Hey guys,

I observe strange artifacts in my application when I switch from perspective projection

to orthographic projection.

Here's an image of the problem: https://dl.dropboxusercontent.com/u/56764397/projection_bug.png

It looks to me like some sort of z-fighting.

Now, I'm using depth peeling for transparency and the artifacts

disappear when rendering with another transparency technique,

so maybe the issue is how I read and write the depth textures.

It's pretty strange, though, because the projection matrix is not referenced in any fragment shaders.

Any ideas what I can do to isolate the problem?

Hmm. To my surprise the problem disappears when I choose a sufficiently large negative value for the near clipping plane.

So before I set (znear, zfar) = (0.1, 100.0) for both the perspective and the orthographic projection matrix and the error

occurs. When I choose (znear, zfar) = (-100.0, 100.0) for the orthographic matrix everything looks fine.

I have no idea why. Since setting znear = -100.0 essentially doubles the viewing volume I would guess the error

becomes even worse!

Could be gldepthfunc, try using GL_ALWAYS?