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godot/scene/2d/line_builder.cpp

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/**************************************************************************/
/* line_builder.cpp */
/**************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/**************************************************************************/
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
/* */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the */
/* "Software"), to deal in the Software without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of the Software, and to */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
/**************************************************************************/
#include "line_builder.h"
#include "core/math/geometry_2d.h"
// Utility method.
static inline Vector2 interpolate(const Rect2 &r, const Vector2 &v) {
return Vector2(
Math::lerp(r.position.x, r.position.x + r.get_size().x, v.x),
Math::lerp(r.position.y, r.position.y + r.get_size().y, v.y));
}
LineBuilder::LineBuilder() {
}
void LineBuilder::build() {
// Need at least 2 points to draw a line, so clear the output and return.
if (points.size() < 2) {
vertices.clear();
colors.clear();
indices.clear();
uvs.clear();
return;
}
ERR_FAIL_COND(tile_aspect <= 0.f);
const float hw = width / 2.f;
const float hw_sq = hw * hw;
const float sharp_limit_sq = sharp_limit * sharp_limit;
const int point_count = points.size();
const bool wrap_around = closed && point_count > 2;
_interpolate_color = gradient != nullptr;
const bool retrieve_curve = curve != nullptr;
const bool distance_required = _interpolate_color || retrieve_curve ||
texture_mode == Line2D::LINE_TEXTURE_TILE ||
texture_mode == Line2D::LINE_TEXTURE_STRETCH;
// Initial values
Vector2 pos0 = points[0];
Vector2 pos1 = points[1];
Vector2 f0 = (pos1 - pos0).normalized();
Vector2 u0 = f0.orthogonal();
Vector2 pos_up0 = pos0;
Vector2 pos_down0 = pos0;
Color color0;
Color color1;
float current_distance0 = 0.f;
float current_distance1 = 0.f;
float total_distance = 0.f;
float width_factor = 1.f;
float modified_hw = hw;
if (retrieve_curve) {
width_factor = curve->sample_baked(0.f);
modified_hw = hw * width_factor;
}
if (distance_required) {
// Calculate the total distance.
for (int i = 1; i < point_count; ++i) {
total_distance += points[i].distance_to(points[i - 1]);
}
if (wrap_around) {
total_distance += points[point_count - 1].distance_to(pos0);
} else {
// Adjust the total distance.
// The line's outer length may be a little higher due to the end caps.
if (begin_cap_mode == Line2D::LINE_CAP_BOX || begin_cap_mode == Line2D::LINE_CAP_ROUND) {
total_distance += modified_hw;
}
if (end_cap_mode == Line2D::LINE_CAP_BOX || end_cap_mode == Line2D::LINE_CAP_ROUND) {
if (retrieve_curve) {
total_distance += hw * curve->sample_baked(1.f);
} else {
total_distance += hw;
}
}
}
}
if (_interpolate_color) {
color0 = gradient->get_color(0);
} else {
colors.push_back(default_color);
}
float uvx0 = 0.f;
float uvx1 = 0.f;
pos_up0 += u0 * modified_hw;
pos_down0 -= u0 * modified_hw;
// Begin cap
if (!wrap_around) {
if (begin_cap_mode == Line2D::LINE_CAP_BOX) {
// Push back first vertices a little bit.
