Change color of mesh displayed by the function CGAL::draw() - cgal

Question

Problem descriptionI wonder if there is a way to change the color of mesh displayed by the function CGAL::draw(). I have a Surface_mesh, I want to draw it with CGAL. So I use the function CGAL::draw(), but the color of mesh is blue, which is not pretty in my view. I tried to change the code of CGAL to change the color. I found a functor called DefaultColorFunctorFaceGraph in a header file called draw_face_graoh.h, there is an annotation above the definition of DefaultColorFunctorFaceGraph, which says "// Default color functor; user can change it to have its own face color". I change the functor, in which I change the return value to CGAL::IO::gray(), but it doesn't work at all, the color of mesh is still blue.So can I change the color of mesh by changing the code of CGAL? Is it necessary to change lower level code such as some codes calling OpenGL?
Code
Here is an example about the way I use the function draw().
#include<iostream>
#include<fstream>
#include<CGAL/Surface_mesh.h>
#include<CGAL/draw_surface_mesh.h>
#include<CGAL/Exact_predicates_inexact_constructions_kernel.h>
typedef CGAL::Exact_predicates_inexact_constructions_kernel kernel;
typedef kernel::Point_3 point;
typedef CGAL::Surface_mesh<point> Mesh;
int main() {
std::ifstream fin("test.off");
Mesh mesh;
fin >> mesh;
CGAL::draw(mesh);
}
The file called test.off is as follws.
OFF
4 4 0
0 0 1
0 0 0
1 0 0
0 1 0
3 2 0 1
3 1 0 3
3 1 3 2
3 3 0 2
Here is the changed functor.
namespace CGAL
{
// Default color functor; user can change it to have its own face color
struct DefaultColorFunctorFaceGraph
{
template<typename Graph>
CGAL::IO::Color operator()(const Graph&,
typename boost::graph_traits<Graph>::face_descriptor fh) const
{
if (fh == boost::graph_traits<Graph>::null_face()) // use to get the mono color
//return CGAL::IO::Color(100,125,200); // R G B between 0-255
return CGAL::IO::gray();//Here changed
return get_random_color(CGAL::get_default_random());
}
};
Runtime environment
IDE: VS 2017
Solution configuration: Release x64
CGAL version: 5.3

Answer 1

Finally I found a struct named Basic_viewer_qt in a header file called Basic_viewer_qt.h. By changing the values of variables m_faces_mono_color and m_ambient_color in this struct, color of mesh can be changed.