[quake3-bugzilla] [Bug 6077] New: OpenGL2: Add r_ignoreDstAlpha

[bugzilla-daemon at icculus.org]

https://bugzilla.icculus.org/show_bug.cgi?id=6077

            Bug ID: 6077
           Summary: OpenGL2: Add r_ignoreDstAlpha
    Classification: Unclassified
           Product: ioquake3
           Version: GIT MASTER
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: minor
          Priority: P3
         Component: Video
          Assignee: zachary at ioquake.org
          Reporter: use.less01 at gmail.com
        QA Contact: quake3-bugzilla at icculus.org

OpenGL2 uses a RGBA16F framebuffer when rendering in HDR.  This was changed
from a RGB16F framebuffer because the former is 64bpp and four-byte aligned,
whereas the latter is 48bpp and not.  Not being four-byte aligned lead to
problems on certain hardware.

OpenGL1 doesn't require an alpha channel for its framebuffer, but certain
material shaders are written as if it did, utilizing GL_DST_ALPHA and
GL_ONE_MINUS_DST_ALPHA.

This lead to certain materials looking different between the two renderers.

This patch adds a cvar to OpenGL2, r_IgnoreDstAlpha, default 1.  When on, this
causes parsed material shaders to treat GL_DST_ALPHA and GL_ONE_MINUS_DST_ALPHA
as GL_ONE and GL_ZERO, respectively.  This reproduces the behaviour of having
no alpha channel in OpenGL2, and can be turned off if material shaders
expecting the alpha channel are used.

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