创建简单的立方体模型一半是黑色

garyliyong

1. int main( int argc, char** argv )
   
2. {
   
3.     osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array(8);
   
4.     (*vertices)[0].set( 0.0f, 0.0f, 0.0f );
   
5.     (*vertices)[1].set( 1.0f, 0.0f, 0.0f );
   
6.     (*vertices)[2].set( 1.0f, 0.0f, 1.0f );
   
7.     (*vertices)[3].set( 0.0f, 0.0f, 1.0f );
   
8. 
   
9.     (*vertices)[4].set( 0.0f, 1.0f, 0.0f );
   
10.     (*vertices)[5].set( 1.0f, 1.0f, 0.0f );
    
11.     (*vertices)[6].set( 1.0f, 1.0f, 1.0f );
    
12.     (*vertices)[7].set( 0.0f, 1.0f, 1.0f );
    
13. 
    
14. 
    
15.     osg::ref_ptr<osg::DrawElementsUInt> index = new osg::DrawElementsUInt(
    
16.         osg::DrawElementsUInt::TRIANGLES);
    
17.     index->push_back(0);index->push_back(1);index->push_back(2);
    
18.     index->push_back(0);index->push_back(2);index->push_back(3);
    
19.    
    
20.     index->push_back(1);index->push_back(5);index->push_back(2);
    
21.     index->push_back(2);index->push_back(5);index->push_back(6);
    
22. 
    
23.     index->push_back(6);index->push_back(5);index->push_back(4);
    
24.     index->push_back(6);index->push_back(4);index->push_back(7);
    
25. 
    
26.     index->push_back(7);index->push_back(4);index->push_back(0);
    
27.     index->push_back(7);index->push_back(0);index->push_back(3);
    
28. 
    
29.     index->push_back(0);index->push_back(5);index->push_back(1);
    
30.     index->push_back(0);index->push_back(4);index->push_back(5);
    
31. 
    
32.     index->push_back(3);index->push_back(6);index->push_back(2);
    
33.     index->push_back(3);index->push_back(7);index->push_back(6);
    
34. 
    
35.     osg::ref_ptr<osg::Vec3Array> normals = new osg::Vec3Array;
    
36.     normals->push_back(osg::Vec3(0,-1,0));
    
37.     normals->push_back(osg::Vec3(0,-1,0));
    
38.     normals->push_back(osg::Vec3(0,-1,0));
    
39.     normals->push_back(osg::Vec3(0,-1,0));
    
40.     normals->push_back(osg::Vec3(0,-1,0));
    
41.     normals->push_back(osg::Vec3(0,-1,0));
    
42. 
    
43.     normals->push_back(osg::Vec3(1,0,0));
    
44.     normals->push_back(osg::Vec3(1,0,0));
    
45.     normals->push_back(osg::Vec3(1,0,0));
    
46.     normals->push_back(osg::Vec3(1,0,0));
    
47.     normals->push_back(osg::Vec3(1,0,0));
    
48.     normals->push_back(osg::Vec3(1,0,0));
    
49. 
    
50.     normals->push_back(osg::Vec3(0,1,0));
    
51.     normals->push_back(osg::Vec3(0,1,0));
    
52.     normals->push_back(osg::Vec3(0,1,0));
    
53.     normals->push_back(osg::Vec3(0,1,0));
    
54.     normals->push_back(osg::Vec3(0,1,0));
    
55.     normals->push_back(osg::Vec3(0,1,0));
    
56. 
    
57.     normals->push_back(osg::Vec3(-1,0,0));
    
58.     normals->push_back(osg::Vec3(-1,0,0));
    
59.     normals->push_back(osg::Vec3(-1,0,0));
    
60.     normals->push_back(osg::Vec3(-1,0,0));
    
61.     normals->push_back(osg::Vec3(-1,0,0));
    
62.     normals->push_back(osg::Vec3(-1,0,0));
    
63. 
    
64.     normals->push_back(osg::Vec3(0,0,-1));
    
65.     normals->push_back(osg::Vec3(0,0,-1));
    
66.     normals->push_back(osg::Vec3(0,0,-1));
    
67.     normals->push_back(osg::Vec3(0,0,-1));
    
68.     normals->push_back(osg::Vec3(0,0,-1));
    
69.     normals->push_back(osg::Vec3(0,0,-1));
    
70. 
    
71.     normals->push_back(osg::Vec3(0,0,1));
    
72.     normals->push_back(osg::Vec3(0,0,1));
    
73.     normals->push_back(osg::Vec3(0,0,1));
    
74.     normals->push_back(osg::Vec3(0,0,1));
    
75.     normals->push_back(osg::Vec3(0,0,1));
    
76.     normals->push_back(osg::Vec3(0,0,1));
    
77. 
    
