Question

所以我试图实现＆＃34; Polygon Art / Low Poly＆＃34;使用LibGDX的风格。我首先构建一个由三角形组成的模型。

然后使用顶点着色器，我根据高度计算每个顶点的颜色。

问题是，当我希望它像平面阴影一样时，地形是Gouraud阴影：

我知道，对于更高版本的OpenGL，有一个＆＃34;平坦的＆＃34; glsl中的关键字将禁用顶点之间的颜色插值。从我在网上和这篇文章中读到的内容：http://i.stack.imgur.com/DrNx9.jpg，我认为我需要让地形中的每个三角形彼此分开？我还需要计算每个三角形的法线？我无法理解其他StackOverflow中的代码，但这是我试图做的：

原始

public Model getWorld(){
    returnWorld = new Model();
    modelBuilder = new ModelBuilder();
    modelBuilder.begin();
    worldMeshBuilder = modelBuilder.part("worldPart", GL20.GL_TRIANGLES, Usage.Position | Usage.Normal, new Material());
    pieceMeshBuilder = new MeshBuilder();
    meshPiece = new Mesh(false, 3, 3, 
            new VertexAttribute(Usage.Position, 3, "a_position"), 
            new VertexAttribute(Usage.Normal, 3, "a_normal"), 
            new VertexAttribute(Usage.ColorPacked, 4, "a_color"));
    Vector3 vectorCopy = new Vector3();
    for(int i = 0; i < world.length - 1; i++){
        for(int j = 0; j < world[0].length - 1; j++){
            if((i + j) % 2 == 0){
                pieceMeshBuilder.begin(Usage.Position | Usage.Normal, renderType);
                pieceMeshBuilder.triangle(
                    vectorCopy = verticies[i][j],
                    vectorCopy = verticies[i][j + 1],
                    vectorCopy = verticies[i + 1][j + 1]
                );
                worldMeshBuilder.addMesh(pieceMeshBuilder.end());
                pieceMeshBuilder.begin(Usage.Position | Usage.Normal, renderType);
                pieceMeshBuilder.triangle(
                        vectorCopy = verticies[i + 1][j + 1],
                        vectorCopy = verticies[i + 1][j],
                        vectorCopy = verticies[i][j]
                );
                worldMeshBuilder.addMesh(pieceMeshBuilder.end());
            } else {
                pieceMeshBuilder.begin(Usage.Position | Usage.Normal, renderType);
                pieceMeshBuilder.triangle(
                    vectorCopy = verticies[i][j],
                    vectorCopy = verticies[i][j + 1],
                    vectorCopy = verticies[i + 1][j]
                );
                worldMeshBuilder.addMesh(pieceMeshBuilder.end());
                pieceMeshBuilder.begin(Usage.Position | Usage.Normal, renderType);
                pieceMeshBuilder.triangle(
                        vectorCopy = verticies[i + 1][j + 1],
                        vectorCopy = verticies[i + 1][j],
                        vectorCopy = verticies[i][j + 1]
                );
                worldMeshBuilder.addMesh(pieceMeshBuilder.end());
            }
        }
    }
    returnWorld = modelBuilder.end();
    return returnWorld;
}

现在：

public Model getWorld(){
    returnWorld = new Model();
    modelBuilder = new ModelBuilder();
    modelBuilder.begin();
    worldMeshBuilder = modelBuilder.part("worldPart", GL20.GL_LINES, Usage.Position | Usage.Normal, new Material());

    for(int i = 0; i < world.length - 1; i++){
        for(int j = 0; j < world[0].length - 1; j++){

            Vector3 normal1 = calcNormal(verticies[i][j], verticies[i + 1][j], verticies[i + 1][j + 1]);
            Vector3 normal2 = calcNormal(verticies[i][j], verticies[i + 1][j + 1], verticies[i][j + 1]);

