我有一个问题,我似乎无法找到一个可行的算法,我已经尝试了好几天,但距离如此之近。
我想绘制一个由 3 个点(p0、p1、p2)定义的三角形。这个三角形可以是任何形状、大小和方向。三角形也必须在里面填充。
以下是我尝试过的一些事情以及它们失败的原因:
1
- 沿着三角形从一边到另一边画线
- 失败,因为三角形会有孔,并且由于在有角度的表面上随着位置变化而画线的笨拙而不是平坦的
2
- 迭代一个区域并测试该点是否落在与三角形平行的平面以及投影到覆盖三角形区域的 XY、ZY 和 XZ 平面上的其他 3 个平面
- 失败是因为对于某些三角形(具有非常接近的边)会有不可预测的结果,例如漂浮在周围的体素没有连接到任何东西
3
- 沿着三角形的边迭代一个区域(线算法)并测试一个点是否越过平行平面
- 失败是因为从 p0 到 p1 画一条线与从 p1 到 p0 画一条线不同,任何重新排列的尝试都没有帮助,或者会导致更多问题。不对称是这个问题。
这都是为了制作多边形和平面。3 给了我最大的成功并制作了准确的三角形,但是当我尝试将它们连接在一起时,一切都崩溃了,我遇到了无法连接、不对称等问题。我相信 3 可以进行一些调整,但我只是磨损了从试图使这项工作这么长时间并需要帮助。
我的算法中有很多不相关的小细节,所以我把它们排除在外。对于数字 3,这可能是我的实现而不是算法本身的问题。如果您想要代码,我会尝试将其清理到足以理解的程度,不过这需要我几分钟。但我正在寻找已知有效的算法。我似乎在任何地方都找不到任何体素形状制作算法,我一直在从头开始做所有事情。
编辑:
这是第三次尝试。这是一个烂摊子,但我试图清理它。
// Point3i is a class I made, however the Vector3fs you'll see are from lwjgl
public void drawTriangle (Point3i r0, Point3i r1, Point3i r2)
{
// Util is a class I made with some useful stuff inside
// Starting values for iteration
int sx = (int) Util.min(r0.x, r1.x, r2.x);
int sy = (int) Util.min(r0.y, r1.y, r2.y);
int sz = (int) Util.min(r0.z, r1.z, r2.z);
// Ending values for iteration
int ex = (int) Util.max(r0.x, r1.x, r2.x);
int ey = (int) Util.max(r0.y, r1.y, r2.y);
int ez = (int) Util.max(r0.z, r1.z, r2.z);
// Side lengths
float l0 = Util.distance(r0.x, r1.x, r0.y, r1.y, r0.z, r1.z);
float l1 = Util.distance(r2.x, r1.x, r2.y, r1.y, r2.z, r1.z);
float l2 = Util.distance(r0.x, r2.x, r0.y, r2.y, r0.z, r2.z);
// Calculate the normal vector
Vector3f nn = new Vector3f(r1.x - r0.x, r1.y - r0.y, r1.z - r0.z);
Vector3f n = new Vector3f(r2.x - r0.x, r2.y - r0.y, r2.z - r0.z);
Vector3f.cross(nn, n, n);
// Determines which direction we increment for
int iz = n.z >= 0 ? 1 : -1;
int iy = n.y >= 0 ? 1 : -1;
int ix = n.x >= 0 ? 1 : -1;
// Reorganize for the direction of iteration
if (iz < 0) {
int tmp = sz;
sz = ez;
ez = tmp;
}
if (iy < 0) {
int tmp = sy;
sy = ey;
ey = tmp;
}
if (ix < 0) {
int tmp = sx;
sx = ex;
ex = tmp;
}
// We're we want to iterate over the end vars so we change the value
// by their incrementors/decrementors
ex += ix;
ey += iy;
ez += iz;
// Maximum length
float lmax = Util.max(l0, l1, l2);
// This is a class I made which manually iterates over a line, I already
// know that this class is working
GeneratorLine3d g0, g1, g2;
// This is a vector for the longest side
Vector3f v = new Vector3f();
// make the generators
if (lmax == l0) {
v.x = r1.x - r0.x;
v.y = r1.y - r0.y;
v.z = r1.z - r0.z;
g0 = new GeneratorLine3d(r0, r1);
g1 = new GeneratorLine3d(r0, r2);
g2 = new GeneratorLine3d(r2, r1);
}
else if (lmax == l1) {
v.x = r1.x - r2.x;
v.y = r1.y - r2.y;
v.z = r1.z - r2.z;
g0 = new GeneratorLine3d(r2, r1);
g1 = new GeneratorLine3d(r2, r0);
g2 = new GeneratorLine3d(r0, r1);
}
else {
v.x = r2.x - r0.x;
v.y = r2.y - r0.y;
v.z = r2.z - r0.z;
g0 = new GeneratorLine3d(r0, r2);
g1 = new GeneratorLine3d(r0, r1);
g2 = new GeneratorLine3d(r1, r2);
}
// Absolute values for the normal
float anx = Math.abs(n.x);
float any = Math.abs(n.y);
float anz = Math.abs(n.z);
int i, o;
int si, so;
int ii, io;
int ei, eo;
boolean maxx, maxy, maxz,
midy, midz, midx,
minx, miny, minz;
maxx = maxy = maxz =
midy = midz = midx =
minx = miny = minz = false;
// Absolute values for the longest side vector
float rnx = Math.abs(v.x);
float rny = Math.abs(v.y);
float rnz = Math.abs(v.z);
int rmid = Util.max(rnx, rny, rnz);
if (rmid == rnz) midz = true;
else if (rmid == rny) midy = true;
midx = !midz && !midy;
// Determine the inner and outer loop directions
if (midz) {
if (any > anx)
{
maxy = true;
si = sy;
ii = iy;
ei = ey;
}
else {
maxx = true;
si = sx;
ii = ix;
ei = ex;
}
}
else {
if (anz > anx) {
maxz = true;
si = sz;
ii = iz;
ei = ez;
}
else {
maxx = true;
si = sx;
ii = ix;
ei = ex;
}
}
if (!midz && !maxz) {
minz = true;
so = sz;
eo = ez;
}
else if (!midy && !maxy) {
miny = true;
so = sy;
eo = ey;
}
else {
minx = true;
so = sx;
eo = ex;
}
// GeneratorLine3d is iterable
Point3i p1;
for (Point3i p0 : g0) {
// Make sure the two 'mid' coordinate correspond for the area inside the triangle
if (midz)
do p1 = g1.hasNext() ? g1.next() : g2.next();
while (p1.z != p0.z);
else if (midy)
do p1 = g1.hasNext() ? g1.next() : g2.next();
while (p1.y != p0.y);
else
do p1 = g1.hasNext() ? g1.next() : g2.next();
while (p1.x != p0.x);
eo = (minx ? p0.x : miny ? p0.y : p0.z);
so = (minx ? p1.x : miny ? p1.y : p1.z);
io = eo - so >= 0 ? 1 : -1;
for (o = so; o != eo; o += io) {
for (i = si; i != ei; i += ii) {
int x = maxx ? i : midx ? p0.x : o;
int y = maxy ? i : midy ? p0.y : o;
int z = maxz ? i : midz ? p0.z : o;
// isPassing tests to see if a point goes past a plane
// I know it's working, so no code
// voxels is a member that is an arraylist of Point3i
if (isPassing(x, y, z, r0, n.x, n.y, n.z)) {
voxels.add(new Point3i(x, y, z));
break;
}
}
}
}
}