给定一组3D点和直径大小,我想绘制一个与
Windows管道屏幕保护程序
http://answers.yahoo.com/question/index?qid=20080919090035AAO55Qv相同的3D管道.
我正在使用C和OpenGL.任何人都可以帮我找到可以告诉我如何实现这一目标的资源吗？
经过一番调查后,似乎我们必须做额外的工作才能使转折点看起来光滑.如果可能的话,我正在寻找一些示例代码来说明如何实现它
谢谢
我会告诉我如何做这样的屏幕保护程序.我的管道适合3d网格,每个单元格都是一个立方体：
Y^
|_______
/ 2 /| 0 vs 3
/______/ | 1 vs 4
| |1| 2 vs 5
| 3 | /
|______|/ -->X
/
-Z/
每个单元中的管道配置由六位描述 – 每侧一位. 0表示单元格为空,63表示有6个段位于中心.如果将组合分解为类型,则会很少：
>短棍,x6
>长棍,x3(0-3,1-4,2-5)
>拱门,x12(2 – 1,1 – 3,2 – 3)
> T形交叉口,x12(1 – 3 – 4)
>角,x8(2 – 1 – 3,2 – 3 – 4)
>十字架,x3(3 – 1 – 2 – 4)
>四段式集群,x12(1 – 2 – 3 – 4)
>五段集群,x6
>六段星,x1.
我使用圆环四分之一用于拱门(自我合成),球形三角形补丁用于角落和圆柱体用于其他一切.星形,十字形和五段在我的模型中只是相交的圆柱体.
编辑：C#中的一些代码(我希望它在某种程度上有用).
现场的所有内容都由三种模型组合而成 – 拱形,圆柱形和球形三角形贴片,旋转和渲染多次.所有模型都在顶点数组中.很快我遇到了性能问题并实现了简单的基于距离的LOD来对抗它.所以,我生成的不是每种模型,而是一系列具有不同细分数的模型.
/// <summary>
/// Generates full row of arch models and lod map
/// to render them.
/// </summary>
/// <param name="radius">Pipe radius</param>
/// <returns>Model with lod</returns>
Model GenerateArches(double radius)
{
//Determine total number of vertices for full row
LodEntry[] lod = new LodEntry[slicesLod.Length];
int totalVertices = 0;
int totalIndices = 0;
for (int level = 0; level < slicesLod.Length; ++level)
{
int sl = slicesLod[level];
int st = archStacksLod[level];
if (st < 3) st = 3;
int vertices = (sl + 1)*(st + 1);
int indices = ((sl + 1)*2 + 4)*(st) - 4;
lod[level].start = totalIndices;
totalVertices += vertices;
totalIndices += indices;
lod[level].count = indices;
}
int[] indexArray = new int[totalIndices];
VertexAttributes[] va = new VertexAttributes[totalVertices];
int vCounter = 0; //index for vertices
int iCounter = 0; //indices counter
for (int level = 0; level < slicesLod.Length; ++level)
{
int iOffset = vCounter;
int slices = slicesLod[level];
int stacks = archStacksLod[level];
if (stacks < 3) stacks = 3;
for (int st = 0; st <= stacks; ++st)
{
double a = Math.PI*0.5*st/stacks;
float texCoordS = st/(float) stacks;
for (int sl = 0; sl <= slices; ++sl)
{
double b = Math.PI*2*sl/slices;
float texCoordT = sl/(float) slices;
va[vCounter].S = texCoordS;
va[vCounter].T = texCoordT;
//point on central arch
double x0 = 0.5*Math.Sin(a);
double y0 = 0.5*Math.Cos(a);
const double z0 = 0;
//point displacement
double rx = radius*Math.Sin(a)*Math.Sin(b);
double ry = radius*Math.Cos(a)*Math.Sin(b);
double rz = radius*Math.Cos(b);
//normal factor
double nf = 1.0/Math.Sqrt(rx*rx + ry*ry + rz*rz);
va[vCounter].NX = (float)(rx * nf);
va[vCounter].NY = (float)(ry * nf);
va[vCounter].NZ = (float)(rz * nf);
//position
va[vCounter].X = (float) (x0 + rx);
va[vCounter].Y = (float) (y0 + ry);
va[vCounter].Z = (float) (z0 + rz);
++vCounter;
}
}
for (int stack = 0; stack < stacks; ++stack)
{
for (int slice = 0; slice <= slices; ++slice)
{
indexArray[iCounter++] = iOffset + stack * slices + slice + stack;
indexArray[iCounter++] = iOffset + (stack + 1) * slices + slice + 1 + stack;
}
if (stack < stacks - 1)
{
indexArray[iCounter++] = iOffset + stack * slices + slices + stack;
indexArray[iCounter++] = iOffset + stack * slices + slices + stack;
indexArray[iCounter++] = iOffset + (stack + 1) * slices + slices + 2 * (stack + 1) - stack;
indexArray[iCounter++] = iOffset + (stack + 1) * slices + slices + 2 * (stack + 1) - stack;
}
}
}
return new Model(va,indexArray,lod);
}
/// <summary>
/// Generates indices for rendering of vertex array,/// representing a cylinder section.
/// Vertices assumed to be stored slice by slice:
/// 0 1 2 3 ................... cylStacks-1,/// cylStacks .................. 2*cylStacks-1,/// ....................................,/// (cylSlices-1)*cylStacks .. cylSlices*cylStacks-1.
