NeHe OpenGL Lesson42 - Multiple Viewports

    This samples shows us how to create multiple views in one window. With OpenGL command glViewport, we could place our scene into any rectangle area on the window. Usually, we will set the view port to the size of the window or window client area. This will make one full window view display. With glviewport function, you could choose any rectangle area on a window to display your view. This command will take the left-bottom point as the original point, width goes along horizontally, and height goes along vertically.

 

 

 

Update OpenGL texture object dynamically

// tex_data contain RGB texture data
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, tex_data);

 

Create the maze texture data

Once you play a bit with the program, you will be curious about such maze texture created. Here is the main workflow:

1. a) At first, we will choose a random position (2i, 2j) as the start point;
2. b) Check all position at (2i, 2j) are filled with color, if all of them are filled with color, then the process finished, otherwise continue;
   c) Check current position (2i, 2j) is a validate position (this position will not beyond the rectangle area and could turn around: could turn up or down, left or right ). If this is validate position, continue; otherwise, use a while loop to randomly pick up an empty position (2i, 2j); continue;
   d) randomly find a turn direction; filled with the new direction { 4 possibility, (2i+1, 2j), (2i-1, 2j), (2i, 2j+1), (2i, 2j-1) }if we could turn along this direction, and move the position to a new position (2n, 2m) { 4 possibility, (2i+2, 2j), (2i-2, 2j), (2i, 2j+2), (2i, 2j-2)};
   e) fill color to (2n, 2m);
   f) go to step b).

   maze image	maze image without shading turn direction

 

The full source code could be found here.