mirror of
https://github.com/love2d/love.git
synced 2026-08-15 15:51:12 +02:00
Alex Szpakowski
382 lines
10 KiB
C++
382 lines
10 KiB
C++
/**
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* Copyright (c) 2006-2014 LOVE Development Team
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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**/
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#include <algorithm>
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// LOVE
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#include "Polyline.h"
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// OpenGL
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#include "OpenGL.h"
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// treat adjacent segments with angles between their directions <5 degree as straight
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static const float LINES_PARALLEL_EPS = 0.05f;
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namespace love
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{
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namespace graphics
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{
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namespace opengl
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{
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void Polyline::render(const float *coords, size_t count, size_t size_hint, float halfwidth, float pixel_size, bool draw_overdraw)
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{
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static std::vector<Vector> anchors;
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anchors.clear();
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anchors.reserve(size_hint);
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static std::vector<Vector> normals;
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normals.clear();
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normals.reserve(size_hint);
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// prepare vertex arrays
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if (draw_overdraw)
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halfwidth -= pixel_size * .3;
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// compute sleeve
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bool is_looping = (coords[0] == coords[count - 2]) && (coords[1] == coords[count - 1]);
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Vector s;
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if (!is_looping) // virtual starting point at second point mirrored on first point
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s = Vector(coords[2] - coords[0], coords[3] - coords[1]);
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else // virtual starting point at last vertex
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s = Vector(coords[0] - coords[count - 4], coords[1] - coords[count - 3]);
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float len_s = s.getLength();
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Vector ns = s.getNormal(halfwidth / len_s);
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Vector q, r(coords[0], coords[1]);
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for (size_t i = 0; i + 3 < count; i += 2)
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{
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q = r;
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r = Vector(coords[i + 2], coords[i + 3]);
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renderEdge(anchors, normals, s, len_s, ns, q, r, halfwidth);
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}
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q = r;
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r = is_looping ? Vector(coords[2], coords[3]) : r + s;
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renderEdge(anchors, normals, s, len_s, ns, q, r, halfwidth);
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vertex_count = normals.size();
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vertices = new Vector[vertex_count];
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for (size_t i = 0; i < vertex_count; ++i)
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vertices[i] = anchors[i] + normals[i];
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if (draw_overdraw)
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render_overdraw(normals, pixel_size, is_looping);
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}
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void NoneJoinPolyline::renderEdge(std::vector<Vector> &anchors, std::vector<Vector> &normals,
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Vector &s, float &len_s, Vector &ns,
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const Vector &q, const Vector &r, float hw)
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{
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anchors.push_back(q);
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anchors.push_back(q);
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normals.push_back(ns);
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normals.push_back(-ns);
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s = (r - q);
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len_s = s.getLength();
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ns = s.getNormal(hw / len_s);
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anchors.push_back(q);
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anchors.push_back(q);
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normals.push_back(-ns);
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normals.push_back(ns);
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}
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/** Calculate line boundary points.
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*
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* Sketch:
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*
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* u1
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* -------------+---...___
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* | ```'''-- ---
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* p- - - - - - q- - . _ _ | w/2
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* | ` ' ' r +
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* -------------+---...___ | w/2
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* u2 ```'''-- ---
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*
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* u1 and u2 depend on four things:
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* - the half line width w/2
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* - the previous line vertex p
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* - the current line vertex q
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* - the next line vertex r
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*
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* u1/u2 are the intersection points of the parallel lines to p-q and q-r,
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* i.e. the point where
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*
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* (q + w/2 * ns) + lambda * (q - p) = (q + w/2 * nt) + mu * (r - q) (u1)
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* (q - w/2 * ns) + lambda * (q - p) = (q - w/2 * nt) + mu * (r - q) (u2)
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*
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* with nt,nt being the normals on the segments s = p-q and t = q-r,
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*
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* ns = perp(s) / |s|
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* nt = perp(t) / |t|.
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*
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* Using the linear equation system (similar for u2)
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*
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* q + w/2 * ns + lambda * s - (q + w/2 * nt + mu * t) = 0 (u1)
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* <=> q-q + lambda * s - mu * t = (nt - ns) * w/2
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* <=> lambda * s - mu * t = (nt - ns) * w/2
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*
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* the intersection points can be efficiently calculated using Cramer's rule.