            if((i + j) % 2 == 0){
                meshPiece = new Mesh(false, 18, 3, 
                        new VertexAttribute(Usage.Position, 3, "a_position"), 
                        new VertexAttribute(Usage.Normal, 3, "a_normal")//, 
                        //new VertexAttribute(Usage.ColorPacked, 4, "a_color")
                        );
                worldMeshBuilder.addMesh(meshPiece.setVertices(new float[] {
                        verticies[i][j].x, verticies[i][j].y, verticies[i][j].z, normal1.x, normal1.y, normal1.z,
                        verticies[i + 1][j].x, verticies[i + 1][j].y, verticies[i + 1][j].z, normal1.x, normal1.y, normal1.z, 
                        verticies[i + 1][j + 1].x, verticies[i + 1][j + 1].y, verticies[i + 1][j + 1].z, normal1.x, normal1.y, normal1.z,
                    }));
                meshPiece = new Mesh(false, 18, 3, 
                        new VertexAttribute(Usage.Position, 3, "a_position"), 
                        new VertexAttribute(Usage.Normal, 3, "a_normal")//, 
                        //new VertexAttribute(Usage.ColorPacked, 4, "a_color")
                        );
                worldMeshBuilder.addMesh(meshPiece.setVertices(new float[] {
                        verticies[i][j].x, verticies[i][j].y, verticies[i][j].z, normal2.x, normal2.y, normal2.z,
                        verticies[i + 1][j + 1].x, verticies[i + 1][j + 1].y, verticies[i + 1][j + 1].z, normal2.x, normal2.y, normal2.z, 
                        verticies[i][j + 1].x, verticies[i][j + 1].y, verticies[i][j + 1].z, normal2.x, normal2.y, normal2.z,
                    }));
            } else {
                meshPiece = new Mesh(false, 18, 3, 
                        new VertexAttribute(Usage.Position, 3, "a_position"), 
                        new VertexAttribute(Usage.Normal, 3, "a_normal")//, 
                        //new VertexAttribute(Usage.ColorPacked, 4, "a_color")
                        );
                worldMeshBuilder.addMesh(meshPiece.setVertices(new float[] {
                        verticies[i][j].x, verticies[i][j].y, verticies[i][j].z, normal1.x, normal1.y, normal1.z,
                        verticies[i + 1][j].x, verticies[i + 1][j].y, verticies[i + 1][j].z, normal1.x, normal1.y, normal1.z, 
                        verticies[i][j + 1].x, verticies[i][j + 1].y, verticies[i][j + 1].z, normal1.x, normal1.y, normal1.z,
                    }));
                meshPiece = new Mesh(false, 18, 3, 
                        new VertexAttribute(Usage.Position, 3, "a_position"), 
                        new VertexAttribute(Usage.Normal, 3, "a_normal")//, 
                        //new VertexAttribute(Usage.ColorPacked, 4, "a_color")
                        );
                worldMeshBuilder.addMesh(meshPiece.setVertices(new float[] {
                        verticies[i + 1][j].x, verticies[i + 1][j].y, verticies[i + 1][j].z, normal2.x, normal2.y, normal2.z,
                        verticies[i + 1][j + 1].x, verticies[i + 1][j + 1].y, verticies[i + 1][j + 1].z, normal2.x, normal2.y, normal2.z, 
                        verticies[i][j + 1].x, verticies[i][j + 1].y, verticies[i][j + 1].z, normal2.x, normal2.y, normal2.z,
                    }));
            }
        }
    }
    returnWorld = modelBuilder.end();
    return returnWorld;
}

问题是新代码没有渲染任何内容......我已经查看了ModelBuilder，MeshBuilder，Mesh和VertexAttribute / s的API，但我无法弄清楚它为什么不是＆＃39;工作。任何帮助都会很棒，因为这是非常令人沮丧的一天。非常感谢！

Answer 1

平坦和平滑的阴影通常由顶点法线以及如何在面部内插颜色来确定。

通常在平滑模型中，每个顶点的法线对于同一位置的每个面点进行平均。每个共享顶点位置的法线对于每个面都是相同的。这使得照明平滑，因为边缘没有突然的变化。

在平面着色模型中，顶点法线与相邻面不匹配，而是每个顶点法线与面法线相同。这会在边缘处产生正常值的突然变化。

这通常可以在您使用的任何3D建模包中进行修改，或者在程序生成地形时稍微修改您的正常生成代码。

下图显示平坦和平滑法线之间的差异。较深的蓝线代表平均平滑法线，较浅（青色）线代表严酷的法线正常。

您应该能够在一次绘制调用中将所有三角形绘制在一起。您不需要拆分网格。

LibGDX：如何使用OpenGL 2.0实现平面阴影外观？

1 个答案: