Bug. Mismatch between image plugin .obj and .png co-ordinate systems

[mbarrow]

I have run into weird behavior in the flexible app and Image plugin.
It seems there is some slight mismatch between the coordinate systems. I’m not sure how to remedy the situation.

I have a beam simulation where I want to map an ogl model to a mechanical object for display. The ogl model has a slight y and z offset that I did not specify. I can’t account for it and it will mess up some calculations I’d like to do down the road.

I’ve applied what I believe to be correct transforms to a .png when creating the mechanical object.

Can someone explain how to account for this offset or why it occurs at all?

I’ve attached a .scn that shows the issue. the .scn can be run in “src/applications/plugins/Flexible/examples/beam/” but it needs a 100×500 pix png called “beamr.png” that I couldn’t attach.

It also demonstrates a rendering bug of the image plugin in the “beamimage” node. This node does not render the beamr.png unless a redundant offset of one extra pixel is added to the dx parameter of that node. That shouldn’t be at all.

 <?xml version="1.0"?>
<Node 	name="Root" gravity="0 0 0 " dt="1"  >
    <RequiredPlugin pluginName="Flexible"/>
    <RequiredPlugin pluginName="image"/>
    <VisualStyle displayFlags="showWireframe showBehaviorModels" />
    <DefaultAnimationLoop />
    <DefaultVisualManagerLoop />

	<!-- just highlights the expected y and z for an obj loader. I added the x offset to make the other stuff easier to see -->
    <Node 	name="objCoOrds"   >
	<VisualStyle displayFlags="hideWireframe" />
        <OglModel template="ExtVec3f" name="Visual" fileMesh="beam.obj" color="0.5 0.5 0.5" translation="-1 0 0" rotation="90 0 0 "/>
    </Node>

	<Node name="Affine"   >
		<VisualStyle displayFlags="showWireframe" />
		
		<EulerImplicitSolver  rayleighStiffness="0.1" rayleighMass="0.1" />
		<CGLinearSolver iterations="200" tolerance="1e-15" threshold="1e-15"/>
		
		<ImageContainer name="loader" filename="beamr.png" drawBB="false" />
		<ImageFilter name="selectchannel" src="@loader" filter="21" param="0"/>
<!-- hand tuned parameters that do work. it is unacceptable to hand tune these y and z offsets. -->		
<!--  		<ImageFilter name="pngCoOrds" inputImage="@selectchannel.outputImage" filter="20" param="-0.20 -0.998 -0.16 100.00 500.00 5.0 0.0040 0.0040 0.08 0" inputTransform="-0.20 -1.00 0 00.00 0.00 0.00 0.0040 0.0040 1.0 0 1 0"/> -->
<!-- parameters one would expect to work but dont because of bizarre offsets issue. note that image viewer doesn't work unless width is 101 but the actual values appear to be sampled correctly never the less. -->
<ImageFilter name="pngCoOrds" inputImage="@selectchannel.outputImage" filter="20" param="-0.20 -1.00 -0.2 100.00 500.00 5.0 0.0040 0.0040 0.08 0" inputTransform="-0.20 -1.00 0 00.00 0.00 0.00 0.0040 0.0040 1.0 0 1 0"/>
	    <ImageContainer name="beamimage" image="@pngCoOrds.outputImage" transform="@pngCoOrds.outputTransform" drawBB="false"/>
		<TransferFunction name="youngMTF" template="ImageUC,ImageD" inputImage="@pngCoOrds.outputImage" param="0 0 1 7.843 255 2000.000"/>
		<ImageViewer template="ImageD" name="modulusviewer" image="@youngMTF.outputImage" transform="@pngCoOrds.outputTransform" display="1"/>

		<MeshObjLoader name="mesh" filename="beam.obj" triangulate="1" rotation="90 0 0 "/>
		<ImageContainer template="ImageUC" name="image" image="@pngCoOrds.outputImage" transform="@pngCoOrds.outputTransform" drawBB="true"/>

	    <ImageSampler template="ImageUC" name="sampler" src="@image" method="1" param="0" fixedPosition="0 -1 0   0 -0.8 0   0 -0.6 0  0 -0.4 0   0 -0.2 0   0 0 0    0 0.2 0   0 0.4 0  0 0.6 0  0 0.8 0  0 1 0" printLog="false"/>
		<MergeMeshes name="merged" nbMeshes="2" position1="@sampler.fixedPosition"  position2="@sampler.position" />
		<MechanicalObject template="Affine" name="parent"  showObject="true" src="@merged" />
		
		<Mesh name="edges" position="@parent.rest_position" edges="0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10"/> 
   		<BarycentricShapeFunction  position="@parent.rest_position" nbRef="2" />
		<ShapeFunctionDiscretizer name="SF" src="@image" />

	    <Node name="behavior"   >
			<ImageGaussPointSampler name="sampler" indices="@../SF.indices" weights="@../SF.weights" transform="@../SF.transform" method="2" order="4" targetNumber="1"/>
			<MechanicalObject template="F332" name="F"  />
			<LinearMapping template="Affine,F332"  />
		</Node>

		<Node 	name="visual"   >
		    <OglModel template="ExtVec3f" name="Visual" fileMesh="beam.obj" color="1 0.8 0.8" rotation="90 0 0"/>
			<LinearMapping template="Affine,ExtVec3f"/>
		</Node>
	</Node>
	
</Node>

[Hugo]

Dear @mjbarrow,

Could you find a way to provide us a link (wetransfer or any other) of your image?
This would really ease the testing.

Did you take a look at the BeamLinearMapping component?

Best,

Hugo

[mbarrow]

sure, here is a 100×500 white beam png image

thanks for the suggestions I will try them. This link is also good for my other question which is actually quite a lot more pressing for me if you could take a look?

its here: how to use node output as “param” for ImageFilter?

Thanks very much for responding to my questions

[Hugo]

Hi @mjbarrow

Are you still struggling with the orientations?
Best

Hugo

[mbarrow]

Yes I don’t understand that component. I saw it used in beamFEMForceField.scn but I was not successful when I placed it in the same node as the RegularGridTopology that is used for the FEM forcefield. I can keep trying but just giving an update since you ask

[Author]

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