On 7/24/06, Jason Green <[EMAIL PROTECTED]> wrote:
I've spent a couple of days researching the issue of broken/upside-down character/object models in Wine in almost all newer games when you have vertex shaders enabled (Civ4, Half Life 2, Oblivion, Max Payne 2, etc.).
Yes, I remember some talk on IRC, and wanted to comment, but will do now.
I think I've boiled it down to a single case: When "device->renderUpsideDown" is set in the case where vertex shaders are enabled. That flag gets set in device.c:7395 when the current renderTarget is not on the current swapchain. The comments in the source say that the upside-downedness is produced by glCopyTexImage, so it sets a flag to flip everything over. In the case w/o shaders, there is code in drawprim.c which loads the WORLDVIEW and PROJECTION matrices and then multiplies those matrices by one which inverts the y coordinates when that flag is set. That seems to work in the case without vertex shaders, but when shaders are enabled, they bypass the WORLD, VIEW, and PROJECTION matrices entirely. The shader case was written when only software shaders worked, but that is no longer true. It loads identity matrices and performs the y flip, but that code is entirely irrelevant since the vertex shader doesn't reference those matrices; it only uses constants that are passed by the app, which we can't perform any type of fixup on since we don't know which constants will be used for which calculation.
Yeah, I've noticed all this with Star Wars Battlefront. See bug 5247. Without vertex shaders, I have a very simple hack to fix the one issue of an upside down skybox. What I did should be quite obvious to you. With vertex shaders (note: I make brief mention in bug comments about how to get them working with dri, you might remember this from IRC too) having them enabled, the problem gets a little worse as certain parts of the skybox are correctly up and others upside down. If you apply the hack, then *everything* got flipped -- those that were correct were now upside down, and vice-versa. Also parts of the box got shifted a bit. This is with ARB shaders BTW. I'll post screen shots when I get the chance. I wonder if there was a reason for the flip code because it does flip some things correctly.
So, I think what we need to do is prevent ourselves from having to do any flipping whatsoever. That's the part that I'm not sure how to do and is the reason for this email.
That I'd agree with. There are certainly things it does wrong. But I think I need to go back studying the code before I make any recommendations. :) I'll try to get back to you later. Jesse
