glVertex3f and glVertex2fx displaying different results
0
I suspect it has to do with my conversion code:
vector3::operator float*() const
{
// x, y, z are member floats
float arr[3];
arr[0] = x;
arr[1] = y;
arr[2] = z;
return arr;
}
Then in another class I do:
glBegin(GL_POLYGON);
glVertex3fv(origin); // wrong result
//glVertex3f(origin.x, origin.y, origin.z); // good
//glVertex3f(0.0, 0.0, 0.0); // also good
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
The problem is that the rectangle is stretched very far. I suspect it is because of the way I am passing the argument.
c++ arrays opengl casting
asked Nov 21 at 5:44
jinenofu
1
|
show 2 more comments
0
I suspect it has to do with my conversion code:
vector3::operator float*() const
{
// x, y, z are member floats
float arr[3];
arr[0] = x;
arr[1] = y;
arr[2] = z;
return arr;
}
Then in another class I do:
glBegin(GL_POLYGON);
glVertex3fv(origin); // wrong result
//glVertex3f(origin.x, origin.y, origin.z); // good
//glVertex3f(0.0, 0.0, 0.0); // also good
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
The problem is that the rectangle is stretched very far. I suspect it is because of the way I am passing the argument.
c++ arrays opengl casting
asked Nov 21 at 5:44
jinenofu
1
Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
4
float arr[3];is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.
– Rabbid76
Nov 21 at 5:55
What isorigin?glVertex3fvexpects a pointer to 3 contiguousGLfloats. Are you sure thatoriginhas a type which grants this? What type does it actually have?
– Scheff
Nov 21 at 7:18
I assume, you want to callglVertexfor your DIY typevector3? How about an "overload"? E.g.void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); }Then, you could do e.g.vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)
– Scheff
Nov 21 at 7:21
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources ofvector3it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.
– Bartek Banachewicz
Nov 21 at 8:49
|
show 2 more comments
0
0
0
I suspect it has to do with my conversion code:
vector3::operator float*() const
{
// x, y, z are member floats
float arr[3];
arr[0] = x;
arr[1] = y;
arr[2] = z;
return arr;
}
Then in another class I do:
glBegin(GL_POLYGON);
glVertex3fv(origin); // wrong result
//glVertex3f(origin.x, origin.y, origin.z); // good
//glVertex3f(0.0, 0.0, 0.0); // also good
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
The problem is that the rectangle is stretched very far. I suspect it is because of the way I am passing the argument.
c++ arrays opengl casting
asked Nov 21 at 5:44
jinenofu
1
I suspect it has to do with my conversion code:
vector3::operator float*() const
{
// x, y, z are member floats
float arr[3];
arr[0] = x;
arr[1] = y;
arr[2] = z;
return arr;
}
Then in another class I do:
glBegin(GL_POLYGON);
glVertex3fv(origin); // wrong result
//glVertex3f(origin.x, origin.y, origin.z); // good
//glVertex3f(0.0, 0.0, 0.0); // also good
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
The problem is that the rectangle is stretched very far. I suspect it is because of the way I am passing the argument.
c++ arrays opengl casting
c++ arrays opengl casting
asked Nov 21 at 5:44
jinenofu
1
asked Nov 21 at 5:44
jinenofu
1
asked Nov 21 at 5:44
jinenofu
1
asked Nov 21 at 5:44
jinenofu
1
asked Nov 21 at 5:44
jinenofu
1
1
Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
4
float arr[3];is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.
– Rabbid76
Nov 21 at 5:55
What isorigin?glVertex3fvexpects a pointer to 3 contiguousGLfloats. Are you sure thatoriginhas a type which grants this? What type does it actually have?
– Scheff
Nov 21 at 7:18
I assume, you want to callglVertexfor your DIY typevector3? How about an "overload"? E.g.void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); }Then, you could do e.g.vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)
– Scheff
Nov 21 at 7:21
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources ofvector3it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.
– Bartek Banachewicz
Nov 21 at 8:49
|
show 2 more comments
Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
4
float arr[3];is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.
– Rabbid76
Nov 21 at 5:55
What isorigin?glVertex3fvexpects a pointer to 3 contiguousGLfloats. Are you sure thatoriginhas a type which grants this? What type does it actually have?
– Scheff
Nov 21 at 7:18
I assume, you want to callglVertexfor your DIY typevector3? How about an "overload"? E.g.void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); }Then, you could do e.g.vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)
– Scheff
Nov 21 at 7:21
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources ofvector3it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.
