[SOLVED] Issue with glDepthMask

[kazade]

My game engine has a GL1 renderer which runs on both the PC, and Dreamcast which lets me compare behaviour between the two. I currently am trying to render a scene that does the following:

- glDepthMask(GL_FALSE);
- Render a textured background quad at z == 0
- glDepthMask(GL_TRUE);
- Render a textured cube at z == -5

On the PC this works as expected; I see a textured cube in front of the background.

On the Dreamcast (both emulator and on hardware) I just see the background.

Are there any known issues with glDepthMask? Anyone have any idea what the problem could be?

[kazade]

Bump...

I'm at a loss; I can't see anything obviously wrong with the libGL code.. yet that's where the problem must lie

[kazade]

Has anyone ever seen glDepthMask working? I've followed the code all the way down into KOS and everything looks fine, yet it definitely seems like depth writes are happening even when I've disabled them

[BlueCrab]

I'm not sure, as I've honestly never really worked with the current libgl at all.

That was pretty much all PH3NOM's thing, and unfortunately, he's not around maintaining it anymore.

[kazade]

BlueCrab, have you ever disabled depth writes with PVR commands directly? Looking at the code it seems that the depth.write flag is correctly set when compiling the polygon header - it just doesn't seem to work.

[BlueCrab]

Honestly, no, I haven't. I've never done any sort of 3D work at all on the Dreamcast, unfortunately.

Just a thought, but are either of the objects translucent or punch-throughs? If so, then they're possibly tripping up the automatic depth-sorting for translucent polygons that the hardware does unless you specifically disable it.

[kazade]

Yep it was down to the auto-sorting. I've disabled that now in my libGL fork so that the behaviour is more like traditional OpenGL.

[BlueCrab]

I'm glad to hear that solved the problem.