Android openGL ES 法线

Question

所以昨天我写了 WaveFront .obj 3D 模型加载器，它现在工作正常(虽然不支持所有内容)所以我写了简单的测试来在屏幕上绘制任何 3D 模型，在我为场景添加照明之前一切正常.光出现了，但法线似乎仍处于默认状态。我非常不确定在为法线生成缓冲区(如 GL_NORMAL_ARRAY、GL_ARRAY_BUFFER 等)时我应该使用什么作为目标，因为我找不到任何关于它使用缓冲区对象的教程:

package com.Ruuhkis.opengl;

import static javax.microedition.khronos.opengles.GL10.GL_COLOR_BUFFER_BIT;
import static javax.microedition.khronos.opengles.GL10.GL_VERTEX_ARRAY;

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

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
import javax.microedition.khronos.opengles.GL11;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.opengl.GLSurfaceView.Renderer;
import android.opengl.GLU;
import android.opengl.GLUtils;
import android.util.Log;

import com.Ruuhkis.opengl.model.Indices;
import com.Ruuhkis.opengl.model.Loader;
import com.Ruuhkis.opengl.model.Model;
import com.Ruuhkis.opengl.model.Polygon;
import com.Ruuhkis.opengl.model.Vertex;

public class TextureRenderer implements Renderer {

    private FloatBuffer vertexBuffer, normalBuffer;
    private ShortBuffer indexBuffer;
    private int attribVBO, attribIBO, attribNBO;
    private Context context;
    private float rotation = 0;
    private float[] vertices = 
        {-0.8f, -0.8f, 0f,
        0.8f, -0.8f, 0f,
        0.8f, 0.8f, 0f,
        -0.8f, 0.8f, 0f};

    private float[] normals = 
        {0f};

    private short[] indices =
        {0, 3, 2,
        0, 2, 1};

    public TextureRenderer(Context context) {
        this.context = context;

        Model model = Loader.loadModel(context.getAssets(), "test.txt");

        vertices = new float[model.getVerticeList().size() * 3];

        int i = 0;

        for(Vertex v: model.getVerticeList()) {
            vertices[i++] = v.getX();
            vertices[i++] = v.getY();
            vertices[i++] = v.getZ();
            //Log.v("vertice", v.toString() + " sa");
        }

        i = 0;

        indices = new short[model.getPolygonList().size() * 3];
        normals = new float[model.getPolygonList().size() * 3];

        for(Polygon p: model.getPolygonList()) {
            for(Indices in: p.getIndiceList()) {
                normals[i] = vertices[in.getNormalIndex()];
                indices[i++] = (short) in.getVertexIndex();         
            }
        }

        ByteBuffer buffer = ByteBuffer.allocateDirect(vertices.length * 4);
        buffer.order(ByteOrder.nativeOrder());
        vertexBuffer = buffer.asFloatBuffer();
        vertexBuffer.put(vertices);
        vertexBuffer.flip();

        buffer = ByteBuffer.allocateDirect(normals.length * 4);
        buffer.order(ByteOrder.nativeOrder());
        normalBuffer = buffer.asFloatBuffer();
        normalBuffer.put(normals);
        normalBuffer.flip();

        buffer = ByteBuffer.allocateDirect(indices.length * 2);
        buffer.order(ByteOrder.nativeOrder());
        indexBuffer = buffer.asShortBuffer();
        indexBuffer.put(indices);
        indexBuffer.flip();


    }

    @Override
    public void onDrawFrame(GL10 gl) {

        gl.glColor4f(1f, 0f, 0f, 1f);
        gl.glClear(GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);

        gl.glLoadIdentity();
        gl.glPushMatrix();
        gl.glTranslatef(0f, 0f, -10f);
        rotation += 1f;
        gl.glRotatef(rotation, 1f, 1f, 0f);
        gl.glEnableClientState(GL_VERTEX_ARRAY);
        gl.glEnableClientState(GL11.GL_NORMAL_ARRAY);

        GL11 gl11 = (GL11) gl;

        gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, attribVBO);
        gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, attribIBO);
        gl11.glBindBuffer(GL11.GL_NORMAL_ARRAY, attribNBO);
        gl11.glVertexPointer(3, GL10.GL_FLOAT, 0, 0);
        gl11.glNormalPointer(3, GL10.GL_FLOAT, 0);
        gl11.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_SHORT, 0);

        gl.glDisableClientState(GL11.GL_NORMAL_ARRAY);
        gl.glDisableClientState(GL_VERTEX_ARRAY);
        gl.glPopMatrix();
        gl.glFlush();
    }