pos_up0 -= f0 * modified_hw;
pos_down0 -= f0 * modified_hw;
current_distance0 += modified_hw;
current_distance1 = current_distance0;
} else if (begin_cap_mode == Line2D::LINE_CAP_ROUND) {
if (texture_mode == Line2D::LINE_TEXTURE_TILE) {
uvx0 = width_factor * 0.5f / tile_aspect;
} else if (texture_mode == Line2D::LINE_TEXTURE_STRETCH) {
uvx0 = width * width_factor / total_distance;
}
new_arc(pos0, pos_up0 - pos0, -Math_PI, color0, Rect2(0.f, 0.f, uvx0 * 2, 1.f));
current_distance0 += modified_hw;
current_distance1 = current_distance0;
}
strip_begin(pos_up0, pos_down0, color0, uvx0);
}
/*
* pos_up0 ------------- pos_up1 --------------------
* | |
* pos0 - - - - - - - - - pos1 - - - - - - - - - pos2
* | |
* pos_down0 ------------ pos_down1 ------------------
*
* i-1 i i+1
*/
// http://labs.hyperandroid.com/tag/opengl-lines
// (not the same implementation but visuals help a lot)
// If the polyline wraps around, then draw two more segments with joints:
// The last one, which should normally end with an end cap, and the one that matches the end and the beginning.
int segments_count = wrap_around ? point_count : (point_count - 2);
// The wraparound case starts with a "fake walk" from the end of the polyline
// to its beginning, so that its first joint is correct, without drawing anything.
int first_point = wrap_around ? -1 : 1;
// If the line wraps around, these variables will be used for the final segment.
Vector2 first_pos_up, first_pos_down;
bool is_first_joint_sharp = false;
// For each additional segment
for (int i = first_point; i <= segments_count; ++i) {
pos1 = points[(i == -1) ? point_count - 1 : i % point_count]; // First point.
Vector2 pos2 = points[(i + 1) % point_count]; // Second point.
Vector2 f1 = (pos2 - pos1).normalized();
Vector2 u1 = f1.orthogonal();
// Determine joint orientation.
float dp = u0.dot(f1);
const Orientation orientation = (dp > 0.f ? UP : DOWN);
if (distance_required && i >= 1) {
current_distance1 += pos0.distance_to(pos1);
}
if (_interpolate_color) {
color1 = gradient->get_color_at_offset(current_distance1 / total_distance);
}
if (retrieve_curve) {
width_factor = curve->sample_baked(current_distance1 / total_distance);
modified_hw = hw * width_factor;
}
Vector2 inner_normal0 = u0 * modified_hw;
Vector2 inner_normal1 = u1 * modified_hw;
if (orientation == DOWN) {
inner_normal0 = -inner_normal0;
inner_normal1 = -inner_normal1;
}
/*
* ---------------------------
* /
* 0 / 1
* / /
* --------------------x------ /
* / / (here shown with orientation == DOWN)
* / /
* / /
* / /
* 2 /
* /
*/
// Find inner intersection at the joint.
Vector2 corner_pos_in, corner_pos_out;
bool is_intersecting = Geometry2D::segment_intersects_segment(
pos0 + inner_normal0, pos1 + inner_normal0,
pos1 + inner_normal1, pos2 + inner_normal1,
&corner_pos_in);
if (is_intersecting) {
// Inner parts of the segments intersect.
corner_pos_out = 2.f * pos1 - corner_pos_in;
} else {
// No intersection, segments are too sharp or they overlap.
corner_pos_in = pos1 + inner_normal0;
corner_pos_out = pos1 - inner_normal0;
}
Vector2 corner_pos_up, corner_pos_down;
if (orientation == UP) {
corner_pos_up = corner_pos_in;
corner_pos_down = corner_pos_out;
} else {
corner_pos_up = corner_pos_out;
corner_pos_down = corner_pos_in;
}
Line2D::LineJointMode current_joint_mode = joint_mode;
Vector2 pos_up1, pos_down1;
if (is_intersecting) {
// Fallback on bevel if sharp angle is too high (because it would produce very long miters).
float width_factor_sq = width_factor * width_factor;
if (current_joint_mode == Line2D::LINE_JOINT_SHARP && corner_pos_out.distance_squared_to(pos1) / (hw_sq * width_factor_sq) > sharp_limit_sq) {
current_joint_mode = Line2D::LINE_JOINT_BEVEL;
}
if (current_joint_mode == Line2D::LINE_JOINT_SHARP) {
// In this case, we won't create joint geometry,
// The previous and next line quads will directly share an edge.