/// </summary>
/// <param name="radius"></param>
private Model GenerateCylinders(double radius)
{
LodEntry[] lod = new LodEntry[slicesLod.Length];
int totalVertices = 0;
int totalIndices = 0;
for (int level = 0; level < slicesLod.Length; ++level)
{
int sl = slicesLod[level];
int st = cylStacksLod[level];
int vertices = (sl + 1)*(st + 1);
int indices = ((sl+1)*2 + 4)*st - 4;
lod[level].start = totalIndices;
totalVertices += vertices;
totalIndices += indices;
lod[level].count = indices;
}
int[] indexArray = new int[totalIndices];
VertexAttributes[] va = new VertexAttributes[totalVertices];
int vCounter = 0; //index for vertex attributes
int iCounter = 0; //indices counter
for (int level = 0; level < slicesLod.Length; ++level)
{
int iOffset = vCounter;
int slices = slicesLod[level];
int stacks = cylStacksLod[level];
for (int st = 0; st <= stacks; ++st)
{
double i = 0.5 - 0.5 * st / stacks;
float texCoordS = st / (float)stacks;
for (int sl = 0; sl <= slices; ++sl)
{
double b = Math.PI * 2 * sl / slices;
//tex coords
float texCoordT = sl / (float)slices;
va[vCounter].S = 0.5f * texCoordS;
va[vCounter].T = texCoordT;
//point on central axis
const double x0 = 0;
const double y0 = 0;
double z0 = i;
//point displacement
double rx = radius*Math.Cos(b);
double ry = radius*Math.Sin(b);
const double rz = 0;
//normal factor
double nf = 1.0/Math.Sqrt(ry*ry + rx*rx);
va[vCounter].NX = (float)(rx * nf);
va[vCounter].NY = (float)(ry * nf);
va[vCounter].NZ = 0.0f;
va[vCounter].X = (float)(x0 + rx);
va[vCounter].Y = (float)(y0 + ry);
va[vCounter].Z = (float)(z0 + rz);
++vCounter;
}
}
for (int stack = 0; stack < stacks; ++stack)
{
for (int slice = 0; slice <= slices; ++slice)
{
indexArray[iCounter++] = iOffset + stack*slices + slice + stack;
indexArray[iCounter++] = iOffset + (stack + 1)*slices + slice + 1 + stack;
}
if (stack < stacks - 1)
{
indexArray[iCounter++] = iOffset + stack * slices + slices + stack;
indexArray[iCounter++] = iOffset + stack * slices + slices + stack;
indexArray[iCounter++] = iOffset + (stack + 1) * slices + slices + 2 * (stack + 1) - stack;
indexArray[iCounter++] = iOffset + (stack + 1) * slices + slices + 2 * (stack + 1) - stack;
}
}
}
return new Model(va,lod);
}
static int R0(int _slices,int _level)
{
return _level * (_slices+2) - (int)(0.5 * _level * (_level + 1));
}
static int RL(int _slices,int _level)
{
return _slices - _level + 1;
}
private Model GenerateSphereSegment(double radius)
{
//Determine total number of vertices for full row
LodEntry[] lod = new LodEntry[slicesLod.Length];
int totalVertices = 0;
int totalIndices = 0;
for (int level = 0; level < slicesLod.Length; ++level)
{
int sl = slicesLod[level] >> 2;
int vertices = (((2 + sl) * (sl + 1)) >> 1);
int indices = sl * (sl + 3);
lod[level].start = totalIndices;
totalVertices += vertices;
totalIndices += indices;
lod[level].count = indices;
}
int[] indexArray = new int[totalIndices];
VertexAttributes[] va = new VertexAttributes[totalVertices];
int vCounter = 0; //index for vertices
int iCounter = 0; //indices counter
for (int level = 0; level < slicesLod.Length; ++level)
{
int sphSlices = slicesLod[level]>>2;
int iOffset = vCounter; //index offset for level
for (int sl = 0; sl <= sphSlices; ++sl)
{
double a = Math.PI*sl*0.5/sphSlices;
double Y = radius*Math.Sin(a);
double Ry = radius*Math.Cos(a);
for (int st = 0; st <= sphSlices - sl; ++st)
{
double X,Z,b;
if (sphSlices > sl)
{
b = Math.PI*0.5*st/(sphSlices - sl);
X = Ry*Math.Sin(b);
Z = Ry*Math.Cos(b);
}
else
{
X = 0;
Z = 0;
b = 0;
}
va[vCounter].S = (float)(0.5 / 3 * a);
va[vCounter].T = (float)(0.14 * b);
double coeff = 1/Math.Sqrt(X*X + Y*Y + Z*Z);
va[vCounter].NX = (float)(X * coeff);
va[vCounter].NY = (float)(Y * coeff);
va[vCounter].NZ = (float)(Z * coeff);
va[vCounter].X = (float)(va[vCounter].NX * radius);
va[vCounter].Y = (float)(va[vCounter].NY * radius);
va[vCounter].Z = (float)(va[vCounter].NZ * radius);
++vCounter;
}
}
for (int k = 0; k < sphSlices; ++k)
{
int lastS = RL(sphSlices,k);
for (int s = 0; s < lastS - 1; ++s)
{
int c0 = R0(sphSlices,k) + s;
int cn = R0(sphSlices,k) + s + RL(sphSlices,k);
indexArray[iCounter++] = cn + iOffset;
indexArray[iCounter++] = c0 + iOffset;
}
int tail = R0(sphSlices,k) + lastS - 1;
indexArray[iCounter++] = tail + iOffset;
indexArray[iCounter++] = tail + iOffset;
}
}
return new Model(va,lod);
}
