White (maybe uncolored) OBJ in GLSL/C++

Question

Hi I'm working to create a space environment with a ship inside.But after the creation of the skybox (no errors) I put my ship inside but it hasnt colour. It's something like white-black

I did(modeled) the ship with OPENSCAD and after with MESHLAB I exported it into .OBJ format. I load it inside the source code but he hasn't the texture/colour . That my ship in Meshlab :

I need to know only I have to add something about color in the code or it's error in input. What this?

If you need I post the code, but if is somthing normal this error explain me, anyway I'm a little newbie in opengl, so be patient, thank you

EDIT :

Look my .obj file in windows:

And the same project in ubuntu :

What's this difference?

Anyway the openscad code :

module navicella(){
  $fn=100;  
    rotate([0,180,270]){
    union(){
         rotate([270,180,0]){   
              rotate([90,0,0])
                cylinder(50,7,10,center=true);

              intersection(){
               translate([0,-25,0])    
                sphere(10);  
               translate([0,-25,0])
                cube(19,center=true);    
              } 
              difference(){
               translate([0,35,0])
                cube([10,15,15],center=true);    
               translate([0,40,0])    
                sphere(13);
              }  

              translate([5,-10,0])rotate([90,0,70])  
                cube([35,1,15],center=true);
              translate([-2,0,0])rotate([90,0,95])  
                cube([50,1,10],center=true);

              translate([0,3,6])rotate([0,-15,90])  
                cube([40,1,20],center=true); 
              translate([0,3,-6])rotate([0,15,90])  
                cube([40,1,20],center=true); 

              translate([0,-35,0])rotate([90,0,0])
                cylinder(10,5,0,center=true);
              translate([0,20,0])rotate([0,90,0])  
                cube([45,1,2],center=true);
              translate([0,25,0]) rotate([90,0,0])
                cylinder(5,4,7,center=true); 
        }    
    }
}
}
navicella();

Answer 1

Looks like you have forgot to disable all used textures that are not used by your model. That is very common mistake (I do it all the time still today).

What is probably happening?

1. You rendered skybox or any object with textures

   So for example GL_CUBE_MAP and or GL_TEXTURE_2D are enabled. Now when you start rendering your mesh that does not contain texture the textures are still enabled. So for every fragment/pixel GL will always sample the last set texture coordinate from last binded texture in all of the enabled texture targets and combine color according to GL settings.

   So if you model does not contain texture coordinates GL will use the last set one. That is usually in corner area where black border is ... or you are just in some dark region of texture. Also if you unbind textures that only means you bind default texture 0 which is usually black.

   To test/remedy this just callglDisable(GL_....); for all previously used texture targets. If it helps you know where the problem is.

   Also if your object contains texture coordinates and texture is not loaded properly (like wrong file name/path) then the result is usually black.

2. Missing or negative normals while rendering with lighting enabled

   Does not looks like it but it could be also the reason. If your model has wrong or no normals then the lighting computation result in wrong lighting. If the object is always dark even if you rotate it the the normals are negated (facing the other way) and you should change the front face for lighting/material or negate the normals.

   If the color intensity is changing with rotation then your object has probably no normal and again the last set normal is used (from previous rendering). In such case either compute normals for the object (via cross product) or disable lighting for that object.