Webgl doesn't support BGRA textures, so this lets us use
Stage3D textures on the web backend. As a bonus, this speeds up
uploading an BitmapData to a Context3dTextureFormat.BGRA texture,
since we no longer need to change the format before copying.
This makes Solarmax2 playable on the web backend.
This is a very large diff, but most of it comes from test files and
output.
This PR ads partial support for the following Stage3D shader features:
* Normal (square), rectangle, and cube textures
* Varying and temporary registers
* Lots of opcodes
The combination of these allows us to get a raytracing program
fully working in Ruffle. I've included it as image test.
Currently, this test is very slow (about 90 seconds on my machine),
as the code I'm using (https://github.com/saharan/OGSL) includes
its own shader language and compiler. THe raytracing demo
first compiles its own shader language to AGAL, and then starts
rendering the scene.
Limitations:
* Many opcodes are still unimplemented
* Most non-default texture options (e.g. mipmaps) are not implemented
When rendering to an offscreen texture for `Bitmapdata.draw`,
we first render to a temporary frame buffer, and then copy the contents
of the frame buffer back to the target texture. However, this results
in blend modes being incorrectly applied - for example, rendering with
BlendMode.SUBTRACT will subtract against the framebuffer (which starts
with each pixel as 0x00000000), instead of the previous BitmapData
contents.
To fix this, we now use our texture target as the frame buffer
when performing `render_offscreen`. This ensure that we blend
over existing pixels (taking into account the `blendMode` provided
in the `BitmapData.draw` call).
When multisampling is enabled, we use a copy pipeline to copy
the existing contents of our texture to a fresh multisampled frame
buffer (the non-multisampled texture target becomes our resolve buffer).
Aaron Hill