This adds a new texture memory allocation header,
texture_memory_alloc2.hpp, with two of each memory area.
This also adds two new examples, "cube_textured" and "cube_vq" that
demonstrate using the new texture_memory_alloc2 to perform CORE
rendering, geometry transformation, and tile acceleration
concurrently.
The previous texture_memory_alloc.hpp was written based on an
incorrect understanding of the "32-bit" and "64-bit" texture memory
address mapping.
The primary motivation is to rearrange the texture memory address map
so that "textures" (64-bit access) do not overlap with 32-bit
accesses, such as REGION_BASE or PARAM_BASE.
The main issue with the previous code:
constexpr uint32_t tiles = (640 / 32) * (320 / 32);
Should have been:
constexpr uint32_t tiles = (640 / 32) * (480 / 32);
The consequence of this is some OPBs were being overwritten by
TA_NEXT_OPB, causing corruption (missing triangles, incomplete
drawings) in some tiles.
This enables alpha blending for both font_outline and
font_outline_punch_through.
I have also experimented more with 16-gray vs 256-gray--I have not
decided which between monochrome, 16-gray, or 256-gray I like the
most.
Perhaps a better test might be to test hanzi.
This draws a nice macaw texture in a square-shaped triangle
strip. The square is then rotated around the y-axis.
I dealt with myriad bugs while experimenting with this, all of them
entirely my fault:
- macaw texture colors were incorrect because GIMP was exporting raw
RGB data in gamma-corrected sRGB space, whereas the Dreamcast is in
linear color space.
- macaw texture colors were incorrect because I truncated color values
to the least significant rather than most significant bits.
- macaw rotation around the Y axis caused the macaw texture to
distort, stretch and recurse in interesting and unexpected ways. This
was caused by sending Z values in the wrong coordinate space (Z)
contrast to what is expected by the Dreamcast (1/z). Reordering
z-coordinate operations so that the reciprocal is computed last
resolved this.
- macaw rotation around the Y axis caused the macaw texture to warp
unexpectedly, but only on real hardware. This was caused by
unnecessarily negating Z coordinate values.
Behavior for each of the Z-coordinate issues differed between Flycast
and real Dreamcast hardware.
I also did several tests related to SH4 cache behavior, particularly
related to the "copy-back" mode. I verified copy-back behavior on a
real dreamcast, and experimented with the operand cache write-back
instruction, "ocbwb".
In particular, when the `scene` buffer is access from cacheable
memory, e.g: the P1 area, and CCR__CB is enabled, DMA from physical
memory to the TA FIFO polygon converter will fail because the scene
data has not yet been written to physical memory yet. `ocbwb` can be
used to "write back" scene from the SH4 operand cache to physical
memory--only the latter is visible from the CH2-DMA perspective.
This rearranges scene.cpp to a file organization that more closely
follows which code is responsible for what area of (hardware)
initialization.
All TA and CORE register accesses now use the new ta_bits.h and
core_bits.h, respectively.
