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DrawList: fixed thin lines appearing too bright.

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- fixed how super sampled line textures are generated (and documented wrong assumption)
- switched to more samples and smaller thickness range
- tweaked super sampled texture selection to hide the texture changed better
This commit is contained in:
Mikko Mononen
2026-05-26 22:10:25 +03:00
committed by ocornut
parent 1f61cad3d6
commit 51da1f5de6
2 changed files with 16 additions and 7 deletions
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19
imgui_draw.cpp
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@@ -1189,15 +1189,15 @@ static ImU32 ImAlphaMultiply(ImU32 col, float alpha_mul)
void ImDrawList::_SelectFringeTexture(float screen_thickness, ImVec4& tex_uvs, float& fringe)
{
if (screen_thickness <= 2.f)
if (screen_thickness <= IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH)
{
// Handle the thickness between [1..IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH]. The texture scaling in this range will cause slight visual pops, so we generate super sampled textures in this range.
// There are IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH_MAX+1 textures, where 0 maps to 1.0 and IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH_MAX maps to IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH.
constexpr float base_width = 1.f;
const int texture_idx = ImClamp((int)((screen_thickness - base_width) * IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT + 0.995f), 0, IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH_MAX);
const int texture_idx = ImClamp((int)((screen_thickness - base_width) * IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT + 0.1f), 0, IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH_MAX);
const float tex_width = base_width + (float)texture_idx / IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT;
fringe = _FringeScale * (screen_thickness / tex_width); // Scale the fringe to cover the discrepancy between the texture and requested size.
tex_uvs = _Data->TexUvLines[IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1 + texture_idx];
tex_uvs = _Data->TexUvLines[(IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1) + texture_idx];
}
else
{
@@ -5182,9 +5182,18 @@ static void ImFontAtlasBuildUpdateTexDataLines(ImFontAtlas* atlas)
for (int n = 0; n < IM_DRAWLIST_TEX_LINES_DETAILED_WIDTH_MAX + 1; n++)
{
// Each line consists of at least two empty pixels at the ends, with a line of solid pixels in the middle
const int y = IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1 + n;
const int line_width = IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT + n;
// For integer thickness lines the one pixel line texture looks like this:
// [ 0 | 1 | 0 ]
// :...........:
// Since the texture samples are at the center of the texel, we only use range above.
// The result after bilinear filtering is a triangle across the used uv range.
//
// To super 2x sample that signal, we end up with following texture:
// [ 0 | .5 | 1 | .5 | 0 ]
// :.......................:
// One might think that there should be 2 opaque pixels the the middle section, but no singe we're super sampling the triangle signal.
const int line_width = 1 + n;
IM_ASSERT(IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT + line_width + IM_DRAWLIST_TEX_LINES_SAMPLE_COUNT <= r.w && y < r.h); // Make sure we're inside the texture bounds before we start writing pixels
// Write each slice