This is the vectorized version of `gl_tex_parameter`, which sets the
parameters of a texture's sampler. We currently only support one single
pname, `GL_TEXTURE_BORDER_COLOR`, which sets the border color of a texel
for if it is sampled outside of a mip-map's range.
This adds a virtual base class for GPU devices located in LibGPU.
The OpenGL context now only talks to this device agnostic interface.
Currently the device interface is simply a copy of the existing SoftGPU
interface to get things going :^)
We now support generating top-left submatrices from a `Gfx::Matrix`
and we move the normal transformation calculation into
`SoftGPU::Device`. No functional changes.
We were normalizing data read from vertex attribute pointers based on
their usage, but there is nothing written about this behavior in the
spec or in man pages.
When we implement `glVertexAttribPointer` however, the user can
optionally enable normalization per vertex attribute pointer. This
refactors the `VertexAttribPointer` to have a `normalize` field so we
can support that future implementation.
This merges GLContext and SoftwareGLContext into a single GLContext
class. Since the hardware abstraction is handled via the GPU device
interface we do not need the virtual base of GLContext anymore. All
context handling functionality from the old GLContext has been moved
into the new version. All methods in GLContext are now non virtual and
the class is marked as final.
In its current state, ScummVM seems to invoke these methods just after
destroying the current GL context. According to the OpenGL spec:
"Issuing GL commands when the program does not have a current
context results in undefined behavior, up to and including program
termination."
Our old behavior was to deref a `nullptr`, which isn't that great. For
now, protect these two methods. If other ports seem to misbehave as
well, we can always expand the check to other methods.
This is based mostly on Fabian "ryg" Giesen's 2011 blog series
"A trip through the Graphics Pipeline" and Scratchapixel's
"Rasterization: a Practical Implementation".
The rasterizer processes triangles in grid aligned 16x16 pixel blocks,
calculates barycentric coordinates and edge derivatives and interpolates
bilinearly across each block.
This will theoretically allow for better utilization of modern processor
features such as SMT and SIMD, as opposed to a classic scanline based
triangle rasterizer.
This serves as a starting point to get something on the screen.
In the future we might look into properly pipelining the main loop to
make the rasterizer more flexible, enabling us to enable/disable
certain features at the block rather than the pixel level.
This currently (obviously) doesn't support any actual 3D hardware,
hence all calls are done via software rendering.
Note that any modern constructs such as shaders are unsupported,
as this driver only implements Fixed Function Pipeline functionality.
The library is split into a base GLContext interface and a software
based renderer implementation of said interface. The global glXXX
functions serve as an OpenGL compatible c-style interface to the
currently bound context instance.
Co-authored-by: Stephan Unverwerth <s.unverwerth@gmx.de>
