Could you post an entire sketch, including the obj, mtl and texture files, so I can run some tests? What do you exactly mean by the "textures not displaying correctly"?

Sure, I can do that.  I think possibly the texture is repeating, but processing is simply drawing it one time at some point on the object and instead of repeating the texture, it's drawing the edge of the texture all the way to the edge of whatever surface it's connected to.  But that's just speculation, I don't have any experience with 3D modelling.

Sketch file

1. float rotX, rotY;
   int sizeX,sizeY,middleX,middleY;
   PShape block;
   
   
   void setup()
   {
     sizeX = 800;
     sizeY = 800;
     middleX = sizeX/2;
     middleY = sizeY/2;   
     size(sizeX,sizeY,P3D); 
   
     block = loadShape("block.obj"); 
   }
   
   void draw()
   { 
     background(0); 
     lights();
    
     pushMatrix();
    
     translate(middleX-100, middleY, 0);
     rotateX(rotY);
     rotateY(rotX);   
     scale(100);
    
     shape(block);
   
     popMatrix();
    
   }
   
   void mouseDragged()
   {
       rotX += (mouseX - pmouseX) * 0.01;
       rotY -= (mouseY - pmouseY) * 0.01;
   }
   
   
   

Hi, thanks for posting the rest of the sketch and data files. I will be probably slow to respond during the next week, but I will try to look at it as soon as I can.

Thanks for the help.  I'm at a loss as to how to get it to work without manually describing every vertex.  Which isn't so bad for a simple cube, but would get difficult for a full 3d scene.

Tested and the answer is:

Wow, thanks a lot, it works perfectly now!