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*/
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void MiterJoinPolyline::renderEdge(std::vector<Vector> &anchors, std::vector<Vector> &normals,
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Vector &s, float &len_s, Vector &ns,
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const Vector &q, const Vector &r, float hw)
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{
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Vector t = (r - q);
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float len_t = t.getLength();
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Vector nt = t.getNormal(hw / len_t);
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anchors.push_back(q);
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anchors.push_back(q);
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float det = s ^ t;
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if (fabs(det) / (len_s * len_t) < LINES_PARALLEL_EPS && s * t > 0)
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{
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// lines parallel, compute as u1 = q + ns * w/2, u2 = q - ns * w/2
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normals.push_back(ns);
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normals.push_back(-ns);
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}
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else
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{
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// cramers rule
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float lambda = ((nt - ns) ^ t) / det;
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Vector d = ns + s * lambda;
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normals.push_back(d);
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normals.push_back(-d);
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}
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s = t;
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ns = nt;
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len_s = len_t;
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}
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/** Calculate line boundary points.
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*
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* Sketch:
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*
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* uh1___uh2
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* .' '.
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* .' q '.
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* .' ' ' '.
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*.' ' .'. ' '.
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* ' .' ul'. '
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* p .' '. r
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*
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*
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* ul can be found as above, uh1 and uh2 are much simpler:
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*
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* uh1 = q + ns * w/2, uh2 = q + nt * w/2
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*/
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void BevelJoinPolyline::renderEdge(std::vector<Vector> &anchors, std::vector<Vector> &normals,
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Vector &s, float &len_s, Vector &ns,
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const Vector &q, const Vector &r, float hw)
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{
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Vector t = (r - q);
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float len_t = t.getLength();
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float det = s ^ t;
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if (fabs(det) / (len_s * len_t) < LINES_PARALLEL_EPS && s * t > 0)
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{
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// lines parallel, compute as u1 = q + ns * w/2, u2 = q - ns * w/2
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Vector n = t.getNormal(hw / len_t);
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anchors.push_back(q);
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anchors.push_back(q);
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normals.push_back(n);
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normals.push_back(-n);
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s = t;
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len_s = len_t;
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return; // early out
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}
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// cramers rule
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Vector nt= t.getNormal(hw / len_t);
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float lambda = ((nt - ns) ^ t) / det;
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Vector d = ns + s * lambda;
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anchors.push_back(q);
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anchors.push_back(q);
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anchors.push_back(q);
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anchors.push_back(q);
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if (det > 0) // 'left' turn -> intersection on the top
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{
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normals.push_back(d);
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normals.push_back(-ns);
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normals.push_back(d);
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normals.push_back(-nt);
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}
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else
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{
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normals.push_back(ns);
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normals.push_back(-d);
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normals.push_back(nt);
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normals.push_back(-d);
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}
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s = t;
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len_s = len_t;
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ns = nt;
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}
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void Polyline::render_overdraw(const std::vector<Vector> &normals, float pixel_size, bool is_looping)
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{
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overdraw_vertex_count = 2 * vertex_count + (is_looping ? 0 : 2);
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overdraw = new Vector[overdraw_vertex_count];
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// upper segment
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for (size_t i = 0; i + 1 < vertex_count; i += 2)
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{
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overdraw[i] = vertices[i];
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overdraw[i+1] = vertices[i] + normals[i] * (pixel_size / normals[i].getLength());
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}
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// lower segment
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for (size_t i = 0; i + 1 < vertex_count; i += 2)
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{
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size_t k = vertex_count - i - 1;
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overdraw[vertex_count + i] = vertices[k];
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overdraw[vertex_count + i+1] = vertices[k] + normals[k] * (pixel_size / normals[i].getLength());
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}
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// if not looping, the outer overdraw vertices need to be displaced
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// to cover the line endings, i.e.:
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// +- - - - //- - + +- - - - - //- - - +
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// +-------//-----+ : +-------//-----+ :
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// | core // line | --> : | core // line | :
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// +-----//-------+ : +-----//-------+ :
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// +- - //- - - - + +- - - //- - - - - +
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if (!is_looping)
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{
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// left edge
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Vector spacer = (overdraw[1] - overdraw[3]);
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spacer.normalize(pixel_size);
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overdraw[1] += spacer;
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overdraw[overdraw_vertex_count - 3] += spacer;
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// right edge
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spacer = (overdraw[vertex_count-1] - overdraw[vertex_count-3]);
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spacer.normalize(pixel_size);
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overdraw[vertex_count-1] += spacer;
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overdraw[vertex_count+1] += spacer;
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// we need to draw two more triangles to close the
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// overdraw at the line start.
