How to move a particular texture around screen in android using opengl es ?

Question

Hi, I am very new to OpenGL ES. I am implementing some demo app to load multiple textures on the screen. For demo purpose I have loaded 2 textures in 2 different locations on the screen using glTranslatef() and glBindTextures() twice.

Now I am able to see 2 different images on the screen. Now I want to move one particular texture across the screen using mouse.

I know it may be silly topic, but please help me in this..

Thanks in advance..

Answer 1

Hi,

You don't actually want to move the texture, but either you move your Scene point of view ( gluortho2d / glulookat / gltranslatef - or anything else ), or you move the vertices of the shape you're applying your texture to.

this is how im doing it in my 2D game :

gl.glTranslatef(-cameraPosX % 32, -cameraPosY % 32, 0);

Answer 2

As mentioned above you will need to translate the coordinates of the surface.

If you are using orthagonal (2D) projection, the pixel/coord ratio can be set to 1:1 easily by defining the projection to be the same size as the screen. For example:

 glOrthof(0.0f, screenWidth, -screenHeight, 0.0f, -1.0f, 1.0f);

should define a projection with (0,0) in the top left and the same size as your screen.

If you are using 3D projection, you may find this link helpful: http://www.mvps.org/directx/articles/rayproj.htm