This is a tutorial on how to make an alpha (transparency channel) texture of trees and other complicated shapes for use in Blender's game Engine.This tutorial assumes a basic understanding of The Gimp and is based (from what I remember)on someone else's tutorial.

Thanks Whoever You Are.

First up we will do the basic technique then advance to trees and other complicated shapes.Fire up The Gimp and open a similar shot to the one below(A Car would be suitable). We are going to make transparent windows using the alpha technique.

 

Using the rectangular select draw a rectangle where the windows are and bucket fill with a colour that is close to the most common colour in the background. It probably won't be purple :) (Use the feather edges option with a radius of 4-5).Repeat for all areas you want to be transparent using the same colour and flatten the image.You could just use the selected rectangles to copy but when you are dealing with complicated shapes the colour select technique is so much easier.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now use the select by colour tool with a tolerance of about 5 with antialiasing and feather edges selected and select, once,anywhere the purple is.Now.. invert the selection, copy and paste(ctrl c, ctrl v )without moving your mouse and open the layers dialogue

Add a new layer and make the original layer invisible.Your image should look something like the one below.You will notice the purple edges left over. I try to make my "fill" colour a light/sky blue as the subject is often outlined by the sky and it seems to give "blue screen"effect that disguises the edges a bit on other backgrounds.Feel free to experiment with the feather edge radius on rectangular select and the select by colour tolerance to reduce the edge colour effect.

 

 

 

 

 

 

 

 

 

 

 

 

 

Now save this image as a .tga to keep the alpha information and uvmap this texture onto your object making sure the alpha setting is enabled in the editing window (F9). Voila you should have windows or a least some holes.It is very easy to add a dirt or reflections layer before the final steps but you will have to fiddle with the colour select Tolerance to get an effective look.Go to the next page for trees etc.

 

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