CSC 240: Computer Graphics

Lab 13: Texture Mapping

The goal of this lab is to become familiar with using textures in OpenGL. It will probably be our last OpenGL lab!

Note: this lab will not be graded, but it will help us get ready for the last OpenGL homework.

  1. Download the textures here and put them in the same folder as the lab code. If you have Pillow, use the "jpg" files, and if you don't, use the "txt" files (no difference in the images you will get).

    apple.jpg
    wood.jpg
    sky.jpg
    wallpaper.jpg
    grass.jpg

    Right-click and choose "Save Link As...":

    apple.txt
    wood.txt
    sky.txt
    wallpaper.txt
    grass.txt

  2. If you have Pillow installed, download lab11_PIL.py and make sure you can run 
    python lab11_PIL.py
    If you don't have Pillow installed, download lab13.py and make sure you can run 
    python lab13.py
    You can check if you have Pillow by running 
    from PIL import Image
    You should see something like this:

    apple1

    Look at the code where the texture is mapped to the vertices. Why is the apple upside down? (Hint: the image file is similar to a PPM in raster... where is (0,0)? ) Remap the texture to turn it rightside up.

  3. In the previous case, we were mapping a rectangular texture to a rectangular region, but what if the region had fewer sides? Comment out the rectangular regions and comment in the triangle. How should this be texture mapped? Does the following image look right (minus the apple being upside down)? There is no right answer to this question, it's up to the designer how to map these types of regions.

    apple2

  4. What about a case where the region has more sides? Comment out the triangle and comment in the octagon. Can you use the for loop to texture map these vertices to get something like this?

    apple3

  5. Now we are ready to start creating a "room" or "scene". First make the "floor" as shown below. You may need some transformations in addition to the translate to make your scene visible.

    apple4

  6. Then create the "walls":

    apple5

  7. Usually we want to "tile" the textures instead of using one image for a large region. To do this, instead of specifying the texture coordinates as 0-1, we can use higher numbers! Change this in the code, maybe try 3 copies for each dimension. What do you notice?

    In addition, we need to change the texture parameters from GL_CLAMP to GL_REPEAT. Change this in the code as well to get a picture like the one below:

    apple6

  8. Finally, create something a bit more realistic, using any combination of the textures available (or download your own, but make sure it is small). Here is an example using wood floors and wallpaper to create rooms.

    apple7

  9. Maybe it looks a little better if we repeat the wall paper a bit more. The top and bottom edges match up, but the sides don't. Can you modify the wallpaper image to make it look better?

    apple8

BONUS 1: use roughly 30 GL_QUADS to create a cylindrical "tin can", and texture map this can using a rectangular image of your choice.

BONUS 2: find or create your own image textures (jpg is often best) and use them to create a "room".