMOOTH);            



    gl.glClearColor(1.0f, 0.0f, 0.0f, 0.5f);


    gl.glClearDepthf(1.0f);                     //Depth Buffer Setup



    gl.glEnable(GL10.GL_DEPTH_TEST);            //Enables Depth Testing
    gl.glDepthFunc(GL10.GL_LEQUAL);             //The Type Of Depth Testing To Do

    //Really Nice Perspective Calculations
    gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); 

}

@Override
public void onDrawFrame(GL10 gl) {

    gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
    gl.glLoadIdentity();

    shape.setX(0.0f);
    shape.setY(0.0f);
    shape.setZ(-6.0f);
    shape.draw(gl);
}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
    if(height == 0){
        height = 1;
    }
    gl.glViewport(0, 0, width, height);
    gl.glMatrixMode(GL10.GL_PROJECTION);
    gl.glLoadIdentity();


    GLU.gluPerspective(gl, 45.0f, (float)width / (float)height, 0.1f, 50.0f);


    gl.glMatrixMode(GL10.GL_MODELVIEW);
    gl.glLoadIdentity();


}

形状.java 包 com.smashing.test;

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

import javax.microedition.khronos.opengles.GL10;

import android.util.Log;

public class Shape implements IGLShape {

    public float getX(){
        return x;
    }

    public float getY(){
        return y;
    }

    public float getZ(){
        return z;
    }

    public void setX(float pX){
        x = pX;
    }

    public void setY(float pY){
        y = pY;
    }

    public void setZ(float pZ){
        z = pZ;
    }



    public static Shape makeTriangle(){
        Shape s = new Shape();
                /*
                 *  Is this correct?  I want to create a right triangle on screen like this
                 *  |\
                 *  | \
                 *  |  \
                 *  |   \
                 *  |____\  though with a 90/45/45 degree spread rather than this poor representation.
                 */
        float v[] = {
            0.0f, 1.0f, 0.0f,
            0.0f, 0.0f, 0.0f,
            1.0f, 0.0f, 0.0f
        };
        s.setVertices(v);
        return s;
    }

    public static Shape makeShapeFromVertices(float pVerts[]){
        Shape s = new Shape();
        s.setVertices(pVerts);
        return s;   
    }


    private float x = 0.0f;
    private float y = 0.0f;
    private float z = 0.0f;
    private float[] mVertices;
    private FloatBuffer mVertexBuffer;






    public void setVertices(float pVerts[]){
        mVertices = pVerts;
        ByteBuffer bb = ByteBuffer.allocateDirect(mVertices.length * 4);
        bb.order(ByteOrder.nativeOrder());
        mVertexBuffer = bb.asFloatBuffer();
        mVertexBuffer.put(mVertices);
        mVertexBuffer.position(0);
    }

    public float[] getVertices(){
        return mVertices;
    }

    private Shape(){

    }


    @Override
    public void draw(GL10 gl) {


        /*
         * I believe the problem is here... but I don't understand how or why?
         */
        gl.glTranslatef(x, y, z);
        gl.glFrontFace(GL10.GL_CW);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer);
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, mVertices.length);
        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glTranslatef(-x, -y, -z);

    }



}

编辑:我知道该教程与我的版本略有不同。我正在尝试从中推断和实验......我只是对这些差异感到非常惊讶和震惊，并且想知道它们为什么存在，以及如何避免我在渲染中发现的这种令人不快的结果方案。

Answer 1

你应该更换

glDrawArrays(GL10.GL_TRIANGLE_STRIP, ...)

与

glDrawArrays(GL10.GL_TRIANGLES, ...)

我认为当您绘制一个简单的三角形而不是四边形时，这就是问题的原因。

问候