# Issue when porting an example sketch from the Hemesh library to Python mode

**URL:** <https://discourse.processing.org/t/issue-when-porting-an-example-sketch-from-the-hemesh-library-to-python-mode/8570>\
**Category:** Processing.py\
**Created:** [February 20, 2019, 5:25pm UTC](https://discourse.processing.org/t/issue-when-porting-an-example-sketch-from-the-hemesh-library-to-python-mode/8570 "2019-02-20T17:25:50Z")\
**Posts on this page:** 1\
**Showing post:** 6

<div class="post-metadata">

**Author:** ![GoToLoop](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/gotoloop/32/86_2.png) [@GoToLoop](https://discourse.processing.org/u/GoToLoop)\
**Post date:** [February 22, 2019, 12:35am UTC](https://discourse.processing.org/t/issue-when-porting-an-example-sketch-from-the-hemesh-library-to-python-mode/8570/6 "2019-02-22T00:35:10Z")

</div>

WB\_Render3D::**drawTriangle()** got 6 overloaded versions of it:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3475-L3553>

And outta those 6, there are 2 w/ the 1 parameter signature that is a container:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3475-L3476>

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3500-L3500>

And 1 w/ 1 parameter that is a single WB\_Triangle:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3547-L3547>

Method WB\_IsoSurface::**getTriangles()** returns a List\<WB\_Triangle\>:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/geom/wblut/geom/WB_IsoSurface.java#L405-L421>

But if we call `print type(triangles)`, we’ll find out its actual datatype is:  
`<type 'org.eclipse.collections.impl.list.mutable.FastList'>`

[Eclipse.org/collections/javadoc/9.0.0/org/eclipse/collections/impl/list/mutable/FastList.html](http://Eclipse.org/collections/javadoc/9.0.0/org/eclipse/collections/impl/list/mutable/FastList.html)

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/geom/wblut/geom/WB_IsoSurface.java#L154-L154>

Now it seems like when we invoke `render.drawTriangle(triangles)`, the overloaded signature chosen is:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3500-L3500>

Which causes `processing.app.SketchException: java.lang.ClassCastException: wblut.geom.WB_Triangle cannot be cast to wblut.geom.WB_Coord`

But what we’re looking for is this 1:

> <https://github.com/wblut/HE_Mesh/blob/4d7c02a9775429c8f7c1872194b8a7aadd038f08/src/processing/wblut/processing/WB_Render3D.java#L3475-L3476>

I’ve tried searching for some Jython builtin way to force a method invocation to pick a specific signature.

However, if there’s 1, it’s unpublished or it’s almost impossible to find!  
As a workaround, I’ve attempted Java’s reflection capabilities.

1. Class::**getMethod()**:  
[Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Class.html#getMethod(java.lang.String,java.lang.Class...)](http://Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Class.html#getMethod(java.lang.String,java.lang.Class...))
2. Method::**invoke()**:  
[Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/reflect/Method.html#invoke(java.lang.Object,java.lang.Object...)](http://Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/reflect/Method.html#invoke(java.lang.Object,java.lang.Object...))

There’s a subtle diff. between the container parameter type signatures.  
The 1 for WB\_Coord is a List, but the 1 for WB\_Triangle is a Collection.

So in order to grab the overloaded method signature we need we do like this:  
`method = WB_Render.getMethod('drawTriangle', Collection)`

Now, inside **draw()**, we replace `render.drawTriangle(triangles)` w/ `method.invoke(render, triangles)`.

Here’s the full sketch solution: 👼

```auto
"""
 Ref_WB_IsoSurface (v1.0.1)
 ported by GoToLoop (2019-Feb-21)

 https://Discourse.Processing.org/t/
 issue-when-porting-an-example-sketch-from-the-
 hemesh-library-to-python-mode/8570/6
 
 https://GitHub.com/wblut/HE_Mesh/blob/master/examples/
 geom/isosurface/Ref_WB_IsoSurface/Ref_WB_IsoSurface.pde
"""

add_library('hemesh')

from java.util import Collection
METHOD = WB_Render.getMethod('drawTriangle', Collection)

DIM, N = 51, .07
DRANGE = tuple(range(DIM))

BG, FG, FILL = 070, 0, -1
FPS = 'FPS: '

def setup():
    size(800, 700, P3D)
    smooth(8)

    fill(FILL)
    stroke(FG)

    creator = WB_IsoSurface()

    creator.setSize(8, 8, 8)
    creator.isolevel = .6
    creator.boundary = -200
    creator.gamma = .3
    creator.invert = False

    creator.setValues(
        [[[noise(N*x, N*y, N*z) for z in DRANGE]
        for y in DRANGE] for x in DRANGE]
    )

    global render, triangles
    render, triangles = WB_Render(this), creator.triangles

def draw():
    background(BG)
    lights()

    translate(width>>1, height>>1)
    rotateY(TAU * mouseX / width)
    rotateX(TAU * mouseY / height)

    # render.drawTriangle(triangles) # invokes wrong sig!
    METHOD.invoke(render, triangles)

    this.surface.title = FPS + `this.round(frameRate)`

```

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