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Texture-based thick lines: Initial version of AA line drawing using textures (press SHIFT to enable)

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This commit is contained in:
Ben Carter
2020-01-13 14:24:55 +09:00
committed by omar
parent 8e4046e13b
commit 1d3c3070d8
5 changed files with 206 additions and 27 deletions
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156
imgui_draw.cpp
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@ -667,6 +667,7 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
const ImVec2 opaque_uv = _Data->TexUvWhitePixel;
const int count = closed ? points_count : points_count - 1; // The number of line segments we need to draw
const bool thick_line = (thickness > 1.0f);
if (Flags & ImDrawListFlags_AntiAliasedLines)
@ -675,13 +676,24 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
const float AA_SIZE = 1.0f;
const ImU32 col_trans = col & ~IM_COL32_A_MASK;
const int idx_count = thick_line ? count * 18 : count * 12;
const int vtx_count = thick_line ? points_count * 4 : points_count * 3;
const int integer_thickness = (int)thickness;
// Do we want to draw this line using a texture?
bool use_textures = (Flags & ImDrawListFlags_TexturedAALines) &&
(integer_thickness >= 1) &&
(integer_thickness <= _Data->Font->ContainerAtlas->AALineMaxWidth) &&
ImGui::GetIO().KeyShift; // FIXME-AALINES: Remove this debug code
// We should never hit this, because NewFrame() doesn't set ImDrawListFlags_TexturedAALines unless ImFontAtlasFlags_NoAALines is off
IM_ASSERT_PARANOID((!use_textures) || (!(_Data->Font->ContainerAtlas->Flags & ImFontAtlasFlags_NoAALines)));
const int idx_count = use_textures ? (count * 6) : (thick_line ? count * 18 : count * 12);
const int vtx_count = use_textures ? (points_count * 2) : (thick_line ? points_count * 4 : points_count * 3);
PrimReserve(idx_count, vtx_count);
// Temporary buffer
// The first <points_count> items are normals at each line point, then after that there are either 2 or 4 temp points for each line point
ImVec2* temp_normals = (ImVec2*)alloca(points_count * (thick_line ? 5 : 3) * sizeof(ImVec2)); //-V630
ImVec2* temp_normals = (ImVec2*)alloca(points_count * ((thick_line && !use_textures) ? 5 : 3) * sizeof(ImVec2)); //-V630
ImVec2* temp_points = temp_normals + points_count;
// Calculate normals (tangents) for each line segment
@ -697,14 +709,19 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
if (!closed)
temp_normals[points_count - 1] = temp_normals[points_count - 2];
if (!thick_line)
// 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
if ((!thick_line) || (use_textures))
{
// The width of the geometry we need to draw
const float half_draw_size = (!thick_line) ? AA_SIZE : (AA_SIZE + (thickness * 0.5f));
// If line is not closed, the first and last points need to be generated differently as there are no normals to blend
if (!closed)
{
temp_points[0] = points[0] + temp_normals[0] * AA_SIZE;
temp_points[1] = points[0] - temp_normals[0] * AA_SIZE;
temp_points[(points_count-1)*2+0] = points[points_count-1] + temp_normals[points_count-1] * AA_SIZE;
temp_points[(points_count-1)*2+1] = points[points_count-1] - temp_normals[points_count-1] * AA_SIZE;
temp_points[0] = points[0] + temp_normals[0] * half_draw_size;
temp_points[1] = points[0] - temp_normals[0] * half_draw_size;
temp_points[(points_count-1)*2+0] = points[points_count-1] + temp_normals[points_count-1] * half_draw_size;
temp_points[(points_count-1)*2+1] = points[points_count-1] - temp_normals[points_count-1] * half_draw_size;
}
// Generate the indices to form a number of triangles for each line segment, and the vertices for the line edges
@ -713,15 +730,15 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