– Bartek Banachewicz
Nov 21 at 8:49
Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
4
4
float arr[3]; is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.– Rabbid76
Nov 21 at 5:55
float arr[3]; is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.– Rabbid76
Nov 21 at 5:55
What is
origin? glVertex3fv expects a pointer to 3 contiguous GLfloats. Are you sure that origin has a type which grants this? What type does it actually have?– Scheff
Nov 21 at 7:18
What is
origin? glVertex3fv expects a pointer to 3 contiguous GLfloats. Are you sure that origin has a type which grants this? What type does it actually have?– Scheff
Nov 21 at 7:18
I assume, you want to call
glVertex for your DIY type vector3? How about an "overload"? E.g. void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); } Then, you could do e.g. vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)– Scheff
Nov 21 at 7:21
I assume, you want to call
glVertex for your DIY type vector3? How about an "overload"? E.g. void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); } Then, you could do e.g. vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)– Scheff
Nov 21 at 7:21
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources of
vector3 it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.– Bartek Banachewicz
Nov 21 at 8:49
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources of
vector3 it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.– Bartek Banachewicz
Nov 21 at 8:49
|
show 2 more comments
1 Answer
1
active
oldest
votes
2
You can't do this in C/C++ legally:
vector3::operator float*() const
{
float arr[3];
// ...
return arr;
}
It invokes undefined behavior. When operator float*() returns, arr goes out of scope and the pointer returned becomes invalid.
Consider yourself lucky, that you've got no nasal demons ;-)
answered Nov 21 at 11:33
datenwolf
132k10131234
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member functionglvertexthat internally calls glVertex.
– datenwolf
Nov 22 at 7:34
add a comment |
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You can't do this in C/C++ legally:
vector3::operator float*() const
{
float arr[3];
// ...
return arr;
}
It invokes undefined behavior. When operator float*() returns, arr goes out of scope and the pointer returned becomes invalid.
Consider yourself lucky, that you've got no nasal demons ;-)
answered Nov 21 at 11:33
datenwolf
132k10131234
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member functionglvertexthat internally calls glVertex.
– datenwolf
Nov 22 at 7:34
add a comment |
2
You can't do this in C/C++ legally:
vector3::operator float*() const
{
float arr[3];
// ...
return arr;
}
It invokes undefined behavior. When operator float*() returns, arr goes out of scope and the pointer returned becomes invalid.
Consider yourself lucky, that you've got no nasal demons ;-)
answered Nov 21 at 11:33
datenwolf
132k10131234
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member functionglvertexthat internally calls glVertex.
– datenwolf
Nov 22 at 7:34
add a comment |
2
2
2
You can't do this in C/C++ legally:
vector3::operator float*() const
{
float arr[3];
// ...
return arr;
}
It invokes undefined behavior. When operator float*() returns, arr goes out of scope and the pointer returned becomes invalid.
Consider yourself lucky, that you've got no nasal demons ;-)
answered Nov 21 at 11:33
datenwolf
132k10131234
You can't do this in C/C++ legally:
vector3::operator float*() const
{
float arr[3];
// ...
return arr;
}
It invokes undefined behavior. When operator float*() returns, arr goes out of scope and the pointer returned becomes invalid.
Consider yourself lucky, that you've got no nasal demons ;-)
answered Nov 21 at 11:33
datenwolf
132k10131234
edited Nov 21 at 14:53
answered Nov 21 at 11:33
datenwolf
132k10131234
answered Nov 21 at 11:33
datenwolf
132k10131234
answered Nov 21 at 11:33
datenwolf
132k10131234
132k10131234
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member functionglvertexthat internally calls glVertex.
– datenwolf
Nov 22 at 7:34
add a comment |
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member functionglvertexthat internally calls glVertex.
– datenwolf
Nov 22 at 7:34
So what should I do?
– jinenofu
Nov 22 at 0:05
So what should I do?
– jinenofu
Nov 22 at 0:05
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
For one (that's OpenGL related): Don't use immediate mode (anything that makes use of glBegin/glEnd). It's outdated for over 20 years. But if you really want to go down that road and insist on using the …v versions, then put your x, y, z members at contiguous locations in your class, or use an array there and return a pointer to that. However this will require, that you don't use that pointer, when the class instance goes out of scope.
– datenwolf
Nov 22 at 7:33
@jinenofu: You could also introduce a new class member function
glvertex that internally calls glVertex.– datenwolf
Nov 22 at 7:34
@jinenofu: You could also introduce a new class member function
glvertex that internally calls glVertex.– datenwolf
Nov 22 at 7:34
add a comment |
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Hi @jinenofu please provide a Minimum, Complete and Verifiable example see: stackoverflow.com/help/mcve
– AdaRaider
Nov 21 at 5:51
4
float arr[3];is a local variable in a method. You return a pointer to local data. The data go out of scope (are lost) after the function has terminated. Read a basic C++ or C tutorial.– Rabbid76
Nov 21 at 5:55
What is
origin?glVertex3fvexpects a pointer to 3 contiguousGLfloats. Are you sure thatoriginhas a type which grants this? What type does it actually have?– Scheff
Nov 21 at 7:18
I assume, you want to call
glVertexfor your DIY typevector3? How about an "overload"? E.g.void glVertex(const vector3 &v) { glVertex3f(v.x, v.y, v.z); }Then, you could do e.g.vector3 origin(1, 2, 3); glVertex(origin);. (I made some assumptions about your code but I guess you got the idea.)– Scheff
Nov 21 at 7:21
This is a C++ problem, not an OpenGL one. You're returning an address to a temporary. UB. Without seeing the sources of
vector3it's hard to answer definitely, but the recommendation I'd give is the same - ditch your own class and just use GLM. There are apparently more ways to write a vec3 badly than to do it correctly.– Bartek Banachewicz
Nov 21 at 8:49