mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-27 02:32:02 -04:00
Matthew Stanley
928085d5fb
Adapt PR #14's biased 32.32 triangle edge DDA and half-open bottom/right coverage across the software raster paths, with a focused pure edge-math regression test. Source: https://github.com/mstan/psxrecomp/pull/14 Source-commit: https://github.com/mstan/psxrecomp/commit/91a654f61dff18806f3eea43f72a30cb34430695 Co-authored-by: Kareem Olim <kareemolim@gmail.com>
40 lines
1.4 KiB
C
40 lines
1.4 KiB
C
#ifndef PSXRECOMP_GPU_SW_EDGES_H
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#define PSXRECOMP_GPU_SW_EDGES_H
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#include <stdint.h>
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/* PS1 polygon coverage uses a biased 32.32 edge DDA with exclusive bottom
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* and right edges. Float-truncated inclusive spans make adjacent polygons
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* disagree by a pixel and draw a shared diagonal twice. */
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static inline int64_t psx_edge_fp(int x) {
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return ((int64_t)x << 32) + ((1LL << 32) - (1 << 11));
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}
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static inline int64_t psx_edge_step(int dx, int dy) {
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int64_t rounding = dx < 0 ? -(int64_t)(dy - 1)
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: (dx > 0 ? (int64_t)(dy - 1) : 0);
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return (((int64_t)dx << 32) + rounding) / dy;
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}
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static inline int psx_edge_unfp(int64_t fp) {
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return (int)((uint64_t)fp >> 32);
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}
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/* Vertices must already be sorted by Y. y is in [y0,y2). */
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static inline void psx_triangle_edges_at_y(int x0, int y0, int x1, int y1,
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int x2, int y2, int y,
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int *long_x, int *short_x) {
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int64_t long_step = psx_edge_step(x2 - x0, y2 - y0);
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*long_x = psx_edge_unfp(psx_edge_fp(x0) + long_step * (y - y0));
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if (y < y1) {
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int64_t short_step = psx_edge_step(x1 - x0, y1 - y0);
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*short_x = psx_edge_unfp(psx_edge_fp(x0) + short_step * (y - y0));
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} else {
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int64_t short_step = psx_edge_step(x2 - x1, y2 - y1);
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*short_x = psx_edge_unfp(psx_edge_fp(x1) + short_step * (y - y1));
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}
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}
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#endif
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