Use glDrawArraysInstancedBaseInstance() to draw. (Yay for GL naming.)
That allows setting up the offset in the vertex array without having to
glVertexAttribPointer() everything again.
However, this is only supported since GL 4.2 and not at all in stock GLES,
so we need to have code that can work without it.
Fortunately, it is mandatory in Vulkan, so every recent GPU supports it.
And if that GPU has a proper driver, it will also expose the GL extension
for it.
(Hint: You can check https://opengles.gpuinfo.org/listextensions.php for
how many proper drivers exist outside of Mesa.)
The env var allows skipping various optimizations in the GPU shader.
This is useful for testing during development when trying to figure
out how to make a renderer as fast as possible.
We could also use it to enable/disable optimizations depending on GL
version or so, but I didn't think about that too much yet.
When drawing opaque color regions that are large enough, use
vkCmdClearAttachments()/glClear() instead of a shader. This speeds up
background rendering on particular on older GPUs.
See the commit messages of
bb2cd7225ece042f7ba10edd7547c1
for a further discussion of performance impacts.
The previous algorithm would reverse the order of subpasses, whcih leads
to unexpected behavior if dependent subpasses are not added as children
of a subpass, but just as a previous subpass - like when a subpass is
used multiple times later.
An example for this is a shadow node with multiple shadows - the source
of the shadow is used by the multiple shadows.
So ensure that adjacent subpasses stay in the same order.
The code generated by glslc -O is optimized worse by Mesa than
code generated unoptimized.
So generate unoptimized code until somebody figures out what's going
wrong here.
They're done using the pattern shader.
The pattern shader now gained a stack where vec4's can be pushed and
popped back later, which allows storing the position before computing
the new position inside the repeat node's child.
Due to GLES and old GL not allowing non-constant texture array
lookups,we need to turn the array lookup into a big switch statementin
those versions, and that requires putting the texture() call into that
switch.
But with that trick, we can use texture IDs in GLSL.
... and use it for glyphs.
The name is a slight variation of the "coloring" name from the GL
renderer.
The functionality is exactly what the "glyph" shader from the Vulkan
renderer does.
1. Compute the fwidth() twice with offset offsets
That way, we avoid glitches at the boundary between 0.0 and 1.0,
because by offsetting it by 0.5, that boundary goes away.
Then we take the min() of both which gives us the one we care about.
2. Set the gradient to repeating
By doing that, we don't get values at the 0.0/1.0 boundary clamped,
but things smoothly transition.
This smoothes the line at that boundary and makes it look just like
every other line.
Instead of strictly rounding to the given clip rectangle, increase the
rectangle to the next pixel boundary.
Also add docs that the clip_bounds do not influence the actual size of
the returned image.
It's just an object that encapsulates everything needed to create (the
data for) a pattern op.
It also clarifies which code does what, because now the NodeProcessor
and the PatternWriter are 2 different things.
Pretty much a copy of the Vulkan border shader.
A notable change is that the input arguments are changed, because GL
gets confused if you put a mat4 at the end.
when doing get_node_as_image(), that may spawn a new buffer writer that
writes into the samme buffer when rendering an offscreen with patterns.
So as a more or less hacky workaround, we now abort the current buffer
write and restart it once we've created the image.
If creation fails, create an offscreen image instead and draw that as a
texture.
Because offscreens basically always succeed, we can pretty much assume
success everywhere - apart from pattern creation functions that also
create images, because they can run out of shader space.
Frames now carry a timestamp for when they are used.
This is mainly intended to attach timestamps to cached items (textures
or glyphs), but it could in theory also be used when profiling.
We use wallclock time here, not server time, because it's cheaper and
because we're more intereseted in the local machine we're rendering on.
Now we can extend the pattern creation easily - and we can add new
patterns quickly later.
Plus, we need to keep this file in sync with pattern.glsl and it's neat
when those 2 files reference only each other.
Because GL flips its shit sometimes (ie when it's the framebuffer),
pass the height of the target as the flip variable, so commands
that need to operate on the pixels can flip the y axis around this value.
This is again mostly a copy of the Vulkan renderer.
It's a bit awkward codewise with the new invalidation framework,
because we need to cache the previous values individually now,
but it's a lot more finegrained, and we don't emit globals multiple
times when clips are nested.
... and use it to initialize the "proper" projection matrix to use in
shaders.
The resulting viewport will go from top left (0,0) to bottom right
(width, height) and the z clipping plane will go from -10000 to 10000.
