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https://github.com/italicsjenga/vello.git
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8fab45544e
Expand the the final kernel4 stage to maintain a per-pixel mask. Introduce two new path elements, FillMask and FillMaskInv, to fill the mask. FillMask acts like Fill, while FillMaskInv fills the area outside the path. SVG clipPaths is then representable by a FillMaskInv(0.0) for every nested path, preceded by a FillMask(1.0) to clear the mask. The bounding box for FillMaskInv elements is the entire screen; tightening of the bounding box is left for future work. Note that a fullscreen bounding box is not hopelessly inefficient because completely filling a tile with a mask is just a single CmdSolidMask per tile. Fixes #30 Signed-off-by: Elias Naur <mail@eliasnaur.com>
108 lines
3.6 KiB
Plaintext
108 lines
3.6 KiB
Plaintext
// Propagation of tile backdrop for filling.
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//
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// Each thread reads one path element and calculates the number of spanned tiles
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// based on the bounding box.
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// In a further compaction step, the workgroup loops over the corresponding tile rows per element in parallel.
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// For each row the per tile backdrop will be read, as calculated in the previous coarse path segment kernel,
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// and propagated from the left to the right (prefix summed).
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//
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// Output state:
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// - Each path element has an array of tiles covering the whole path based on boundig box
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// - Each tile per path element contains the 'backdrop' and a list of subdivided path segments
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#version 450
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#extension GL_GOOGLE_include_directive : enable
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#include "setup.h"
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#define LG_BACKDROP_WG (7 + LG_WG_FACTOR)
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#define BACKDROP_WG (1 << LG_BACKDROP_WG)
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layout(local_size_x = BACKDROP_WG, local_size_y = 1) in;
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layout(set = 0, binding = 0) buffer AnnotatedBuf {
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uint[] annotated;
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};
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// This is really only used for n_elements; maybe we can handle that
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// a different way, but it's convenient to have the same signature as
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// tile allocation.
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layout(set = 0, binding = 1) readonly buffer AllocBuf {
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uint n_elements; // paths
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uint n_pathseg;
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uint alloc;
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};
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layout(set = 0, binding = 2) buffer TileBuf {
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uint[] tile;
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};
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#include "annotated.h"
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#include "tile.h"
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shared uint sh_row_count[BACKDROP_WG];
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shared uint sh_row_base[BACKDROP_WG];
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shared uint sh_row_width[BACKDROP_WG];
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void main() {
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uint th_ix = gl_LocalInvocationID.x;
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uint element_ix = gl_GlobalInvocationID.x;
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AnnotatedRef ref = AnnotatedRef(element_ix * Annotated_size);
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// Work assignment: 1 thread : 1 path element
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uint row_count = 0;
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if (element_ix < n_elements) {
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uint tag = Annotated_tag(ref);
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switch (tag) {
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case Annotated_Fill:
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case Annotated_FillMask:
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case Annotated_FillMaskInv:
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PathRef path_ref = PathRef(element_ix * Path_size);
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Path path = Path_read(path_ref);
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sh_row_width[th_ix] = path.bbox.z - path.bbox.x;
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row_count = path.bbox.w - path.bbox.y;
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if (row_count == 1) {
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// Note: this can probably be expanded to width = 2 as
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// long as it doesn't cross the left edge.
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row_count = 0;
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}
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sh_row_base[th_ix] = (path.tiles.offset >> 2) + 1;
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}
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}
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sh_row_count[th_ix] = row_count;
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// Prefix sum of sh_row_count
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for (uint i = 0; i < LG_BACKDROP_WG; i++) {
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barrier();
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if (th_ix >= (1 << i)) {
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row_count += sh_row_count[th_ix - (1 << i)];
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}
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barrier();
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sh_row_count[th_ix] = row_count;
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}
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barrier();
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// Work assignment: 1 thread : 1 path element row
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uint total_rows = sh_row_count[BACKDROP_WG - 1];
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for (uint row = th_ix; row < total_rows; row += BACKDROP_WG) {
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// Binary search to find element
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uint el_ix = 0;
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for (uint i = 0; i < LG_BACKDROP_WG; i++) {
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uint probe = el_ix + ((BACKDROP_WG / 2) >> i);
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if (row >= sh_row_count[probe - 1]) {
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el_ix = probe;
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}
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}
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uint seq_ix = row - (el_ix > 0 ? sh_row_count[el_ix - 1] : 0);
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uint width = sh_row_width[el_ix];
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// Process one row sequentially
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// Read backdrop value per tile and prefix sum it
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uint tile_el_ix = sh_row_base[el_ix] + seq_ix * 2 * width;
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uint sum = tile[tile_el_ix];
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for (uint x = 1; x < width; x++) {
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tile_el_ix += 2;
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sum += tile[tile_el_ix];
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tile[tile_el_ix] = sum;
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}
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}
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}
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