Translation in opengles

Question

1. I translate the modelview matrix to: glTranslatef(-camerax, -cameray, -cameraz)
2. rotate the modelview matrix to camera rotation glRotatef(camangle, camrotx, camroty, camrotz)

3. Then i render the objects starting here between pushmatrix & popmatrix commands.

   Everything working, translating and rotating well. Until i try to move camera in the rotated modelview matrix. I want to translate the camera moves toward (int its own object space).

4. I added this line into onKeyDown method of UP key: glTranslatef(0f, 0f, 1f);

But with this command, the cam moves toward -z axis of modelview matrix, not toward -z axis of its own space.

I could not figure out how to make the object translation in its own toward direction. Can somebody explain me how it shoud be done.

Answer 1

posz += (zdif * (float)(Math.cos(Math.toRadians(yrot))));
glTranslatef(0f, 0f, posz);

did make the necessary translation.

Answer 2

It's all about multiplication order (as matrix multiplication is not commutative). It makes a big difference do step 4 before or after step 2! One is in screen space, the other is world space.