Alpha mapping is a technique in 3D computer graphics where an image is mapped (assigned) to a 3D object, and designates certain areas of the object to be transparent or translucent. The transparency can vary in strength, based on the image texture, which can be greyscale, or the alpha channel of an RGBA image texture.
1-Hello everyone, in this lesson we will talk about alpha maps, alpha maps are really important cause they are helpfull to create very detailed or photo realistic result in 3d from leaves for a plant or tree to character’s hair for video games.
So basically there is one rule that says : White is visible – Black is invisible (transparent).
We will start with a leave image in photoshop to understand an Alpha map, simply search google to find any of your choice:
2 – Lets press F7 on keyboard to open up layers window and double click on our image (name background) and press Ok; this will convert that to a layer.
3- Select magic wand tool and change the tolerance to 25, click on white area and press Delete key on your keyboard. Select magic wand tool again and click out of the screen to deselect that area.
4- So now we have a transparent leaf image in photoshop, its time to make the background green, so if any pixel fails in our alpha map, that will have the same color of our leaf and its not going to be noticable . Create a new layer, select eye dropper tool, click anywhere off leaf, then select paint bucket tool and fill that layer by clicking in our image. Don’t forget to drag our green layer under the leaf layer.
5- Select move tool, Press control-T on your keyboard and rotate the leaf a bit to get a better direction. When you are done, press enter on your keyboard.
6- Press filter menu and click in sharpen—> sharpen mask and change the values as follows, this will help us to made our leaf image sharper and better in quality to prevent blur (you can change the values as its based on your image, so play with the percentages).
7- Now its time to save our image as a jpg file. A quality of 10 would have a balance of quality and file size. Also save a PSD file just in case you want to edit something later.
8- Select the green background, select a black color and fill the background layer using paint bucket tool.
9- Select the leaf layer, click on FX icon and click color overlay.
10- Select a pure white color and click OK .
11- Now save this image as our alpha-map, also click on image—>image size and remember to write the size of our image in pixels.
12- Open your 3d software, in our case its 3ds max, and create a plane the same size as your image size. Dont worry if it looks too big, you can always scale it down.
13- Now press M to open material editor, select a material, add the leaf image we created in photoshop as diffuse and add the alpha image as opacity. Also check two sided box.
14- Make sure the plane is selected then press “assign material to selection” and “show standard map in viewport”.
15. Now we simply finished to get a working alpha map in our 3ds max software. By adding more segments to our plan and moving them around or adding a bend modifier, we can create a good result that we can use on our models.
I hope you enjoyed using this method, please dont hesitate to ask if you have any other questions. Don’t forget to check out the other tutorials in our Texturing section, and if you’d like more information on this technique have a look at our older alpha map tutorial.
Happy alpha mapping!