unsigned int idx1 = _VtxCurrentIdx; // Vertex index for start of line segment
for (int i1 = 0; i1 < count; i1++) // i1 is the first point of the line segment
{
const int i2 = (i1 + 1) == points_count ? 0 : i1 + 1;
const unsigned int idx2 = (i1 + 1) == points_count ? _VtxCurrentIdx : idx1 + 3;
const int i2 = (i1 + 1) == points_count ? 0 : i1 + 1; // i2 is the second point of the line segment
unsigned int idx2 = ((i1 + 1) == points_count) ? _VtxCurrentIdx : (idx1 + (use_textures ? 2 : 3)); // Vertex index for end of segment
// Average normals
float dm_x = (temp_normals[i1].x + temp_normals[i2].x) * 0.5f;
float dm_y = (temp_normals[i1].y + temp_normals[i2].y) * 0.5f;
IM_FIXNORMAL2F(dm_x, dm_y);
dm_x *= AA_SIZE;
dm_y *= AA_SIZE;
dm_x *= half_draw_size; // dm_x, dm_y are offset to the outer edge of the AA area
dm_y *= half_draw_size;
// Add temporary vertexes for the outer edges
ImVec2* out_vtx = &temp_points[i2 * 2];
@ -730,28 +747,54 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
out_vtx[1].x = points[i2].x - dm_x;
out_vtx[1].y = points[i2].y - dm_y;
// Add indexes for four triangles
_IdxWritePtr[0] = (ImDrawIdx)(idx2+0); _IdxWritePtr[1] = (ImDrawIdx)(idx1+0); _IdxWritePtr[2] = (ImDrawIdx)(idx1+2);
_IdxWritePtr[3] = (ImDrawIdx)(idx1+2); _IdxWritePtr[4] = (ImDrawIdx)(idx2+2); _IdxWritePtr[5] = (ImDrawIdx)(idx2+0);
_IdxWritePtr[6] = (ImDrawIdx)(idx2+1); _IdxWritePtr[7] = (ImDrawIdx)(idx1+1); _IdxWritePtr[8] = (ImDrawIdx)(idx1+0);
_IdxWritePtr[9] = (ImDrawIdx)(idx1+0); _IdxWritePtr[10]= (ImDrawIdx)(idx2+0); _IdxWritePtr[11]= (ImDrawIdx)(idx2+1);
_IdxWritePtr += 12;
if (use_textures)
{
// Add indices for two triangles
_IdxWritePtr[0] = (ImDrawIdx)(idx2 + 0); _IdxWritePtr[1] = (ImDrawIdx)(idx1 + 0); _IdxWritePtr[2] = (ImDrawIdx)(idx1 + 1); // Right tri
_IdxWritePtr[3] = (ImDrawIdx)(idx2 + 1); _IdxWritePtr[4] = (ImDrawIdx)(idx1 + 1); _IdxWritePtr[5] = (ImDrawIdx)(idx2 + 0); // Left tri
_IdxWritePtr += 6;
}
else
{
// Add indexes for four triangles
_IdxWritePtr[0] = (ImDrawIdx)(idx2 + 0); _IdxWritePtr[1] = (ImDrawIdx)(idx1 + 0); _IdxWritePtr[2] = (ImDrawIdx)(idx1 + 2); // Right tri 1
_IdxWritePtr[3] = (ImDrawIdx)(idx1 + 2); _IdxWritePtr[4] = (ImDrawIdx)(idx2 + 2); _IdxWritePtr[5] = (ImDrawIdx)(idx2 + 0); // Right tri 2
_IdxWritePtr[6] = (ImDrawIdx)(idx2 + 1); _IdxWritePtr[7] = (ImDrawIdx)(idx1 + 1); _IdxWritePtr[8] = (ImDrawIdx)(idx1 + 0); // Left tri 1
_IdxWritePtr[9] = (ImDrawIdx)(idx1 + 0); _IdxWritePtr[10] = (ImDrawIdx)(idx2 + 0); _IdxWritePtr[11] = (ImDrawIdx)(idx2 + 1); // Left tri 2
_IdxWritePtr += 12;
}
idx1 = idx2;
}
// Add vertexes for each point on the line
for (int i = 0; i < points_count; i++)
if (use_textures)
{
_VtxWritePtr[0].pos = points[i]; _VtxWritePtr[0].uv = opaque_uv; _VtxWritePtr[0].col = col;
_VtxWritePtr[1].pos = temp_points[i*2+0]; _VtxWritePtr[1].uv = opaque_uv; _VtxWritePtr[1].col = col_trans;
_VtxWritePtr[2].pos = temp_points[i*2+1]; _VtxWritePtr[2].uv = opaque_uv; _VtxWritePtr[2].col = col_trans;
_VtxWritePtr += 3;
// If we're using textures we only need to emit the left/right edge vertices
const ImVec4 tex_uvs = (*_Data->TexUvAALines)[integer_thickness - 1];
for (int i = 0; i < points_count; i++)
{
_VtxWritePtr[0].pos = temp_points[i * 2 + 0]; _VtxWritePtr[0].uv = ImVec2(tex_uvs.x, tex_uvs.y); _VtxWritePtr[0].col = col; // Left-side outer edge
_VtxWritePtr[1].pos = temp_points[i * 2 + 1]; _VtxWritePtr[1].uv = ImVec2(tex_uvs.z, tex_uvs.y); _VtxWritePtr[1].col = col; // Right-side outer edge
_VtxWritePtr += 2;
}
}
else
{
// If we're not using a texture, we need the centre vertex as well
for (int i = 0; i < points_count; i++)
{
_VtxWritePtr[0].pos = points[i]; _VtxWritePtr[0].uv = opaque_uv; _VtxWritePtr[0].col = col; // Centre of line