pos_up1 = corner_pos_up;
pos_down1 = corner_pos_down;
} else {
// Bevel or round
if (orientation == UP) {
pos_up1 = corner_pos_up;
pos_down1 = pos1 - u0 * modified_hw;
} else {
pos_up1 = pos1 + u0 * modified_hw;
pos_down1 = corner_pos_down;
}
}
} else {
// No intersection: fallback
if (current_joint_mode == Line2D::LINE_JOINT_SHARP) {
// There is no fallback implementation for LINE_JOINT_SHARP so switch to the LINE_JOINT_BEVEL.
current_joint_mode = Line2D::LINE_JOINT_BEVEL;
}
pos_up1 = corner_pos_up;
pos_down1 = corner_pos_down;
}
// Triangles are clockwise.
if (texture_mode == Line2D::LINE_TEXTURE_TILE) {
uvx1 = current_distance1 / (width * tile_aspect);
} else if (texture_mode == Line2D::LINE_TEXTURE_STRETCH) {
uvx1 = current_distance1 / total_distance;
}
// Swap vars for use in the next line.
color0 = color1;
u0 = u1;
f0 = f1;
pos0 = pos1;
if (is_intersecting) {
if (current_joint_mode == Line2D::LINE_JOINT_SHARP) {
pos_up0 = pos_up1;
pos_down0 = pos_down1;
} else {
if (orientation == UP) {
pos_up0 = corner_pos_up;
pos_down0 = pos1 - u1 * modified_hw;
} else {
pos_up0 = pos1 + u1 * modified_hw;
pos_down0 = corner_pos_down;
}
}
} else {
pos_up0 = pos1 + u1 * modified_hw;
pos_down0 = pos1 - u1 * modified_hw;
}
// End the "fake pass" in the closed line case before the drawing subroutine.
if (i == -1) {
continue;
}
// For wrap-around polylines, store some kind of start positions of the first joint for the final connection.
if (wrap_around && i == 0) {
Vector2 first_pos_center = (pos_up1 + pos_down1) / 2;
float lerp_factor = 1.0 / width_factor;
first_pos_up = first_pos_center.lerp(pos_up1, lerp_factor);
first_pos_down = first_pos_center.lerp(pos_down1, lerp_factor);
is_first_joint_sharp = current_joint_mode == Line2D::LINE_JOINT_SHARP;
}
// Add current line body quad.
if (wrap_around && retrieve_curve && !is_first_joint_sharp && i == segments_count) {
// If the width curve is not seamless, we might need to fetch the line's start points to use them for the final connection.
Vector2 first_pos_center = (first_pos_up + first_pos_down) / 2;
strip_add_quad(first_pos_center.lerp(first_pos_up, width_factor), first_pos_center.lerp(first_pos_down, width_factor), color1, uvx1);
return;
} else {
strip_add_quad(pos_up1, pos_down1, color1, uvx1);
}
// From this point, bu0 and bd0 concern the next segment.
// Add joint geometry.
if (current_joint_mode != Line2D::LINE_JOINT_SHARP) {
/* ________________ cbegin
* / \
* / \
* ____________/_ _ _\ cend
* | |
* | |
* | |
*/
Vector2 cbegin, cend;
if (orientation == UP) {
cbegin = pos_down1;
cend = pos_down0;
} else {
cbegin = pos_up1;
cend = pos_up0;
}
if (current_joint_mode == Line2D::LINE_JOINT_BEVEL && !(wrap_around && i == segments_count)) {
strip_add_tri(cend, orientation);
} else if (current_joint_mode == Line2D::LINE_JOINT_ROUND && !(wrap_around && i == segments_count)) {
Vector2 vbegin = cbegin - pos1;
Vector2 vend = cend - pos1;
// We want to use vbegin.angle_to(vend) below, which evaluates to
// Math::atan2(vbegin.cross(vend), vbegin.dot(vend)) but we need to
// calculate this ourselves as we need to check if the cross product
// in that calculation ends up being -0.f and flip it if so, effectively
// flipping the resulting angle_delta to not return -PI but +PI instead
float cross_product = vbegin.cross(vend);
float dot_product = vbegin.dot(vend);
// Note that we're comparing against -0.f for clarity but 0.f would
// match as well, therefore we need the explicit signbit check too.
