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Texture-based thick lines: Allow interpolation between textures for non-integer line widths
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imgui.h
2
imgui.h
@ -2323,7 +2323,7 @@ struct ImFontAtlas
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// [Internal] Packing data
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int PackIdMouseCursors; // Custom texture rectangle ID for white pixel and mouse cursors
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ImVector<int> AALineRectIds; // Custom texture rectangle IDs for anti-aliased lines
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int AALineRectId; // Custom texture rectangle ID for anti-aliased lines
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ImVector<ImVec4> TexUvAALines; // UVs for anti-aliased line textures
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#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
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@ -677,11 +677,12 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
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const float AA_SIZE = 1.0f;
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const ImU32 col_trans = col & ~IM_COL32_A_MASK;
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// The -0.5f here is to better match the geometry-based code, and also shift the transition point from one width texture to another off the integer values (where it will be less noticeable)
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const int integer_thickness = ImMax((int)(thickness - 0.5f), 1);
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// The thick_line test is an attempt to compensate for the way half_draw_size gets calculated later, which special-cases 1.0f width lines
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const int integer_thickness = thick_line ? ImMax((int)(thickness), 1) : 2;
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const float fractional_thickness = thick_line ? (thickness) - integer_thickness : 0.0f;
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// Do we want to draw this line using a texture?
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const bool use_texture = (Flags & ImDrawListFlags_AntiAliasedLinesUseTexData) && (integer_thickness <= IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX);
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const bool use_texture = (Flags & ImDrawListFlags_AntiAliasedLinesUseTexData) && (integer_thickness < IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX);
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// We should never hit this, because NewFrame() doesn't set ImDrawListFlags_AntiAliasedLinesUseTexData unless ImFontAtlasFlags_NoAALines is off
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IM_ASSERT_PARANOID((!use_texture) || (!(_Data->Font->ContainerAtlas->Flags & ImFontAtlasFlags_NoAALines)));
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@ -711,8 +712,9 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
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// If we are drawing a one-pixel-wide line without a texture, or a textured line of any width, we only need 2 or 3 vertices per point
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if (!thick_line || use_texture)
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{
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// The width of the geometry we need to draw
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const float half_draw_size = (!thick_line) ? AA_SIZE : (AA_SIZE + (thickness * 0.5f));
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// The width of the geometry we need to draw - this is essentially <thickness> pixels for the line itself, plus one pixel for AA
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// We don't use AA_SIZE here because the +1 is tied to the generated texture and so alternate values won't work without changes to that code
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const float half_draw_size = (thickness * 0.5f) + 1;
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// If line is not closed, the first and last points need to be generated differently as there are no normals to blend
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if (!closed)
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@ -770,7 +772,18 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
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if (use_texture)
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{
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// If we're using textures we only need to emit the left/right edge vertices
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const ImVec4 tex_uvs = (*_Data->TexUvAALines)[integer_thickness - 1];
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ImVec4 tex_uvs;
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if (fractional_thickness == 0.0f) // Fast path for pure integer widths
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tex_uvs = (*_Data->TexUvAALines)[integer_thickness];
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else
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{
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// Calculate UV by interpolating between the two nearest integer line widths
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const ImVec4 tex_uvs_0 = (*_Data->TexUvAALines)[integer_thickness];
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const ImVec4 tex_uvs_1 = (*_Data->TexUvAALines)[integer_thickness + 1];
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tex_uvs = ImLerp(tex_uvs_0, tex_uvs_1, fractional_thickness);
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}
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for (int i = 0; i < points_count; i++)
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{
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@ -2373,24 +2386,14 @@ static void ImFontAtlasBuildRenderDefaultTexData(ImFontAtlas* atlas)
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atlas->TexUvWhitePixel = ImVec2((r->X + 0.5f) * atlas->TexUvScale.x, (r->Y + 0.5f) * atlas->TexUvScale.y);
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}
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// This is called/shared by both the stb_truetype and the FreeType builder.
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const unsigned int FONT_ATLAS_AA_LINE_TEX_HEIGHT = 1; // Technically we only need 1 pixel in the ideal case but this can be increased if necessary to give a border to avoid sampling artifacts
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static void ImFontAtlasBuildRegisterAALineCustomRects(ImFontAtlas* atlas)
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{
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if (atlas->AALineRectIds.Size > 0)
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return;
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if ((atlas->Flags & ImFontAtlasFlags_NoAALines))
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return;
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for (int n = 0; n < IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX; n++)
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{
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// The "width + 3" here is interesting. +2 is to give space for the end caps, but the remaining +1 is
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// because (empirically) to match the behavior of the untextured render path we need to draw lines one pixel wider.