78.     osg::ref_ptr<osg::Geometry> cuboid = new osg::Geometry;
    
79.     cuboid->setVertexArray(vertices);
    
80.     cuboid->addPrimitiveSet(index);
    
81.     cuboid->setNormalArray(normals);
    
82.     cuboid->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
    
83. 
    
84.     osg::ref_ptr<osg::Geode> geode = new osg::Geode;
    
85.     geode->addDrawable(cuboid);
    
86. 
    
87.     osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer;
    
88.     viewer->setSceneData(geode);
    
89.     viewer->addEventHandler(new osgViewer::WindowSizeHandler);
    
90.     return viewer->run();
    
91. }

复制代码

今天测试创建简单的立方体，发现一个问题，模型有一半是黑色，不知道为什么？看了代码好像没什么问题，望达人指导一下？

ramy612

这应该是灯光设置的问题吧……系统默认的光照没找到的地方当然是黑色的！

garyliyong

ramy612 发表于 2012-8-6 21:40
这应该是灯光设置的问题吧……系统默认的光照没找到的地方当然是黑色的！

如果是这样的话，那添加shape里的box就不会出现这种情况，如果加上SmoothingVisitor自动生成法线，也不会有这个问题，这很奇怪的

liuzhiyu123

顺时针  逆时针 反了

garyliyong

liuzhiyu123 发表于 2012-8-7 07:54
顺时针  逆时针 反了

我都是按照逆时针画的呀？还请指出具体哪行代码？谢谢

木子匕

这不是很正常嘛！正面是亮着的，背面是黑的！把灯光关闭就全亮了

garyliyong

木子匕 发表于 2012-8-7 09:21
这不是很正常嘛！正面是亮着的，背面是黑的！把灯光关闭就全亮了

我有12个三角面片，不知道你有没有测试一下？很多三角面片正面也是黑色的呀 关闭光照是可以，但是显示就不真实了

gis_wudi

看你画这个立方体可真够费劲的,黑色还是应该是发现向量设置的问题,好好检查一下你的每个顶点

木子匕

貌似逆时针画的三角形是正面，法线默认指向外部！，你很多三角形面片正面也是黑的！看看是不是法线错了吧！

garyliyong

木子匕 发表于 2012-8-7 12:27
貌似逆时针画的三角形是正面，法线默认指向外部！，你很多三角形面片正面也是黑的！看看是不是法线错了吧！

这是一个很简单的单位立方体，顶点和法向是不会错的。看一下也不会花多长时间的，就是顶点坐标，顶点索引和顶点法向。而且顶点顺序和法向我都看过的。

木子匕

试了下！感觉怪怪的啊！一个面的2个三角形有的黑又得亮！不明所以

garyliyong

这个问题就没人能解释下吗？

garyliyong

array大侠呢？能不能解释下原因呀？在opengl里用顶点数组显示是没问题的

liuzhiyu123

cuboid->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
跟你前面设置的法线数组有冲突

garyliyong

liuzhiyu123 发表于 2012-8-9 08:03
cuboid->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
跟你前面设置的法线数组有冲突

你能说得更清楚一点吗？你的意思是我有8个顶点，就只需要设8个法向吗？但是公共顶点的法向在不同的面上应该是不一样的呀
。那我的法向该如何设置绑定模式呢？

liuzhiyu123

BIND_PER_PRIMITIVE 就行 只需要对每个三角面进行一次法线设置

garyliyong

liuzhiyu123 发表于 2012-8-9 10:33
BIND_PER_PRIMITIVE 就行 只需要对每个三角面进行一次法线设置

我试过了还是不行，不知道你有没有试一下？

liuzhiyu123

osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array(8);
        (*vertices)[0].set( 0.0f, 0.0f, 0.0f );
        (*vertices)[1].set( 1.0f, 0.0f, 0.0f );
        (*vertices)[2].set( 1.0f, 0.0f, 1.0f );
        (*vertices)[3].set( 0.0f, 0.0f, 1.0f );

