QList<Quad> MeshTextureGraphicsItem::_split(const Quad& quad)
{
QList<Quad> quads;
QPointF a = quad.getVertex(0);
QPointF b = quad.getVertex(1);
QPointF c = quad.getVertex(2);
QPointF d = quad.getVertex(3);
QPointF ab = (a + b) * 0.5f;
QPointF bc = (b + c) * 0.5f;
QPointF cd = (c + d) * 0.5f;
QPointF ad = (a + d) * 0.5f;
QPointF abcd = (ab + cd) * 0.5f;
quads.append(Quad(a, ab, abcd, ad));
quads.append(Quad(ab, b, bc, abcd));
quads.append(Quad(abcd, bc, c, cd));
quads.append(Quad(ad, abcd, cd, d));
return quads;
}
void MeshTextureGraphicsItem::_drawQuad(const Texture& texture, const Quad& inputQuad, const Quad& outputQuad, float outputArea, float inputThreshod, float outputThreshold)
{
QPointF oa = mapFromScene(outputQuad.getVertex(0));
QPointF ob = mapFromScene(outputQuad.getVertex(1));
QPointF oc = mapFromScene(outputQuad.getVertex(2));
QPointF od = mapFromScene(outputQuad.getVertex(3));
QPointF ia = inputQuad.getVertex(0);
QPointF ib = inputQuad.getVertex(1);
QPointF ic = inputQuad.getVertex(2);
QPointF id = inputQuad.getVertex(3);
// compute the dot products for the polygon
float outputV1dotV2 = QPointF::dotProduct(oa-ob, oc-ob);
float outputV3dotV4 = QPointF::dotProduct(oc-od, oa-od);
float outputV1dotV4 = QPointF::dotProduct(oa-ob, oa-od);
float outputV2dotV3 = QPointF::dotProduct(oc-ob, oc-od);
// compute the dot products for the texture
float inputV1dotV2 = QPointF::dotProduct(ia-ib, ic-ib);
float inputV3dotV4 = QPointF::dotProduct(ic-id, ia-id);
float inputV1dotV4 = QPointF::dotProduct(ia-ib, ia-id);
float inputV2dotV3 = QPointF::dotProduct(ic-ib, ic-id);
// Stopping criterion.
if (outputArea < 200 ||
(fabs(outputV1dotV2 - outputV3dotV4) < outputThreshold &&
fabs(outputV1dotV4 - outputV2dotV3) < outputThreshold &&
fabs(inputV1dotV2 - inputV3dotV4) < inputThreshod &&
fabs(inputV1dotV4 - inputV2dotV3) < inputThreshod))
{
glBegin(GL_QUADS);
for (int i = 0; i < outputQuad.nVertices(); i++)
{
Util::setGlTexPoint(texture, inputQuad.getVertex(i), mapFromScene(outputQuad.getVertex(i)));
}
glEnd();
}
else // subdivide
{
QList<Quad> inputSubQuads = _split(inputQuad);
QList<Quad> outputSubQuads = _split(outputQuad);
for (int i = 0; i < inputSubQuads.size(); i++)
{
_drawQuad(texture, inputSubQuads[i], outputSubQuads[i], outputArea*0.25, inputThreshod, outputThreshold);
}
}
}