_VtxWritePtr[1].pos = temp_points[i * 2 + 0]; _VtxWritePtr[1].uv = opaque_uv; _VtxWritePtr[1].col = col_trans; // Left-side outer edge
_VtxWritePtr[2].pos = temp_points[i * 2 + 1]; _VtxWritePtr[2].uv = opaque_uv; _VtxWritePtr[2].col = col_trans; // Right-side outer edge
_VtxWritePtr += 3;
}
}
}
else
{
// Non texture-based lines (thick): we need to draw the solid line core and thus require four vertices per point
// For untextured lines that are greater than a pixel in width, we need to draw the solid line core and thus require four vertices per point
const float half_inner_thickness = (thickness - AA_SIZE) * 0.5f;
// If line is not closed, the first and last points need to be generated differently as there are no normals to blend
@ -1664,6 +1707,8 @@ ImFontAtlas::ImFontAtlas()
TexUvScale = ImVec2(0.0f, 0.0f);
TexUvWhitePixel = ImVec2(0.0f, 0.0f);
PackIdMouseCursors = -1;
AALineMaxWidth = 8;
}
ImFontAtlas::~ImFontAtlas()
@ -2010,6 +2055,7 @@ bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
IM_ASSERT(atlas->ConfigData.Size > 0);
ImFontAtlasBuildInit(atlas);
ImFontAtlasBuildRegisterAALineCustomRects(atlas);
// Clear atlas
atlas->TexID = (ImTextureID)NULL;
@ -2331,7 +2377,6 @@ static void ImFontAtlasBuildRenderDefaultTexData(ImFontAtlas* atlas)
atlas->TexUvWhitePixel = ImVec2((r->X + 0.5f) * atlas->TexUvScale.x, (r->Y + 0.5f) * atlas->TexUvScale.y);
}
// Note: this is called / shared by both the stb_truetype and the FreeType builder
void ImFontAtlasBuildInit(ImFontAtlas* atlas)
{
@ -2346,12 +2391,73 @@ void ImFontAtlasBuildInit(ImFontAtlas* atlas)
}
// This is called/shared by both the stb_truetype and the FreeType builder.
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
void ImFontAtlasBuildRegisterAALineCustomRects(ImFontAtlas* atlas)
{
if (atlas->AALineRectIds.size() > 0)
return;
if ((atlas->Flags & ImFontAtlasFlags_NoAALines))
return;
const int max = atlas->AALineMaxWidth;
for (int n = 0; n < max; n++)
{
const int width = n + 1; // The line width this entry corresponds to
// The "width + 3" here is interesting - +2 is to give space for the end caps, but the remaining +1 is because (empirically) to match the behaviour of the untextured render path we need to draw lines one pixel wider
atlas->AALineRectIds.push_back(atlas->AddCustomRectRegular(width + 3, FONT_ATLAS_AA_LINE_TEX_HEIGHT));
}
}
void ImFontAtlasBuildAALinesTexData(ImFontAtlas* atlas)
{
IM_ASSERT(atlas->TexPixelsAlpha8 != NULL);
IM_ASSERT(atlas->TexUvAALines.size() == 0);
if (atlas->Flags & ImFontAtlasFlags_NoAALines)
return;
const int w = atlas->TexWidth;
const unsigned int max = atlas->AALineMaxWidth;
for (unsigned int n = 0; n < max; n++)
{
IM_ASSERT(atlas->AALineRectIds.size() > (int)n);
ImFontAtlas::CustomRect& r = atlas->CustomRects[atlas->AALineRectIds[n]];
IM_ASSERT(r.IsPacked());
// We fill as many lines as we were given, to allow for >1 lines being used to work around sampling weirdness
for (unsigned int y = 0; y < r.Height; y++)
{
unsigned char* write_ptr = &atlas->TexPixelsAlpha8[r.X + ((r.Y + y) * w)];
// Each line consists of two empty pixels at the ends, with a line of solid pixels in the middle
*(write_ptr++) = 0;
for (unsigned short x = 0; x < (r.Width - 2U); x++)
{
*(write_ptr++) = 0xFF;
}
*(write_ptr++) = 0;
}
ImVec2 uv0, uv1;
atlas->CalcCustomRectUV(&r, &uv0, &uv1);
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)
atlas->TexUvAALines.push_back(ImVec4(uv0.x, halfV, uv1.x, halfV));
}
}
void ImFontAtlasBuildFinish(ImFontAtlas* atlas)
{
// Render into our custom data blocks
IM_ASSERT(atlas->TexPixelsAlpha8 != NULL);
ImFontAtlasBuildRenderDefaultTexData(atlas);
// Render anti-aliased line textures
ImFontAtlasBuildAALinesTexData(atlas);
// Register custom rectangle glyphs
for (int i = 0; i < atlas->CustomRects.Size; i++)
{