if (cross_product == -0.f && signbit(cross_product)) {
cross_product = 0.f;
}
float angle_delta = Math::atan2(cross_product, dot_product);
strip_add_arc(pos1, angle_delta, orientation);
}
if (!is_intersecting) {
// In this case the joint is too corrupted to be re-used,
// start again the strip with fallback points
strip_begin(pos_up0, pos_down0, color1, uvx1);
}
}
}
// Draw the last (or only) segment, with its end cap logic.
if (!wrap_around) {
pos1 = points[point_count - 1];
if (distance_required) {
current_distance1 += pos0.distance_to(pos1);
}
if (_interpolate_color) {
color1 = gradient->get_color(gradient->get_point_count() - 1);
}
if (retrieve_curve) {
width_factor = curve->sample_baked(1.f);
modified_hw = hw * width_factor;
}
Vector2 pos_up1 = pos1 + u0 * modified_hw;
Vector2 pos_down1 = pos1 - u0 * modified_hw;
// Add extra distance for a box end cap.
if (end_cap_mode == Line2D::LINE_CAP_BOX) {
pos_up1 += f0 * modified_hw;
pos_down1 += f0 * modified_hw;
current_distance1 += modified_hw;
}
if (texture_mode == Line2D::LINE_TEXTURE_TILE) {
uvx1 = current_distance1 / (width * tile_aspect);
} else if (texture_mode == Line2D::LINE_TEXTURE_STRETCH) {
uvx1 = current_distance1 / total_distance;
}
strip_add_quad(pos_up1, pos_down1, color1, uvx1);
// Custom drawing for a round end cap.
if (end_cap_mode == Line2D::LINE_CAP_ROUND) {
// Note: color is not used in case we don't interpolate.
Color color = _interpolate_color ? gradient->get_color(gradient->get_point_count() - 1) : Color(0, 0, 0);
float dist = 0;
if (texture_mode == Line2D::LINE_TEXTURE_TILE) {
dist = width_factor / tile_aspect;
} else if (texture_mode == Line2D::LINE_TEXTURE_STRETCH) {
dist = width * width_factor / total_distance;
}
new_arc(pos1, pos_up1 - pos1, Math_PI, color, Rect2(uvx1 - 0.5f * dist, 0.f, dist, 1.f));
}
}
}
void LineBuilder::strip_begin(Vector2 up, Vector2 down, Color color, float uvx) {
int vi = vertices.size();
vertices.push_back(up);
vertices.push_back(down);
if (_interpolate_color) {
colors.push_back(color);
colors.push_back(color);
}
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
uvs.push_back(Vector2(uvx, 0.f));
uvs.push_back(Vector2(uvx, 1.f));
}
_last_index[UP] = vi;
_last_index[DOWN] = vi + 1;
}
void LineBuilder::strip_add_quad(Vector2 up, Vector2 down, Color color, float uvx) {
int vi = vertices.size();
vertices.push_back(up);
vertices.push_back(down);
if (_interpolate_color) {
colors.push_back(color);
colors.push_back(color);
}
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
uvs.push_back(Vector2(uvx, 0.f));
uvs.push_back(Vector2(uvx, 1.f));
}
indices.push_back(_last_index[UP]);
indices.push_back(vi + 1);
indices.push_back(_last_index[DOWN]);
indices.push_back(_last_index[UP]);
indices.push_back(vi);
indices.push_back(vi + 1);
_last_index[UP] = vi;
_last_index[DOWN] = vi + 1;
}
void LineBuilder::strip_add_tri(Vector2 up, Orientation orientation) {
int vi = vertices.size();
vertices.push_back(up);
if (_interpolate_color) {
colors.push_back(colors[colors.size() - 1]);
}
Orientation opposite_orientation = orientation == UP ? DOWN : UP;
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
