VR requires glDrawBuffer, which Mesa OpenGL ES does not offer. Default
VR to disabled for OpenGL ES users. Users who want to try it anyway can
still set use_stereo_render=1 in the SCons environment.
The preceding commit breaks OpenGLES + SDL1 support, by referencing
SDL_GL_* constants that are new in SDL2. Add a preprocessor guard to
skip over the new constants when using SDL1.
Fixes: c90ac3e611 ("Fix OpenGL ES build on SDL2.")
- Skip reading unused alpha channel in TGA screenshot path. The alpha
channel is discarded, so skip even retrieving it from OpenGL.
- Perform the red/blue swap in place, instead of copying into an
additional buffer.
This triggers a diagnostic from -Wuseless-cast. It appears to be
unnecessary, after tracing down typedefs. It might need to be restored
if some platform uses a definition that is neither the same type nor
implicitly convertible.
gr_find_closest_color did not need it. Remove it. For the others,
resetting the count is sufficient. There is no need to reset the
individual elements.
The fallthrough appears to be intentional. Add an annotation to allow
it.
Fixes: 6bc0e822d2 ("Handle HUD overlays in separate screen rects for stereo renderings.")
Note since ogl_stereo_frame() is only ever called once per ogl_start_frame()..
ogl_end_frame() instance, only the active stereo eye view needs to be handled.
Implies that separate left/right viewport/transform caches are redundant.
Equivalent to legacy Descent 1.5 pixel shift methods for stereo formats.
Since Descent is rendering viewpoint differences for left/right eyes,
pixel shifting via display viewport is sufficient adjustment.
Since OGL layer here is essentially handling display output surfaces,
the OGL projection transform is not useful for stereo parallax effects
as when used for 3D scenes.
Enable stereo mode when launched via -gl_stereo option.
GL_STEREO quad buffering may not be available unless OGL layer
supports stereo pixel format descriptors.
Half-height viewport rendering for above/below format.
Half-width viewport rendering for side/by/side formats.
HUD & cockpit elements disabled when stereo views active.
OGL layer used for rendering surfaces, so using left/right viewports absent stereo quad buffers.
Using legacy Descent +/- eye offset method for left/right stereo perspective rendering passes.
