Libgdx - Texutre masking

Newbie & Debugging Questions
#1

Hello.

I have 2 images.

The first is my base image. It will be loaded to TextureRegion. So, lets make assumption i have it loaded for variable;


TextureReguion koala = ...;

I don’t want draw entire image, but only pixel who cover black pixels in my shape.png image. But this may not be persist change. In future i want just take off the mask and draw entire picture. Format of mask is flexible. This is only example. I can use anyone.
Can You write few line of code which can do this and draw masked texture on SpriteBatch?

#2

not sure, do ask in the libgdx forum !

http://www.badlogicgames.com/forum/

#3

Use a shader. Sample the first texture, sample the second texture, multiply them together. Well, since your mask texture is black where you want the other texture to be seen, I suppose you’d have to invert the value of the mask texture before doing the multiply though.

#4

Check out my tutorial series. One of the lessons includes a very similar effect.

[icode]config.useGL20 = true;[/icode] must be set when creating the activity
[icode]isGL20Available()[/icode] must return true

If you want the masking to work on GLES10, you’ll need to tinker with texture combiners and blend modes.

#5

Uhm, this seems like a thing to do with blending, for example (find the suitable)

800×600 73 KB

Unless there is some more to it.

davedes’ shader tutorial is very well written though. Should read that too

#6

Shaders is pretty hard to newbe i think. But i found information this is dooable with stencil test. Unluckly any of my try to do this faild. Can you write simple example code using this method?

#7

To use the stencil test for this effect (without shaders), you’d have to render the mask texture as geometry (= a 5 vertex polygon creating a pentagon), not a rectangular textured quad with a texture of a pentagon. However, if you do that there’s nothing stopping you from completely getting rid of the extra pass, since you can just directly put the koala texture on your 5 vertex polygon.

#8

See http://nehe.gamedev.net/tutorial/masking/15006/ for a non-shader implementation.

Everything in OpenGL is hard for a newby, but learning how to use shaders in the first place saves you a ton of other hard stuff you won’t need anyway as soon as you are capable of using shaders…

Take your time and read http://wiki.labomedia.org/images/1/10/Orange_Book_-_OpenGL_Shading_Language_2nd_Edition.pdf, at least Chapters 4,5,9 and 10, but best the whole book.

Don’t whine about it being 600+ pages - the book will save you much more time than you will spend reading it. :stuck_out_tongue: