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use mediump precision for kernel4 colors and areas
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Improves kernel4 performance for a Gio scene from ~22ms to ~15ms.

Updates linebender#83

Signed-off-by: Elias Naur <[email protected]>
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@eliasnaur
eliasnaur committed Apr 19, 2021
1 parent ffdc620 commit 82e2348
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Showing 3 changed files with 28 additions and 27 deletions.
55 changes: 28 additions & 27 deletions piet-gpu/shader/kernel4.comp
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Original file line number Diff line number Diff line change
Expand Up @@ -22,45 +22,45 @@
#define CHUNK_DY (TILE_HEIGHT_PX / CHUNK_Y)
layout(local_size_x = CHUNK_DX, local_size_y = CHUNK_DY) in;

layout(set = 0, binding = 1) readonly buffer ConfigBuf {
layout(set = 0, binding = 1) restrict readonly buffer ConfigBuf {
Config conf;
};

layout(rgba8, set = 0, binding = 2) uniform writeonly image2D image;
layout(rgba8, set = 0, binding = 2) uniform restrict writeonly image2D image;

#ifdef ENABLE_IMAGE_INDICES
layout(rgba8, set = 0, binding = 3) uniform readonly image2D images[];
layout(rgba8, set = 0, binding = 3) uniform restrict readonly image2D images[];
#else
layout(rgba8, set = 0, binding = 3) uniform readonly image2D images[1];
layout(rgba8, set = 0, binding = 3) uniform restrict readonly image2D images[1];
#endif

#include "ptcl.h"
#include "tile.h"

vec3 tosRGB(vec3 rgb) {
mediump vec3 tosRGB(mediump vec3 rgb) {
bvec3 cutoff = greaterThanEqual(rgb, vec3(0.0031308));
vec3 below = vec3(12.92)*rgb;
vec3 above = vec3(1.055)*pow(rgb, vec3(0.41666)) - vec3(0.055);
mediump vec3 below = vec3(12.92)*rgb;
mediump vec3 above = vec3(1.055)*pow(rgb, vec3(0.41666)) - vec3(0.055);
return mix(below, above, cutoff);
}

vec3 fromsRGB(vec3 srgb) {
mediump vec3 fromsRGB(mediump vec3 srgb) {
// Formula from EXT_sRGB.
bvec3 cutoff = greaterThanEqual(srgb, vec3(0.04045));
vec3 below = srgb/vec3(12.92);
vec3 above = pow((srgb + vec3(0.055))/vec3(1.055), vec3(2.4));
mediump vec3 below = srgb/vec3(12.92);
mediump vec3 above = pow((srgb + vec3(0.055))/vec3(1.055), vec3(2.4));
return mix(below, above, cutoff);
}

// unpacksRGB unpacks a color in the sRGB color space to a vec4 in the linear color
// space.
vec4 unpacksRGB(uint srgba) {
vec4 color = unpackUnorm4x8(srgba).wzyx;
mediump vec4 unpacksRGB(uint srgba) {
mediump vec4 color = unpackUnorm4x8(srgba).wzyx;
return vec4(fromsRGB(color.rgb), color.a);
}

// packsRGB packs a color in the linear color space into its 8-bit sRGB equivalent.
uint packsRGB(vec4 rgba) {
uint packsRGB(mediump vec4 rgba) {
rgba = vec4(tosRGB(rgba.rgb), rgba.a);
return packUnorm4x8(rgba.wzyx);
}
Expand All @@ -69,14 +69,15 @@ uvec2 chunk_offset(uint i) {
return uvec2(i % CHUNK_X * CHUNK_DX, i / CHUNK_X * CHUNK_DY);
}

vec4[CHUNK] fillImage(uvec2 xy, CmdImage cmd_img) {
vec4 rgba[CHUNK];
mediump vec4[CHUNK] fillImage(uvec2 xy, CmdImage cmd_img) {
mediump vec4 rgba[CHUNK];
for (uint i = 0; i < CHUNK; i++) {
ivec2 uv = ivec2(xy + chunk_offset(i)) + cmd_img.offset;
mediump vec4 fg_rgba;
#ifdef ENABLE_IMAGE_INDICES
vec4 fg_rgba = imageLoad(images[cmd_img.index], uv);
fg_rgba = imageLoad(images[cmd_img.index], uv);
#else
vec4 fg_rgba = imageLoad(images[0], uv);
fg_rgba = imageLoad(images[0], uv);
#endif
fg_rgba.rgb = fromsRGB(fg_rgba.rgb);
rgba[i] = fg_rgba;
Expand All @@ -95,7 +96,7 @@ void main() {

uvec2 xy_uint = uvec2(gl_LocalInvocationID.x + TILE_WIDTH_PX * gl_WorkGroupID.x, gl_LocalInvocationID.y + TILE_HEIGHT_PX * gl_WorkGroupID.y);
vec2 xy = vec2(xy_uint);
vec4 rgba[CHUNK];
mediump vec4 rgba[CHUNK];
for (uint i = 0; i < CHUNK; i++) {
rgba[i] = vec4(0.0);
// TODO: remove this debug image support when the actual image method is plumbed.
Expand All @@ -112,7 +113,7 @@ void main() {
#endif
}

float area[CHUNK];
mediump float area[CHUNK];
uint clip_depth = 0;
bool mem_ok = mem_error == NO_ERROR;
while (mem_ok) {
Expand All @@ -124,7 +125,7 @@ void main() {
case Cmd_Stroke:
// Calculate distance field from all the line segments in this tile.
CmdStroke stroke = Cmd_Stroke_read(cmd_alloc, cmd_ref);
float df[CHUNK];
mediump float df[CHUNK];
for (uint k = 0; k < CHUNK; k++) df[k] = 1e9;
TileSegRef tile_seg_ref = TileSegRef(stroke.tile_ref);
do {
Expand Down Expand Up @@ -190,18 +191,18 @@ void main() {
break;
case Cmd_Color:
CmdColor color = Cmd_Color_read(cmd_alloc, cmd_ref);
vec4 fg = unpacksRGB(color.rgba_color);
mediump vec4 fg = unpacksRGB(color.rgba_color);
for (uint k = 0; k < CHUNK; k++) {
vec4 fg_k = fg * area[k];
mediump vec4 fg_k = fg * area[k];
rgba[k] = rgba[k] * (1.0 - fg_k.a) + fg_k;
}
cmd_ref.offset += 4 + CmdColor_size;
break;
case Cmd_Image:
CmdImage fill_img = Cmd_Image_read(cmd_alloc, cmd_ref);
vec4 img[CHUNK] = fillImage(xy_uint, fill_img);
mediump vec4 img[CHUNK] = fillImage(xy_uint, fill_img);
for (uint k = 0; k < CHUNK; k++) {
vec4 fg_k = img[k] * area[k];
mediump vec4 fg_k = img[k] * area[k];
rgba[k] = rgba[k] * (1.0 - fg_k.a) + fg_k;
}
cmd_ref.offset += 4 + CmdImage_size;
Expand All @@ -212,7 +213,7 @@ void main() {
for (uint k = 0; k < CHUNK; k++) {
uvec2 offset = chunk_offset(k);
uint srgb = packsRGB(vec4(rgba[k]));
float alpha = clamp(abs(area[k]), 0.0, 1.0);
mediump float alpha = clamp(abs(area[k]), 0.0, 1.0);
write_mem(scratch_alloc, base_ix + 0 + CLIP_STATE_SIZE * (offset.x + offset.y * TILE_WIDTH_PX), srgb);
write_mem(scratch_alloc, base_ix + 1 + CLIP_STATE_SIZE * (offset.x + offset.y * TILE_WIDTH_PX), floatBitsToUint(alpha));
rgba[k] = vec4(0.0);
Expand All @@ -228,8 +229,8 @@ void main() {
uvec2 offset = chunk_offset(k);
uint srgb = read_mem(scratch_alloc, base_ix + 0 + CLIP_STATE_SIZE * (offset.x + offset.y * TILE_WIDTH_PX));
uint alpha = read_mem(scratch_alloc, base_ix + 1 + CLIP_STATE_SIZE * (offset.x + offset.y * TILE_WIDTH_PX));
vec4 bg = unpacksRGB(srgb);
vec4 fg = rgba[k] * area[k] * uintBitsToFloat(alpha);
mediump vec4 bg = unpacksRGB(srgb);
mediump vec4 fg = rgba[k] * area[k] * uintBitsToFloat(alpha);
rgba[k] = bg * (1.0 - fg.a) + fg;
}
cmd_ref.offset += 4;
Expand Down
Binary file modified piet-gpu/shader/kernel4.spv
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Binary file modified piet-gpu/shader/kernel4_idx.spv
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