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DrawList: fixed visual pop in stroke rendering when thickness is between 1 and 2 pixels.

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- added animated thickness to demo to make it easier to evaluate thickness visual progression
- added super sampled textures in thickness range [1..3] to avoid visual pop
This commit is contained in:
Mikko Mononen
2026-05-26 15:52:59 +03:00
committed by ocornut
parent ac89e342e7
commit e30d8e7888
3 changed files with 142 additions and 50 deletions
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165
imgui_draw.cpp
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@@ -1187,6 +1187,27 @@ static ImU32 ImAlphaMultiply(ImU32 col, float alpha_mul)
return (col & ~IM_COL32_A_MASK) | (a << IM_COL32_A_SHIFT);
}
void ImDrawList::_SelectFringeTexture(float screen_thickness, ImVec4& tex_uvs, float& fringe)
{
if (screen_thickness <= 2.f)
{
// Handle the thickness between [1..2]. The texture scaling in this range will cause visual pop near 1, so we generate super sampled textures in this range.
// There IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX+1 textures, where 0 maps to 1.0 and IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX maps 2.0.
constexpr float base_width = 1.f;
const int texture_idx = ImClamp((int)((screen_thickness - base_width) * IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX + 0.5f), 0, IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX);
const float tex_width = base_width + (float)texture_idx / IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX;
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];
}
else
{
// Bias the texture selection towards higher resolution to avoid visual pops when the texture change.
const int texture_idx = ImClamp((int)(screen_thickness + 0.95f), 1, IM_DRAWLIST_TEX_LINES_WIDTH_MAX - 1);
fringe = _FringeScale * (screen_thickness / (float)texture_idx); // Scale the fringe to cover the discrepancy between the texture and requested size.
tex_uvs = _Data->TexUvLines[texture_idx];
}
}
extern bool g_LEGACY_STROKES;
void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32 col, float thickness, ImDrawFlags flags)
@@ -1244,10 +1265,9 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
sqr_lengths[points_count - 1] = 0.0f;
}
// Bias the texture selection towards higher resolution to avoid visual pops when the texture change.
const int texture_idx = ImClamp((int)(screen_thickness + 0.95f), 1, IM_DRAWLIST_TEX_LINES_WIDTH_MAX - 1);
const float fringe = _FringeScale * (screen_thickness / (float)texture_idx); // Scale the fringe to cover the discrepancy between the texture and requested size.
const ImVec4 tex_uvs = _Data->TexUvLines[texture_idx];
ImVec4 tex_uvs;
float fringe;
_SelectFringeTexture(screen_thickness, tex_uvs, fringe);
_AddPolyline(points, normals, sqr_lengths, points_count, col, thickness, flags, tex_uvs, fringe);
}
@@ -2352,10 +2372,9 @@ void ImDrawList::_AddRectTinyRounding(const ImVec2& p_min, const ImVec2& p_max,
thickness = _FringeScale;
}
// Bias the texture selection towards higher resolution to avoid visual pops when the texture change.
const int texture_idx = ImClamp((int)(screen_thickness + 0.95f), 1, IM_DRAWLIST_TEX_LINES_WIDTH_MAX - 1);
const float fringe = _FringeScale * (screen_thickness / (float)texture_idx); // Scale the fringe to cover the discrepancy between the texture and requested size.