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overdraw[overdraw_vertex_count-2] = overdraw[0];
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overdraw[overdraw_vertex_count-1] = overdraw[1];
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}
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}
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void NoneJoinPolyline::render_overdraw(const std::vector<Vector> &/*normals*/, float pixel_size, bool /*is_looping*/)
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{
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overdraw_vertex_count = 4 * (vertex_count-2); // less than ideal
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overdraw = new Vector[overdraw_vertex_count];
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for (size_t i = 2; i + 3 < vertex_count; i += 4)
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{
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Vector s = vertices[i] - vertices[i+3];
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Vector t = vertices[i] - vertices[i+1];
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s.normalize(pixel_size);
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t.normalize(pixel_size);
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const size_t k = 4 * (i - 2);
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overdraw[k ] = vertices[i];
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overdraw[k+1] = vertices[i] + s + t;
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overdraw[k+2] = vertices[i+1] + s - t;
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overdraw[k+3] = vertices[i+1];
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overdraw[k+4] = vertices[i+1];
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overdraw[k+5] = vertices[i+1] + s - t;
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overdraw[k+6] = vertices[i+2] - s - t;
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overdraw[k+7] = vertices[i+2];
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overdraw[k+8] = vertices[i+2];
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overdraw[k+9] = vertices[i+2] - s - t;
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overdraw[k+10] = vertices[i+3] - s + t;
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overdraw[k+11] = vertices[i+3];
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overdraw[k+12] = vertices[i+3];
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overdraw[k+13] = vertices[i+3] - s + t;
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overdraw[k+14] = vertices[i] + s + t;
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overdraw[k+15] = vertices[i];
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}
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}
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Polyline::~Polyline()
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{
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if (vertices)
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delete[] vertices;
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if (overdraw)
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delete[] overdraw;
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}
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void Polyline::draw()
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{
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gl.prepareDraw();
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// draw the core line
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gl.bindTexture(0);
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glEnableClientState(GL_VERTEX_ARRAY);
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glVertexPointer(2, GL_FLOAT, 0, (const GLvoid *)vertices);
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glDrawArrays(draw_mode, 0, vertex_count);
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if (overdraw)
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{
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// prepare colors:
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Color c = gl.getColor();
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Color *colors = new Color[overdraw_vertex_count];
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fill_color_array(colors, c);
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glEnableClientState(GL_COLOR_ARRAY);
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glColorPointer(4, GL_UNSIGNED_BYTE, 0, colors);
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glVertexPointer(2, GL_FLOAT, 0, (const GLvoid *)overdraw);
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glDrawArrays(draw_mode, 0, overdraw_vertex_count);
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glDisableClientState(GL_COLOR_ARRAY);
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delete[] colors;
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gl.setColor(c);
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}
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glDisableClientState(GL_VERTEX_ARRAY);
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}
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void Polyline::fill_color_array(Color *colors, const Color &c)
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{
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for (size_t i = 0; i < overdraw_vertex_count; ++i)
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{
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colors[i] = c;
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// avoids branching. equiv to if (i%2 == 1) colors[i].a = 0;
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colors[i].a *= GLubyte((i+1) % 2);
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}
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}
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void NoneJoinPolyline::fill_color_array(Color *colors, const Color &c)
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{
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for (size_t i = 0; i < overdraw_vertex_count; ++i)
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{
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colors[i] = c;
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// if (i % 4 == 1 || i % 4 == 2) colors[i].a = 0
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colors[i].a *= GLubyte((i+1) % 4 < 2);
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}
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}
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} // opengl
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} // graphics
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} // love
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