// Mesh the area into nodes and elements or return error message if fails
// assumes edges already oriented correctly
const char *Area::MeshElements(void)
{
// exactly 2 paths will be for an interface
if(numPaths==2)
return MeshInterface();
// Must be 4-sided area. In future should support more
if(numPaths!=4)
return "Code can only mesh quadrilateral areas (4 paths) or interfaces (2 paths).";
// cannot be interface elements
if(theElems->InterfaceElements())
return "Areas cannot be meshed into interface elements.";
// must be connected
if(edges[numPaths-1]->LastKeypoint()!=edges[0]->FirstKeypoint())
return "Area does not define enclosed area.";
// is element provided
if(theElems->CurrentElemID()<0)
return "No element type defined for area.";
// Check intervals
if(!CheckIntervals())
return "Number of intervals on sides of the area are not valid";
// Check path usage
if(!PathsAvailable())
return "Paths cannot be meshed into more than 2 areas";
// Check ccw
if(SignedArea()<0.)
return "The paths must circumnavigate the area in a counter-clockwise direction";
// create function if being used
if(angleExpr!=NULL)
{ if(!CreateFunction(angleExpr))
return "The expression for material angle is not a valid function";
}
// mesh the error
return MeshArea();
}
void OcclusionBuffer::DrawTriangle(Vector4* vertices)
{
unsigned clipMask = 0;
unsigned andClipMask = 0;
bool drawOk = false;
Vector3 projected[3];
// Build the clip plane mask for the triangle
for (unsigned i = 0; i < 3; ++i)
{
unsigned vertexClipMask = 0;
if (vertices[i].x_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_X_POS;
if (vertices[i].x_ < -vertices[i].w_)
vertexClipMask |= CLIPMASK_X_NEG;
if (vertices[i].y_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_Y_POS;
if (vertices[i].y_ < -vertices[i].w_)
vertexClipMask |= CLIPMASK_Y_NEG;
if (vertices[i].z_ > vertices[i].w_)
vertexClipMask |= CLIPMASK_Z_POS;
if (vertices[i].z_ < 0.0f)
vertexClipMask |= CLIPMASK_Z_NEG;
clipMask |= vertexClipMask;
if (!i)
andClipMask = vertexClipMask;
else
andClipMask &= vertexClipMask;
}
// If triangle is fully behind any clip plane, can reject quickly
if (andClipMask)
return;
// Check if triangle is fully inside
if (!clipMask)
{
projected[0] = ViewportTransform(vertices[0]);
projected[1] = ViewportTransform(vertices[1]);
projected[2] = ViewportTransform(vertices[2]);
bool clockwise = SignedArea(projected[0], projected[1], projected[2]) < 0.0f;
if (cullMode_ == CULL_NONE || (cullMode_ == CULL_CCW && clockwise) || (cullMode_ == CULL_CW && !clockwise))
{
DrawTriangle2D(projected, clockwise);
drawOk = true;
}
}
else
{
bool triangles[64];
// Initial triangle
triangles[0] = true;
unsigned numTriangles = 1;
if (clipMask & CLIPMASK_X_POS)
ClipVertices(Vector4(-1.0f, 0.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_X_NEG)
ClipVertices(Vector4(1.0f, 0.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Y_POS)
ClipVertices(Vector4(0.0f, -1.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Y_NEG)
ClipVertices(Vector4(0.0f, 1.0f, 0.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Z_POS)
ClipVertices(Vector4(0.0f, 0.0f, -1.0f, 1.0f), vertices, triangles, numTriangles);
if (clipMask & CLIPMASK_Z_NEG)
ClipVertices(Vector4(0.0f, 0.0f, 1.0f, 0.0f), vertices, triangles, numTriangles);
// Draw each accepted triangle
for (unsigned i = 0; i < numTriangles; ++i)
{
if (triangles[i])
{
unsigned index = i * 3;
projected[0] = ViewportTransform(vertices[index]);
projected[1] = ViewportTransform(vertices[index + 1]);
projected[2] = ViewportTransform(vertices[index + 2]);
bool clockwise = SignedArea(projected[0], projected[1], projected[2]) < 0.0f;
if (cullMode_ == CULL_NONE || (cullMode_ == CULL_CCW && clockwise) || (cullMode_ == CULL_CW && !clockwise))
{
DrawTriangle2D(projected, clockwise);
drawOk = true;
}
}
}
}
if (drawOk)
++numTriangles_;
}
