LWJGL VBO 三角形纹理坐标不起作用

Posted 2023-02-22

【中文标题】LWJGL VBO 三角形纹理坐标不起作用

【英文标题】：LWJGL VBO Triangle Texture Coordinates Not Working

【发布时间】：2014-01-30 19:49:12

【问题描述】：

由于使用三角形渲染比使用四边形渲染更快，我决定将我的 6 个四边形面分成 12 个三角形。我坚持的部分是我不知道如何将四边形纹理应用于三角形表面。下面的图片是我的尝试，但看起来很奇怪。谁能解释发生了什么，并告诉我如何解决这个问题？

截图：http://i.snag.gy/2ZenI.jpg

BlockFace 类：

public class BlockFace 
    private final int amountOfVertices = 3;
    private final int vertexSize = 3;
    private final int textureSize = 2;
    private final int amountOfFaces = 2;

    private int vbo; // vertices
    private int tbo; // texture coordinates

    public BlockFace(float[] vertices) 
        FloatBuffer vertexData = BufferUtils.createFloatBuffer(amountOfVertices * vertexSize * amountOfFaces);
        vertexData.put(vertices);
        vertexData.flip();

        FloatBuffer textureData = BufferUtils.createFloatBuffer(4 * textureSize * amountOfFaces);
        textureData.put(new float[] 
                0, 0,
                1, 0,
                1, 1,
                0, 1,

                0, 0,
                1, 0,
                1, 1,
                0, 1
        );
        textureData.flip();

        vbo = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, vertexData, GL_STATIC_DRAW);
        glBindBuffer(GL_ARRAY_BUFFER, 0);

        tbo = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, tbo);
        glBufferData(GL_ARRAY_BUFFER, textureData, GL_STATIC_DRAW);
        glBindBuffer(GL_ARRAY_BUFFER, 0);
    

    public void draw(Texture texture) 
        texture.bind();

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glVertexPointer(vertexSize, GL_FLOAT, 0, 0L);

        glBindBuffer(GL_ARRAY_BUFFER, tbo);
        glTexCoordPointer(textureSize, GL_FLOAT, 0, 0L);

        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);
        glDrawArrays(GL_TRIANGLES, 0, amountOfVertices * 2);
        glDisableClientState(GL_VERTEX_ARRAY);
        glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    

BlockRenderer 类：

public class BlockRenderer 
    private BlockFace topBlockFace;
    private BlockFace bottomBlockFace;
    private BlockFace frontBlockFace;
    private BlockFace backBlockFace;
    private BlockFace leftBlockFace;
    private BlockFace rightBlockFace;

    public BlockRenderer() 
        topBlockFace = new BlockFace(new float[] 
            0, 1, 0,
            1, 1, 0,
            0, 1, 1,

            1, 1, 1,
            1, 1, 0,
            0, 1, 1
        );
        bottomBlockFace = new BlockFace(new float[] 
            0, 0, 0,
            1, 0, 0,
            0, 0, 1,

            1, 0, 1,
            1, 0, 0,
            0, 0, 1
        );
        frontBlockFace = new BlockFace(new float[] 
            0, 0, 1,
            0, 1, 1,
            1, 1, 1,

            0, 0, 1,
            1, 0, 1,
            1, 1, 1
        );
        backBlockFace = new BlockFace(new float[] 
            0, 0, 0,
            0, 1, 0,
            1, 1, 0,

            0, 0, 0,
            1, 0, 0,
            1, 1, 0
        );
        leftBlockFace = new BlockFace(new float[] 
            0, 1, 0,
            0, 1, 1,
            0, 0, 1,

            0, 1, 0,
            0, 0, 0,
            0, 0, 1
        );
        rightBlockFace = new BlockFace(new float[] 
            1, 1, 0,
            1, 1, 1,
            1, 0, 1,

            1, 1, 0,
            1, 0, 0,
            1, 0, 1
        );
    

    public void renderBlock(Block block, float x, float y, float z) 
        glPushMatrix();
        glTranslatef(x, y, z);

        topBlockFace.draw(block.getTexture());
        bottomBlockFace.draw(block.getTexture());
        frontBlockFace.draw(block.getTexture());
        backBlockFace.draw(block.getTexture());
        leftBlockFace.draw(block.getTexture());
        rightBlockFace.draw(block.getTexture());

        glPopMatrix();
    

【参考方案1】：

如果将顶点划分为三角形，则必须将纹理坐标也划分为三角形。这意味着，每个面需要 6 个纹理坐标，就像每个面有 6 个顶点一样。

对于您的示例，您需要更改为：

FloatBuffer textureData = BufferUtils.createFloatBuffer(amountOfVertices * textureSize * amountOfFaces);
for(int i = 0; i < amountOfFaces; i++) 
    textureData.put(new float[] 
            0, 0,
            1, 0,
            0, 1,

            1, 1,
            1, 0,
            0, 1
    );

textureData.flip();

我还看到，每个四边形的一个三角形是顺时针定义的，而另一个是逆时针定义的。如果您使用剔除面，您将只能看到其中一个三角形。