power_play/src/kernel/kernel_shade.knl
2025-07-31 20:26:47 -05:00

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#include "kernel.h"
ConstantBuffer<K_ShadeSig> sig : register(b0);
/* ========================== *
* Lighting
* ========================== */
#define SAMPLES 16
#define MARCHES 16
#define EDGE_FALLOFF 100
float rand_angle(uint2 pos, u32 ray_index) {
Texture3D<u32> noise_tex = GpuResourceFromUrid(K_BLUE_NOISE_TEX_ID);
Vec3I32 noise_coord = Vec3I32(1, 1, 1);
noise_coord += Vec3I32(pos.xy, ray_index);
noise_coord.xyz += sig.frame_seed.xyz;
// noise_coord.xy -= sig.camera_offset;
u32 noise = noise_tex[noise_coord % uint3(K_BLUE_NOISE_TEX_WIDTH, K_BLUE_NOISE_TEX_HEIGHT, K_BLUE_NOISE_TEX_DEPTH)];
return ((float)noise / (float)0xFFFF) * Tau;
}
Vec3 get_light_in_dir(uint2 ray_start, Vec2 ray_dir)
{
Texture2D<uint2> flood_tex = GpuResourceFromUrid(sig.emittance_flood_tex_urid);
Texture2D<Vec4> emittance_tex = GpuResourceFromUrid(sig.emittance_tex_urid);
Vec3 result = Vec3(0, 0, 0);
Vec2 at_float = ray_start;
uint2 at_uint = ray_start;
for (u32 i = 0; i < MARCHES; ++i) {
uint2 flood = flood_tex[at_uint];
Vec2 dist_vec = at_float - (Vec2)flood;
float dist = length(dist_vec);
if (dist < 1) {
/* Scale light by distance from edge so that offscreen-lights fade in/out rather than popping in */
float dist_x = min(abs(sig.tex_width - at_float.x), at_float.x);
float dist_y = min(abs(sig.tex_height - at_float.y), at_float.y);
float dist_scale = min(min(dist_x, dist_y) / EDGE_FALLOFF, 1);
result = emittance_tex[flood].rgb * dist_scale;
break;
} else {
at_float += ray_dir * dist;
at_uint = round(at_float);
if (at_uint.x < 0 || at_uint.x >= sig.tex_width || at_uint.y < 0 || at_uint.y >= sig.tex_height) {
/* Ray hit edge of screen */
break;
}
}
}
return result;
}
Vec3 get_light_at_pos(uint2 pos)
{
Vec3 result = 0;
for (u32 i = 0; i < SAMPLES; ++i) {
float angle = rand_angle(pos, i);
Vec2 dir = Vec2(cos(angle), sin(angle));
Vec3 light_in_dir = get_light_in_dir(pos, dir);
result += light_in_dir;
}
result /= SAMPLES;
return result;
}
/* ========================== *
* Entry point
* ========================== */
Struct(CsInput)
{
Semantic(uint3, SV_DispatchThreadID);
};
[numthreads(8, 8, 1)]
K_ENTRY void cs(CsInput input)
{
uint2 id = input.SV_DispatchThreadID.xy;
if (id.x < sig.tex_width && id.y < sig.tex_height) {
Texture2D<Vec4> albedo_tex = GpuResourceFromUrid(sig.albedo_tex_urid);
Texture2D<Vec4> read_tex = GpuResourceFromUrid(sig.read_tex_urid);
RWTexture2D<Vec4> target_tex = GpuResourceFromUrid(sig.target_tex_urid);
Vec4 color = Vec4(1, 1, 1, 1);
/* Apply albedo */
color *= albedo_tex[id];
/* Apply lighting */
if (!(sig.flags & K_SHADE_FLAG_DISABLE_EFFECTS)) {
color.rgb *= get_light_at_pos(id);
}
/* Apply temporal accumulation */
float hysterisis = 0;
// hysterisis = 0.2;
// hysterisis = 0.4;
// hysterisis = 0.5;
// hysterisis = 0.9;
color.rgb = lerp(color.rgb, read_tex[id].rgb, hysterisis);
target_tex[id] = color;
}
}