   FOVs and Ratio
  Hello, I have the following question. I was reading about horizontal FOV, vertical FOV and ratios to project a 3D object onto a 2D plane (screen). And knowing the equations I implemented them.* The view point is in the origin (x = 0.0, y = 0.0, z = 0.0).* The cube (object) is in the negative z (x = 0.0, y = 0.0, z = -700.0).* The field of view is 90 degrees./* Screen's size */int screen_width = 1280;int screen_height = 1024;/* Ratio: 5:4 (1280 / 1024) */double ratio = (double)screen_width / (double)screen_height;/* Angle used: 90 degrees = 1.57 rad. */double angle = 1.57;/* Planes used to calculate the distances */double plane_x = tan(angle / 2);double plane_y = tan(angle / 2) * ratio;/* Distances (adjacent side of the angle)   from the view point to the projection plane */double distance_x = (screen_width / 2) / plane_x;double distance_y = (screen_height / 2) / plane_y;The result was a cube in the middle of the screen but that wasn't a really cube because it was larger horizontally than vertically.And if I get the value for the plane_y variable without the ratio that is the same as the plane_x:double plane_y = tan(angle / 2);The result was a real cube.My question is if this result is correct (I suppose that's well) when do I need to use it? because, as I said before, the cube (object) is larger horizontally than vertically and I don't like it but I suppose the equations are correct to project the points and I always need to use them.Thanks,Dany   
  if youre using opengl see glViewport(..) make sure youre giving it the correct numbers.though with a perspective projection u will always have some distortion, try an orthogonal projection + if its still distorted then your viewport +/ projection matrices are wrong   ;  Thank you zedz. Well, I don't use OpenGL. I did routines like draw lines, draw triangles... and I'm studying the way to locate the projection plane to render the scene. My intention is generate a certain effect of perspective, but not like a fish eye. I know if the object is near to the edge of the screen, it appears with a bigger perspective than it's located in the middle of the screen. But that's by the projection plane's distance. So, that's the idea to find the distance using the FOV and the screen's size.Thanks.   