我有两个点,每个点都有自己的 X 和 Y 值,并且它们具有相同的 Z 值。
我想要一个函数在这两点之间绘制圆柱体。
最佳答案
要构建具有两个给定点的圆柱体,您需要 vector 分析。您正在构建两个垂直 vector ,将它们添加到每个点并按正弦/余弦乘以半径进行缩放。 它接受所有点(旧代码有一个错误,因为它错过了长度的 sqrt() )。 现在它可以正常工作并使用 gl 例程绘制圆柱体;我在JOGL中测试了它。 为了更快地绘制,将firstPerpVector/secondPerpVector/points变量移动到私有(private)最终数组字段并在开始时初始化它们。
Java代码:
public float[] getFirstPerpVector(float x, float y, float z) {
float[] result = {0.0f,0.0f,0.0f};
// That's easy.
if (x == 0.0f || y == 0.0f || z == 0.0f) {
if (x == 0.0f)
result[0] = 1.0f;
else if (y == 0.0f)
result[1] = 1.0f;
else
result[2] = 1.0f;
}
else {
// If xyz is all set, we set the z coordinate as first and second argument .
// As the scalar product must be zero, we add the negated sum of x and y as third argument
result[0] = z; //scalp = z*x
result[1] = z; //scalp = z*(x+y)
result[2] = -(x+y); //scalp = z*(x+y)-z*(x+y) = 0
// Normalize vector
float length = 0.0f;
for (float f : result)
length += f*f;
length = (float) Math.sqrt(length);
for (int i=0; i<3; i++)
result[i] /= length;
}
return result;
}
public void drawCylinder(GL gl, float x1, float y1, float z1, float x2, float y2, float z2) {
final int X = 0,
Y = 1,
Z = 2;
// Get components of difference vector
float x = x1-x2,
y = y1-y2,
z = z1-z2;
float[] firstPerp = getFirstPerpVector(x,y,z);
// Get the second perp vector by cross product
float[] secondPerp = new float[3];
secondPerp[X] = y*firstPerp[Z]-z*firstPerp[Y];
secondPerp[Y] = z*firstPerp[X]-x*firstPerp[Z];
secondPerp[Z] = x*firstPerp[Y]-y*firstPerp[X];
// Normalize vector
float length = 0.0f;
for (float f : secondPerp)
length += f*f;
length = (float) Math.sqrt(length);
for (int i=0; i<3; i++)
secondPerp[i] /= length;
// Having now our vectors, here we go:
// First points; you can have a cone if you change the radius R1
final int ANZ = 32; // number of vertices
final float FULL = (float) (2.0f*Math.PI),
R1 = 4.0f; // radius
float[][] points = new float[ANZ+1][3];
for (int i=0; i<ANZ; i++) {
float angle = FULL*(i/(float) ANZ);
points[i][X] = (float) (R1*(Math.cos(angle)*firstPerp[X]+Math.sin(angle)*secondPerp[X]));
points[i][Y] = (float) (R1*(Math.cos(angle)*firstPerp[Y]+Math.sin(angle)*secondPerp[Y]));
points[i][Z] = (float) (R1*(Math.cos(angle)*firstPerp[Z]+Math.sin(angle)*secondPerp[Z]));
}
// Set last to first
System.arraycopy(points[0],0,points[ANZ],0,3);
gl.glColor3f(1.0f,0.0f,0.0f);
gl.glBegin(GL.GL_TRIANGLE_FAN);
gl.glVertex3f(x1,y1,z1);
for (int i=0; i<=ANZ; i++) {
gl.glVertex3f(x1+points[i][X],
y1+points[i][Y],
z1+points[i][Z]);
}
gl.glEnd();
gl.glBegin(GL.GL_TRIANGLE_FAN);
gl.glVertex3f(x2,y2,z2);
for (int i=0; i<=ANZ; i++) {
gl.glVertex3f(x2+points[i][X],
y2+points[i][Y],
z2+points[i][Z]);
}
gl.glEnd();
gl.glBegin(GL.GL_QUAD_STRIP);
for (int i=0; i<=ANZ; i++) {
gl.glVertex3f(x1+points[i][X],
y1+points[i][Y],
z1+points[i][Z]);
gl.glVertex3f(x2+points[i][X],
y2+points[i][Y],
z2+points[i][Z]);
}
gl.glEnd();
}
关于c++ - 如何在OpenGL中绘制连接两点的圆柱体,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1878257/