// UVs are just one slice of the texture all along
// (otherwise we can't share the bottom vertex)
uvs.push_back(uvs[_last_index[opposite_orientation]]);
}
indices.push_back(_last_index[opposite_orientation]);
indices.push_back(vi);
indices.push_back(_last_index[orientation]);
_last_index[opposite_orientation] = vi;
}
void LineBuilder::strip_add_arc(Vector2 center, float angle_delta, Orientation orientation) {
// Take the two last vertices and extrude an arc made of triangles
// that all share one of the initial vertices
Orientation opposite_orientation = orientation == UP ? DOWN : UP;
Vector2 vbegin = vertices[_last_index[opposite_orientation]] - center;
float radius = vbegin.length();
float angle_step = Math_PI / static_cast<float>(round_precision);
float steps = Math::abs(angle_delta) / angle_step;
if (angle_delta < 0.f) {
angle_step = -angle_step;
}
float t = Vector2(1, 0).angle_to(vbegin);
float end_angle = t + angle_delta;
Vector2 rpos(0, 0);
// Arc vertices
for (int ti = 0; ti < steps; ++ti, t += angle_step) {
rpos = center + Vector2(Math::cos(t), Math::sin(t)) * radius;
strip_add_tri(rpos, orientation);
}
// Last arc vertex
rpos = center + Vector2(Math::cos(end_angle), Math::sin(end_angle)) * radius;
strip_add_tri(rpos, orientation);
}
void LineBuilder::new_arc(Vector2 center, Vector2 vbegin, float angle_delta, Color color, Rect2 uv_rect) {
// Make a standalone arc that doesn't use existing vertices,
// with undistorted UVs from within a square section
float radius = vbegin.length();
float angle_step = Math_PI / static_cast<float>(round_precision);
float steps = Math::abs(angle_delta) / angle_step;
if (angle_delta < 0.f) {
angle_step = -angle_step;
}
float t = Vector2(1, 0).angle_to(vbegin);
float end_angle = t + angle_delta;
Vector2 rpos(0, 0);
float tt_begin = -Math_PI / 2.0f;
float tt = tt_begin;
// Center vertice
int vi = vertices.size();
vertices.push_back(center);
if (_interpolate_color) {
colors.push_back(color);
}
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
uvs.push_back(interpolate(uv_rect, Vector2(0.5f, 0.5f)));
}
// Arc vertices
for (int ti = 0; ti < steps; ++ti, t += angle_step) {
Vector2 sc = Vector2(Math::cos(t), Math::sin(t));
rpos = center + sc * radius;
vertices.push_back(rpos);
if (_interpolate_color) {
colors.push_back(color);
}
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
Vector2 tsc = Vector2(Math::cos(tt), Math::sin(tt));
uvs.push_back(interpolate(uv_rect, 0.5f * (tsc + Vector2(1.f, 1.f))));
tt += angle_step;
}
}
// Last arc vertex
Vector2 sc = Vector2(Math::cos(end_angle), Math::sin(end_angle));
rpos = center + sc * radius;
vertices.push_back(rpos);
if (_interpolate_color) {
colors.push_back(color);
}
if (texture_mode != Line2D::LINE_TEXTURE_NONE) {
tt = tt_begin + angle_delta;
Vector2 tsc = Vector2(Math::cos(tt), Math::sin(tt));
uvs.push_back(interpolate(uv_rect, 0.5f * (tsc + Vector2(1.f, 1.f))));
}
// Make up triangles
int vi0 = vi;
for (int ti = 0; ti < steps; ++ti) {
indices.push_back(vi0);
indices.push_back(++vi);
indices.push_back(vi + 1);
}
}
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