How to achieve similar functionality to Matlab's fill3 function and output to SVG in ILNumerics - ilnumerics

Question

I am trying to achieve something similar to Matlab's fill3 function in ILNumerics and output to an SVG file. fill3 allows you to plot 3d shapes with a solid fill color and specify an edge color for the shapes that you are plotting.
The code that I am using to plot the shapes is as follows:
var scene = new ILScene();
scene.Camera.Add(new ILTriangles
{
Positions = new float[,]
{
{-1, -1, -1}, {-1, 1, -1}, {0, 1, 0},
{-1, -1, -1}, {0, 1, 0}, {0, -1, 0},
{0, -1, 0}, {0, 1, 0}, {1, 1, -1},
{0, -1, 0}, {1, 1, -1}, {1, -1, -1}
},
Color = Color.Red,
AutoNormals = false
});
scene.Camera.Add(new ILLines
{
Positions = new float[,]
{
{-1, -1, -1}, {-1, 1, -1}, {0, 1, 0}, {0, -1, 0}
},
Indices = new[] {0, 1, 1, 2, 2, 3, 3, 0},
Color = Color.Black,
Width = 3
});
scene.Camera.Add(new ILLines
{
Positions = new float[,]
{
{0, -1, 0}, {0, 1, 0}, {1, 1, -1}, {1, -1, -1}
},
Indices = new[] { 0, 1, 1, 2, 2, 3, 3, 0 },
Color = Color.Black,
Width = 3
});
ilPanel1.Scene = scene;
The code that I am using to output to SVG is as follows:
using (var fs = new FileStream(#"C:\test.svg", FileMode.Create))
{
new ILSVGDriver(fs, scene: ilPanel1.GetCurrentScene(), width: 500, height: 600).Render();
}
The result looks perfect in the ILPanel, but when rendered to an SVG the triangle shapes seem to step on/cover the lines.
Is there another way to go about this to achieve what I am looking for? Thanks!

Answer 1

ILNumerics renders all filled shapes based on triangles. This gives the most flexibility and corresponds to the way all 3D engines basically work. SVG on the other side is designed as a 2D description format. It knows more shapes than only triangles - what makes sense and is efficient if you are in 2D space. In theory you can always assemble any polygon out of triangles. This is what is done at the very low level end in all renderers I guess (OpenGL at least does so).
Now, the problem is, all popular SVG renderer today try to be "nice looking". I.e. they render edges antialiased. Antialiasing involves transparency. And transparency involves a change of color. If you try to draw adjacent edges antialiased you end up with the result you obtain: The color on the edge will vary slightly, leaving an imaginary line where a solid colored area is expected.
This is an limitation of SVG - not of ILNumerics. If you want to use SVG in order to create solid filled polygon shapes, you need to 'design' by using those shapes provided by SVG. If you observe different results in SVG files created by other libs, post these SVG as an example here in order for us to inspect them. I am pretty sure they will not use triangles. (?)