Hello, for a project I need to generate custom cylinder (i can not use ofCylinderPrimitive). The method that I’m using to draw a single cylinder (using OF_PRIMITIVE_TRIANGLE_STRIP) is explained here How to draw a cylinder starting from 2 ofNode.
In my mesh, i need to put together different cylinders, the problem is that sometimes there are surfaces between cylinder that should not be there. For example, this picture should compose a “Y”.
I’ve also tried to create the cylinders using OF_PRIMITIVE_TRIANGLES and specifying the indexes as follow, but I’ve the same problem.
//App.h
ofVboMesh mesh;
ofNode start;
ofNode end;
int resolution = 18;
float radius = 100.00;
// App.cpp
mesh.setMode(OF_PRIMITIVE_TRIANGLES);
for (int i = 0; i <= resolution; i++){
//calculate x and y component
float theta = 2.0f * 3.1415926f * float(i) / float(resolution);
float x = radius * cosf(theta);
float y = radius * sinf(theta);
ofVec3f circleTemp = ofVec3f(x, y, 0.0);
ofVec3f direction = (ofVec3f() + circleTemp).getNormalized();
// bottom
mesh.addVertex(circleTemp * start.getGlobalTransformMatrix());
mesh.addNormal(direction * start.getGlobalTransformMatrix());
//top
mesh.addVertex(circleTemp * end.getGlobalTransformMatrix());
mesh.addNormal(direction * end.getGlobalTransformMatrix());
}
int currentIndeces = mesh.getNumIndices();
for (int i = 0; i < resolution; i++){
int first = currentIndeces + i*2;
mesh.addIndex(first+1);
mesh.addIndex(first);
mesh.addIndex(first+2);
mesh.addIndex(first+2);
mesh.addIndex(first+3);
mesh.addIndex(first+1);
}
Does someone have an idea? Do i need to “close” the cylinders putting a cap on it?
I still didn’t have find a solution to this problem. What I’ve tired until now is to use the OF_PRIMITIVE_TRIANGLE_STRIP mode, as I’ve seen that is also used in the ofCylinferPrimitive. This is the code used to draw the picture in the previous post:
// SET THE POSITIONS
ofNode end;
ofNode start;
start.setPosition(-200, 0, 0);
end.setPosition(-200, 0, 200);
ofNode secondEnd;
secondEnd.setParent(end);
secondEnd.move(0, 200, 200);
ofNode thirdEnd;
thirdEnd.setParent(end);
thirdEnd.move(0, -200, 200);
mesh.setMode(OF_PRIMITIVE_TRIANGLE_STRIP);
// FIRST BRANCH
for (int i = 0; i <= resolution; i++){
//calculate x and y component
float theta = 2.0f * 3.1415926f * float(i) / float(resolution);
float x = radius * cosf(theta);
float y = radius * sinf(theta);
ofVec3f circleTemp = ofVec3f(x, y, 0.0);
ofVec3f direction = (ofVec3f() + circleTemp).getNormalized();
// bottom
mesh.addVertex(circleTemp * start.getGlobalTransformMatrix());
mesh.addNormal(direction * start.getGlobalTransformMatrix().getRotate());
//top
mesh.addVertex(circleTemp * end.getGlobalTransformMatrix());
mesh.addNormal(direction * end.getGlobalTransformMatrix().getRotate());
}
// SECOND BRANCH
for (int i = 0; i <= resolution; i++){
//calculate x and y component
float theta = 2.0f * 3.1415926f * float(i) / float(resolution);
float x = radius * cosf(theta);
float y = radius * sinf(theta);
ofVec3f circleTemp = ofVec3f(x, y, 0.0);
ofVec3f direction = (ofVec3f() + circleTemp).getNormalized();
// bottom
mesh.addVertex(circleTemp * end.getGlobalTransformMatrix());
mesh.addNormal(direction * end.getGlobalTransformMatrix().getRotate());
//top
mesh.addVertex(circleTemp * secondEnd.getGlobalTransformMatrix());
mesh.addNormal(direction * secondEnd.getGlobalTransformMatrix().getRotate());
}
// THIRD BRANCH
for (int i = 0; i <= resolution; i++){
//calculate x and y component
float theta = 2.0f * 3.1415926f * float(i) / float(resolution);
float x = radius * cosf(theta);
float y = radius * sinf(theta);
ofVec3f circleTemp = ofVec3f(x, y, 0.0);
ofVec3f direction = (ofVec3f() + circleTemp).getNormalized();
// bottom
mesh.addVertex(circleTemp * end.getGlobalTransformMatrix());
mesh.addNormal(direction * end.getGlobalTransformMatrix().getRotate());
//top
mesh.addVertex(circleTemp * thirdEnd.getGlobalTransformMatrix());
mesh.addNormal(direction * thirdEnd.getGlobalTransformMatrix().getRotate());
}
The code for each cylinder is always the same. I think the problem is happening at the end, where the last vertices of the mesh get connected. If I draw all the cylinder in a separate mesh, it is not a problem. But I’ve to build structure compose by a lot of cylinder, and it will be an overkill to have a separate mesh for each cylinder. Any suggestion is more than appreciated.
Solved. I’ve used OF_PRIMITIVE_TRIANGLE and I’ve specified the indexes that compose each face of the triangle. I don’t know if it is less performant than triangle strip(http://hacksoflife.blogspot.de/2010/01/to-strip-or-not-to-strip.html), but I don’t care, it is working fine in my case. I will post some code as reference here tomorrow.