        (*vertices)[4].set( 0.0f, 1.0f, 0.0f );
        (*vertices)[5].set( 1.0f, 1.0f, 0.0f );
        (*vertices)[6].set( 1.0f, 1.0f, 1.0f );
        (*vertices)[7].set( 0.0f, 1.0f, 1.0f );


        osg::ref_ptr<osg:rawElementsUInt> index = new osg::DrawElementsUInt(
                osg::DrawElementsUInt::TRIANGLES);
        index->push_back(0);index->push_back(1);index->push_back(2);
        index->push_back(0);index->push_back(2);index->push_back(3);

        index->push_back(1);index->push_back(5);index->push_back(2);
        index->push_back(2);index->push_back(5);index->push_back(6);

        index->push_back(6);index->push_back(5);index->push_back(4);
        index->push_back(6);index->push_back(4);index->push_back(7);

        index->push_back(7);index->push_back(4);index->push_back(0);
        index->push_back(7);index->push_back(0);index->push_back(3);

        index->push_back(0);index->push_back(5);index->push_back(1);
        index->push_back(0);index->push_back(4);index->push_back(5);

        index->push_back(3);index->push_back(6);index->push_back(2);
        index->push_back(3);index->push_back(7);index->push_back(6);

        osg::ref_ptr<osg::Vec3Array> normals = new osg::Vec3Array;
        normals->push_back(osg::Vec3(0,-1,0));
        normals->push_back(osg::Vec3(0,-1,0));
        //normals->push_back(osg::Vec3(0,-1,0));
        //normals->push_back(osg::Vec3(0,-1,0));
        //normals->push_back(osg::Vec3(0,-1,0));
        //normals->push_back(osg::Vec3(0,-1,0));

        normals->push_back(osg::Vec3(1,0,0));
        normals->push_back(osg::Vec3(1,0,0));
        //normals->push_back(osg::Vec3(1,0,0));
        //normals->push_back(osg::Vec3(1,0,0));
        //normals->push_back(osg::Vec3(1,0,0));
        //normals->push_back(osg::Vec3(1,0,0));

        normals->push_back(osg::Vec3(0,1,0));
        normals->push_back(osg::Vec3(0,1,0));
        //normals->push_back(osg::Vec3(0,1,0));
        //normals->push_back(osg::Vec3(0,1,0));
        //normals->push_back(osg::Vec3(0,1,0));
        //normals->push_back(osg::Vec3(0,1,0));

        normals->push_back(osg::Vec3(-1,0,0));
        normals->push_back(osg::Vec3(-1,0,0));
        //normals->push_back(osg::Vec3(-1,0,0));
        //normals->push_back(osg::Vec3(-1,0,0));
        //normals->push_back(osg::Vec3(-1,0,0));
        //normals->push_back(osg::Vec3(-1,0,0));

        normals->push_back(osg::Vec3(0,0,-1));
        normals->push_back(osg::Vec3(0,0,-1));
        //normals->push_back(osg::Vec3(0,0,-1));
        //normals->push_back(osg::Vec3(0,0,-1));
        //normals->push_back(osg::Vec3(0,0,-1));
        //normals->push_back(osg::Vec3(0,0,-1));

        normals->push_back(osg::Vec3(0,0,1));
        normals->push_back(osg::Vec3(0,0,1));
        //normals->push_back(osg::Vec3(0,0,1));
        //normals->push_back(osg::Vec3(0,0,1));
        //normals->push_back(osg::Vec3(0,0,1));
        //normals->push_back(osg::Vec3(0,0,1));

        osg::ref_ptr<osg::Geometry> cuboid = new osg::Geometry;
        cuboid->setVertexArray(vertices);
        cuboid->addPrimitiveSet(index);
        cuboid->setNormalArray(normals);
        cuboid->setNormalBinding(osg::Geometry::BIND_PER_PRIMITIVE);

        osg::ref_ptr<osg::Geode> geode = new osg::Geode;
        geode->addDrawable(cuboid);

garyliyong

liuzhiyu123 发表于 2012-8-10 09:29
osg::ref_ptr vertices = new osg::Vec3Array(8);
        (*vertices)[0].set( 0.0f, 0.0f, 0.0f );
        (*vertice ...

我按照你的方法试过了，确实可以，但是在比较弯曲的曲面这样画的话，会不光滑，比如说球体，所以还是得给每个顶点付法向量才行，这样的话代码该怎么写才行？

liuzhiyu123

考虑点重复吧，如果点数据不重复估计不能实现

garyliyong

liuzhiyu123 发表于 2012-8-16 11:06
考虑点重复吧，如果点数据不重复估计不能实现

本来就是想用顶点数组减少顶点数的，真的没其它方法？

array

使用SmoothingVisitor可以通过设置法线来模拟平滑的效果，如果要求更高的话，也许您得考虑细分着色器了

hunter_wwq

我想问一下，这个立方体画出来之后，该怎么明确的给每个面着上指定的颜色？我3D太菜了

array

setColorArray