Specular uses the same 8-bit factor expansion as diffuse, and attenuation
(with the spot factor) is a second 8-bit factor applied after it, also to
ambient. Exact on gpu/probe exp63 for specular, 99.5% for point lights (the
attenuation's own precision is not matched).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The light and material colors first make an 8-bit product, and N.L becomes an
8-bit s = floor(256 * f), which is expanded like a color before the second
multiply: ((2x + 1) * (2s + 1)) >> 10. Bit exact on gpu/probe exp61-62, apart
from N.L itself being about 2^-15 high on the PSP with a scaled world matrix.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Environment map S and T are (N.L + 1) / 2 with L the light's vector as
lighting uses it: from the vertex to the light for point and spot lights,
a zero vector staying zero, and the half vector for a light that does
specular. Whether lighting or the light is enabled still doesn't matter
(gpu/lighting/shademap).
The vertex shader ID now carries the type and computation of the shade
mapping lights (the ubershader reads them from u_lightControl), so both
shader caches get a new version.
Fixes the hair shine in iDOLM@STER SP (#12376).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The viewer is at infinity along view space +z, so in world space, where
lighting happens, it's the view matrix's third column rather than
(0,0,1): turning the camera moves the highlights (gpu/lighting/specular).
The shaders read it from u_view.
In a Need for Speed Carbon frame replayed on a PSP, this and the pow
bring the error of the cars from MSE 957 to 120 (Vulkan).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The GE computes these powers as exp2(e * log2(x)), with log2 and exp2
each a straight line between powers of two (Mitchell's approximation),
and only uses the top 4 bits of the specular coefficient's mantissa.
Through a highlight's falloff a true pow is 10-30 steps of 255 brighter
at the exponents games use. Measured in gpu/lighting/specular.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
In many cases, games use lighting just for diffuse or something, this
helps skip what's not needed too. Good improvement in a scene from a
Naruto game.
This seems to be a bit more accurate. Color blending seems correct now,
but the factors and especially pow results are off.
Also, normalize normal to 0, 0, 1, which seems to match results better.
This is correct per hardware tests, see #8403. Note that the PS3 emulator
running PSP HD remasters does not correctly handle this, and applies
specular for negative diffuse factor.