const ImVec4 tex_uvs = _Data->TexUvLines[texture_idx];
ImVec4 tex_uvs;
float fringe;
_SelectFringeTexture(screen_thickness, tex_uvs, fringe);
const int arc_step = ImClamp(IM_DRAWLIST_ARCFAST_SAMPLE_MAX / this->_CalcCircleAutoSegmentCount(rounding), 1, IM_DRAWLIST_ARCFAST_TABLE_SIZE / 4);
const int arc_point_count = (IM_DRAWLIST_ARCFAST_TABLE_SIZE / 4) / arc_step + 1;
@@ -5101,54 +5120,114 @@ static void ImFontAtlasBuildUpdateTexDataLines(ImFontAtlas* atlas)
bool add_and_draw = atlas->GetCustomRect(builder->PackIdLinesTexData, &r) == false;
if (add_and_draw)
{
ImVec2i pack_size = ImVec2i(IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 2, IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1);
ImVec2i pack_size = ImVec2i(IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 2, IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1 + IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX + 1);
builder->PackIdLinesTexData = atlas->AddCustomRect(pack_size.x, pack_size.y, &r);
IM_ASSERT(builder->PackIdLinesTexData != ImFontAtlasRectId_Invalid);
}
// Register texture region for thick lines
// The +2 here is to give space for the end caps, whilst height +1 is to accommodate the fact we have a zero-width row
// This generates a triangular shape in the texture, with the various line widths stacked on top of each other to allow interpolation between them
for (int n = 0; n < IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1; n++) // +1 because of the zero-width row
{
// Each line consists of at least two empty pixels at the ends, with a line of solid pixels in the middle
const int y = n;
const int line_width = n;
const int pad_left = (r.w - line_width) / 2;
const int pad_right = r.w - (pad_left + line_width);
IM_ASSERT(pad_left + line_width + pad_right == r.w && y < r.h); // Make sure we're inside the texture bounds before we start writing pixels
// Write each slice
if (add_and_draw && tex->Format == ImTextureFormat_Alpha8)
// Register texture region for thick lines
// The +2 here is to give space for the end caps, whilst height +1 is to accommodate the fact we have a zero-width row
// This generates a triangular shape in the texture, with the various line widths stacked on top of each other to allow interpolation between them
for (int n = 0; n < IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1; n++) // +1 because of the zero-width row
{
ImU8* write_ptr = (ImU8*)tex->GetPixelsAt(r.x, r.y + y);
for (int i = 0; i < pad_left; i++)
*(write_ptr + i) = 0x00;
// Each line consists of at least two empty pixels at the ends, with a line of solid pixels in the middle
const int y = n;
const int line_width = n;
const int pad_left = (r.w - line_width) / 2;
const int pad_right = r.w - (pad_left + line_width);
IM_ASSERT(pad_left + line_width + pad_right == r.w && y < r.h); // Make sure we're inside the texture bounds before we start writing pixels
for (int i = 0; i < line_width; i++)
*(write_ptr + pad_left + i) = 0xFF;
// Write each slice
if (add_and_draw && tex->Format == ImTextureFormat_Alpha8)
{
ImU8* write_ptr = (ImU8*)tex->GetPixelsAt(r.x, r.y + y);
for (int i = 0; i < pad_left; i++)
*(write_ptr + i) = 0x00;
for (int i = 0; i < pad_right; i++)
*(write_ptr + pad_left + line_width + i) = 0x00;
for (int i = 0; i < line_width; i++)
*(write_ptr + pad_left + i) = 0xFF;
for (int i = 0; i < pad_right; i++)
*(write_ptr + pad_left + line_width + i) = 0x00;
}
else if (add_and_draw && tex->Format == ImTextureFormat_RGBA32)
{
ImU32* write_ptr = (ImU32*)(void*)tex->GetPixelsAt(r.x, r.y + y);
for (int i = 0; i < pad_left; i++)
*(write_ptr + i) = IM_COL32(255, 255, 255, 0);
for (int i = 0; i < line_width; i++)
*(write_ptr + pad_left + i) = IM_COL32_WHITE;
for (int i = 0; i < pad_right; i++)
*(write_ptr + pad_left + line_width + i) = IM_COL32(255, 255, 255, 0);
}
// Refresh UV coordinates
ImVec2 uv0 = ImVec2((float)(r.x + pad_left - 1), (float)(r.y + y)) * atlas->TexUvScale;
ImVec2 uv1 = ImVec2((float)(r.x + pad_left + line_width + 1), (float)(r.y + y + 1)) * atlas->TexUvScale;
float half_v = (uv0.y + uv1.y) * 0.5f; // Calculate a constant V in the middle of the row to avoid sampling artifacts
atlas->TexUvLines[n] = ImVec4(uv0.x, half_v, uv1.x, half_v);
}
else if (add_and_draw && tex->Format == ImTextureFormat_RGBA32)
}
{
ImU8 ramp[IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX];
for (int n = 0; n < IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX; n++)
ramp[n] = (ImU8)(((float)n / IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX) * 255.f);
for (int n = 0; n < IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX + 1; n++)
{
ImU32* write_ptr = (ImU32*)(void*)tex->GetPixelsAt(r.x, r.y + y);
for (int i = 0; i < pad_left; i++)
*(write_ptr + i) = IM_COL32(255, 255, 255, 0);
// 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_SUPERSAMPLE_MAX + n;
IM_ASSERT(IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX + line_width + IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX <= r.w && y < r.h); // Make sure we're inside the texture bounds before we start writing pixels
for (int i = 0; i < line_width; i++)
*(write_ptr + pad_left + i) = IM_COL32_WHITE;
// Write each slice
if (add_and_draw && tex->Format == ImTextureFormat_Alpha8)
{
ImU8* write_ptr = (ImU8*)tex->GetPixelsAt(r.x, r.y + y);
int idx = 0;
for (int i = 0; i < pad_right; i++)
*(write_ptr + pad_left + line_width + i) = IM_COL32(255, 255, 255, 0);
for (int i = 0; i < IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX; i++)
write_ptr[idx++] = ramp[i];
for (int i = 0; i < line_width; i++)
write_ptr[idx++] = 0xFF;
for (int i = IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX-1; i >= 0; i--)
write_ptr[idx++] = ramp[i];
while (idx < r.w)
write_ptr[idx++] = 0x0;
}
else if (add_and_draw && tex->Format == ImTextureFormat_RGBA32)
{
ImU32* write_ptr = (ImU32*)(void*)tex->GetPixelsAt(r.x, r.y + y);
int idx = 0;
for (int i = 0; i < IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX; i++)
write_ptr[idx++] = IM_COL32(255, 255, 255, ramp[i]);
for (int i = 0; i < line_width; i++)
write_ptr[idx++] = IM_COL32(255, 255, 255, 255);
for (int i = IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX - 1; i >= 0; i--)
write_ptr[idx++] = IM_COL32(255, 255, 255, ramp[i]);
while (idx < r.w)
write_ptr[idx++] = IM_COL32(255, 255, 255, 0);
}
// Refresh UV coordinates
ImVec2 uv0 = ImVec2((float)(r.x), (float)(r.y + y)) * atlas->TexUvScale;
ImVec2 uv1 = ImVec2((float)(r.x + IM_DRAWLIST_TEX_LINES_SUPERSAMPLE_MAX * 2 + line_width), (float)(r.y + y + 1)) * atlas->TexUvScale;
float half_v = (uv0.y + uv1.y) * 0.5f; // Calculate a constant V in the middle of the row to avoid sampling artifacts
atlas->TexUvLines[IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1 + n] = ImVec4(uv0.x, half_v, uv1.x, half_v);
}
// Refresh UV coordinates
ImVec2 uv0 = ImVec2((float)(r.x + pad_left - 1), (float)(r.y + y)) * atlas->TexUvScale;
ImVec2 uv1 = ImVec2((float)(r.x + pad_left + line_width + 1), (float)(r.y + y + 1)) * atlas->TexUvScale;
float half_v = (uv0.y + uv1.y) * 0.5f; // Calculate a constant V in the middle of the row to avoid sampling artifacts
atlas->TexUvLines[n] = ImVec4(uv0.x, half_v, uv1.x, half_v);
}
}