Phong's stupid questions: Alpha blending from scratch

Game Engine Game Engine Support and Discussion
1

Okay. I spent way too much time trying to recreate the alpha blending game engine demo. I figure I might be able to save someone else a few minutes. Here goes:

  1. Create two PNG files. The first file is solid with no erased parts. The second file is partially erased. Don’t use the same picture. (Hey, this is Phong’s stupid questions after all…)

  2. Open Blender. Let’s say you left the default file as is and the default cube is selected. Do so if it’s not.

  3. In the 3D view, change to “UV Face Select” mode and immediately switch back to “Object mode”. (This gives every face default UVs) Switch the “Viewport Shading” to “Textured”.

  4. Click on the “Game” menu at the top of the screen and choose “Use Blender Materials”.

  5. Click “Shading buttons” or press F5.

  6. Click the "“Mirror Transp” tab. Press the “ZTransp” button.

  7. Click the “Texture” tab. Add another texture by pressing the empty button under the button that says “Tex”. Press the “Add New” button.

  8. Click “Texture buttons” or press F6.

  9. In the Texture tab, the second “Tex” button from the top should still be selected. Click on “Texture Type” and choose “Image”. Should open up an “Image” tab.

  10. Click “Load Image” and select the first image. That’s the solid one.

  11. Click the top most “Tex” button. Select “Image” under “Texture Type” and “Load Image” the second image. That’s the one you partially erased.

  12. Click “Material buttons”.

  13. In the “Texture” tab, the upper most “Tex” button is still selected. Click on the “Map To” tab.

  14. Click once on the “Alpha” button.

  15. Click on the “Texture” tab again.

  16. Here is the important bit. Click the second from the top “Tex” button. You’re selecting the solid image here. Click the “Map To” tab again. Find the “Texture blending mode” button. That’s the one that says “Mix” default. Choose “Multiply”.

  17. In the “Material” tab, click “Shadeless”. This is so we can look at the alpha transparency over the entire object without worrying about it being lit.

  18. Press “p”. Viola.

I’m not sure if this is a limitation but partial transparencies don’t seem to work for me. That is to say, if I parts of the image is “half” erased in a paint program, in Blender that part shows as solid where as parts that were completely erased show as holes.