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        gl.glViewport(0, 0, width, height);
        gl.glMatrixMode(GL10.GL_PROJECTION);
        gl.glLoadIdentity();
        GLU.gluPerspective(gl, 45f, (float)width / (float)height, 1f, 100f);
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glEnable(GL10.GL_DEPTH_TEST);
        //gl.glEnable(GL10.GL_LIGHTING);
        gl.glEnable(GL10.GL_LIGHTING);
        gl.glEnable(GL10.GL_LIGHT1);
        gl.glEnable(GL10.GL_COLOR_MATERIAL);
        gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_AMBIENT, FloatBuffer.wrap(new float[]{0f, 0f, 0f, 1f}));
        gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_DIFFUSE, FloatBuffer.wrap(new float[]{1f, 1f, 1f, 1f}));
        gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_SPECULAR, FloatBuffer.wrap(new float[]{1f, 1f, 1f, 1f}));

        gl.glMaterialfv(GL10.GL_FRONT, GL10.GL_SPECULAR, FloatBuffer.wrap(new float[]{1f, 1f, 1f, 1f}));
        gl.glMaterialf(GL11.GL_FRONT, GL11.GL_SHININESS,128f);
        gl.glShadeModel(GL10.GL_SMOOTH);
    }

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        gl.glClearColor(0.8f, 0.8f, 0.8f, 1f);
        GL11 gl11 = (GL11) gl;
        int[] buffer = new int[1];
        gl11.glGenBuffers(1, buffer, 0);
        attribVBO = buffer[0];
        gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, attribVBO);
        gl11.glBufferData(GL11.GL_ARRAY_BUFFER, vertices.length * 4, vertexBuffer, GL11.GL_STATIC_DRAW);
        gl11.glBindBuffer(GL11.GL_ARRAY_BUFFER, -1);

        gl11.glGenBuffers(1, buffer, 0);
        attribIBO = buffer[0];
        gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, attribIBO);
        gl11.glBufferData(GL11.GL_ELEMENT_ARRAY_BUFFER, indices.length * 2, indexBuffer, GL11.GL_STATIC_DRAW);
        gl11.glBindBuffer(GL11.GL_ELEMENT_ARRAY_BUFFER, -1);

        gl11.glGenBuffers(1, buffer, 0);
        attribNBO = buffer[0];
        gl11.glBindBuffer(GL11.GL_NORMAL_ARRAY, attribNBO);
        gl11.glBufferData(GL11.GL_NORMAL_ARRAY, normals.length * 4, normalBuffer, GL11.GL_STATIC_DRAW);
        gl11.glBindBuffer(GL11.GL_NORMAL_ARRAY, -1);
    }
}

因此，默认法线为 0、0、-1 或 0、0、1，并且默认相机正注视着 -5，随着模型旋转，光线就像没有法线时一样消失，我在计算机上有类似的东西，但我没有使用 VBO 等。所以我无法比较代码，我很确定上传普通缓冲区或绑定(bind)它有问题! :( 帮帮我!:(

Answer 1

进一步解释我对你的问题的评论:

你需要确保你的法线是“规范化的”；这意味着它们的量级(长度)必须为 1。一些 .obj 导出器会为您执行此操作；但自己做这件事是件好事。

引自:http://www.fundza.com/vectors/normalize/index.html

给定一个向量“a”(或正常的“a”):a[3 1 2](所以:ax = 3, ay = 1, az = 2)

向量的大小(长度)是:|a| = sqrt((ax * ax) + (ay * ay) + (az * az))

length = sqrt((ax * ax) + (ay * ay) + (az * az)) 
length = sqrt(9 + 1 + 4) = 3.742

为了归一化向量“a”，我们除以长度:

x = ax/|a|;
y = ay/|a|;
z = az/|a|;

x = 3.0 / 3.742 = 0.802
y = 1.0 / 3.742 = 0.267
z = 2.0 / 3.742 = 0.534

您需要在创建缓冲区之前将此应用到法线以获得正确的光照。