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const int width = n + 1; // The line width this entry corresponds to
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atlas->AALineRectIds.push_back(atlas->AddCustomRectRegular(width + 3, FONT_ATLAS_AA_LINE_TEX_HEIGHT));
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}
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const int max_width = IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX; // The maximum line width we want to generate
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// The "max_width + 2" here is to give space for the end caps, whilst height (IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX+1) is to accommodate the fact we have a zero-width row
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atlas->AALineRectId = atlas->AddCustomRectRegular(max_width + 2, IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX + 1);
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}
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static void ImFontAtlasBuildRenderAALinesTexData(ImFontAtlas* atlas)
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@ -2401,27 +2404,42 @@ static void ImFontAtlasBuildRenderAALinesTexData(ImFontAtlas* atlas)
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if (atlas->Flags & ImFontAtlasFlags_NoAALines)
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return;
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const int w = atlas->TexWidth;
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for (unsigned int n = 0; n < IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX; n++)
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{
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IM_ASSERT(atlas->AALineRectIds.Size > (int)n);
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ImFontAtlasCustomRect& r = atlas->CustomRects[atlas->AALineRectIds[n]];
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IM_ASSERT(r.IsPacked());
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ImFontAtlasCustomRect& r = atlas->CustomRects[atlas->AALineRectId];
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IM_ASSERT(r.IsPacked());
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// We fill as many lines as we were given, to allow for >1 lines being used to work around sampling weirdness
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for (unsigned int y = 0; y < r.Height; y++)
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{
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// Each line consists of two empty pixels at the ends, with a line of solid pixels in the middle
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unsigned char* write_ptr = &atlas->TexPixelsAlpha8[r.X + ((r.Y + y) * w)];
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// This generates a triangular shape in the texture, with the various line widths stacked on top of each other to allow interpolation between them
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const int w = atlas->TexWidth;
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for (unsigned int n = 0; n < (IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX + 1); n++) // +1 because of the zero-width row
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{
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unsigned int y = n;
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unsigned int line_width = n;
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// Each line consists of at least two empty pixels at the ends, with a line of solid pixels in the middle
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unsigned int pad_left = (r.Width - line_width) / 2;
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unsigned int pad_right = r.Width - (pad_left + line_width);
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// Make sure we're inside the texture bounds before we start writing pixels
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IM_ASSERT_PARANOID(pad_left + line_width + pad_right == r.Width);
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IM_ASSERT_PARANOID(y < r.Height);
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// Write each slice
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unsigned char* write_ptr = &atlas->TexPixelsAlpha8[r.X + ((r.Y + y) * w)];
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for (unsigned int x = 0; x < pad_left; x++)
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*(write_ptr++) = 0;
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for (unsigned short x = 0; x < (r.Width - 2U); x++)
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*(write_ptr++) = 0xFF;
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for (unsigned int x = 0; x < line_width; x++)
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*(write_ptr++) = 0xFF;
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for (unsigned int x = 0; x < pad_right; x++)
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*(write_ptr++) = 0;
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}
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// Calculate UVs for this line
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ImFontAtlasCustomRect line_rect = r;
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line_rect.X += (unsigned short)(pad_left - 1);
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line_rect.Width = (unsigned short)(line_width + 2);
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line_rect.Y += (unsigned short)y;
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line_rect.Height = 1;
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ImVec2 uv0, uv1;
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atlas->CalcCustomRectUV(&r, &uv0, &uv1);
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float halfV = (uv0.y + uv1.y) * 0.5f; // Calculate a constant V in the middle of the texture as we want a horizontal slice (with some padding either side to avoid sampling artifacts)
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atlas->CalcCustomRectUV(&line_rect, &uv0, &uv1);
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float halfV = (uv0.y + uv1.y) * 0.5f; // Calculate a constant V in the middle of the row to avoid sampling artifacts
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atlas->TexUvAALines.push_back(ImVec4(uv0.x, halfV, uv1.x, halfV));
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}
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}
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@ -529,7 +529,7 @@ struct IMGUI_API ImChunkStream
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#define IM_DRAWLIST_ARCFAST_TESSELLATION_MULTIPLIER 1
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#endif
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// The maximum line width to build anti-aliased textures for
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// The maximum line width to build anti-aliased textures for (note that this needs to be one greater than the maximum line width you want to be able to draw using the textured path)
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#define IM_DRAWLIST_TEX_AA_LINES_WIDTH_MAX 65
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// Data shared between all ImDrawList instances
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