H3D.org - Forum

Re: Rendering a surface with some thickness

Fri, 10 Sep 2010 06:52:02 -0500

That is great. If you ever need to make it faster maybe you can use geometry shaders to do the thickness instead of generating a new IndexedTriangleSet.

Re: alpha blending

Fri, 10 Sep 2010 06:32:20 -0500

No, I don't think that the functionality required for that is available in VHTK, or in MedX3D for that matter. To render two volumes at the same place with individual renderers would require the renderers to interleave their individual slices, which is not possible with the current implementation.

One alternative would be to render the two volumes onto frame buffer objects that can then be combined into one image. That will not, however, give the correct impression of depth.

Another alternative would be to combine the two volumes into one volume in a way so that they can be discriminated in the rendering using a special set of transfer functions.

Finding the intersection line between two polygons

Wed, 8 Sep 2010 07:40:39 -0500

Suppose, I have two polygons, one consisting of a number of triangles and another a number of quads. How to find the intersecting line between the polygons. Here one quad can with a number of triangles or one triangle can intersect a number of quads.
Any suggestion will be highly appreciated.

Re: VTK anf H3d API

Wed, 8 Sep 2010 01:14:30 -0500

I know it is possible. I am sure there are some users in the forum that have done it (no idea who though, try to search for vtk in the forum search feature). If you do not find any good example you can test a bit on your own.

Re: Composed volumes

Mon, 6 Sep 2010 07:56:27 -0500

Quote:

does the the pixel_data + bytepercomponent statement that you give to writeFloatasRational behave as you sexpect it to?

This brings me to another question. How should color (RGBA) be set? That is, should RGBA be 0x0000ff00 or R= 0.00 (float 32 bits), G = 0.00 , B = 1.00 and A = 0.00 ?

Anyway, I found a way of getting VolumeRenderer (in VHTK) render my composed volume in color using a color map.

Thank you very much for your help, Markus. Really, you're superb in these H3DAPI stuffs.

Re: Falcon shivers

Thu, 2 Sep 2010 01:56:26 -0500

Since you are using a couple of thousand triangles in the haptic loop (which might or might not be at the limit of how many it can handle at 1kHz, depends on your computer) I suggest that you use the HAPIHapticsDevice::getHapticsRate() function to log/print the actual haptics rate once or twice every second. If you frequently get values below 950 then you should try reducing the amount of triangles sent to the haptics loop.

It is always possible to scale the scene. Ogre is OpenGL right? Which means that you should be able to enclose your scene in a way similar to this:

renderStylus()
glPushMatrix()
glScalef( 0.001, 0.001, 0.001 )
renderScene
glPopMatrix()

If you use the FeedBackBufferCollector just make sure that the same scale is applied before rendering the triangles and they should be in the same coordinate system as the haptics device. Roughly outlined.

I really can not say if it is the scaling problem, but if I use H3DAPI and set a huge scale (300 or so) for the positionCalibrationMatrix of the haptics device then weird things can happen on a single cube. It depends a bit on how I move the device. If I am really careful everything might work fine. Since we are not sure about where the problem is I would suggest starting to check the haptic framerate then if that seems ok try to make a quick-hack to scale your world and not the position calibration, just to test.

Re: HAPI-1.1.1 compile error with linux, gcc 4.5.0

Thu, 2 Sep 2010 01:28:52 -0500

Did you check if they are fixed in HAPI/trunk?

alpha blending

Thu, 2 Sep 2010 01:01:04 -0500

Hi Karlu,

I have two volumes of MRI data. I managed to have one volume (processed data) displayed as a color volume using the RGBFunction for VolumeRenderer. Now I need to blend the color volume on top of a gray-scale volume (to reveal the anatomy).

Is there any node/function in VHTK which will do this?

I can sort of having this done by messing around with the RGBFunction again but it is a requirement of the project to have the alpha blending adjustable on the flight. I have very limited experience with OpenGL. I have been studied VHTK and your papers/thesis so I know VHTK better.

thank you for your guidance,

Trang

Re: Rendering a surface with some thickness

Wed, 1 Sep 2010 19:39:19 -0500

I've got something working now, but I didn't do anything in the render() function. I created a new Node (ThickMembrane) inherited from DeformableShape, but kept the DeformableShape attribuets hidden. Instead my new Node has its own coord and index fields, as well as a thickness. It then internally builds an IndexedTriangleSet as an 'envelope' around the provided coords with the given thickness and sets it as the DeformableShape's geometry. The haptic geometry is just made up of another internally created IndexedTriangleSet using just the original coords. So you provide the coords of a single surface, get that for your haptics, but a thicker version, with enclosed edges, for your graphic representation. The membrane can also have holes in it. I have submitted it to the Nodes download section.

2 Master Thesis projects in Stockholm, Sweden

Wed, 1 Sep 2010 01:51:41 -0500

Unfortunately these offerings are only in Swedish but I did a Google translate:

first one, and second one!

/Johan

Rendering a surface with some thickness

Tue, 31 Aug 2010 19:35:13 -0500

I would like to graphically render a DeformableShape containing an IndexedTriangleSet with some thickness. So essentially the problem is that an IndexedTriangleSet is rendered as a very thin sheet. I would like to specify it like that but when it is rendered it should have a small thickness. Haptically, it could behave as the default IndexedTriangleSet, as the thickness would be unnoticable, but graphically it needs to be seen to have a finite thickness, typically about 0.002.
Of course I could always construct the full set of triangles to do this, but I was wondering if there any way to get the render() function to do this internally? Any advice on how to do this?

VTK anf H3d API

Tue, 31 Aug 2010 13:14:48 -0500

Do you know if is possible use VTK and H3DAPI in the same code? an example that I could provide? I just need an object, either in VTK and to use the haptic tool for intaractuar, thanks ...

Re: Falcon shivers

Mon, 30 Aug 2010 11:23:18 -0500

Thanks for the information.

For the triangles, I am sending a couple of thousand..
I have to find a work around the frame rate problem.
For the moment my concern is the unexplained bouncing.

Regarding the scaling part,if that might be the cause, this is my code where I calibrate the position of the proxy to be aligned with the camera:
http://www.h3dapi.org/modules/newbb/viewtopic.php?topic_id=1142&forum=4 (last post)

the WORLD_SCALE value is set to 300.
I am not sure I can 'scale the scene'. I use a rendering engine which is unitless, I decide what 1 unit will translate to so it all works in analogies.
If I remove the WORLD_SCALE multiplication then the proxy moves so slightly that it is almost still.

What bothers me though is that if the scaling is the problem, why does it work alright for simple solids like cubes and spheres but when I import models that consist of 8-10 such objects the bouncing starts?

Thanks in advance..

HAPI-1.1.1 compile error with linux, gcc 4.5.0

Fri, 27 Aug 2010 14:42:46 -0500

Compiling with

gcc (SUSE Linux) 4.5.0 20100604 [gcc-4_5-branch revision 160292

I get the following compile errors. Anyway they are easy to fix.

HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d(const H3DUtil::ArithmeticTypes::Quaterniond&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:120:61: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:120:61: error: for a function-style cast, remove the redundant ‘::Matrix3d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d(const H3DUtil::ArithmeticTypes::Quaternion&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:125:50: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:125:50: error: for a function-style cast, remove the redundant ‘::Matrix3d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d(const H3DUtil::ArithmeticTypes::Rotation&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:129:48: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix3d::Matrix3d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix3d.cpp:129:48: error: for a function-style cast, remove the redundant ‘::Matrix3d’

HAPI-1.1.1-Source/H3DUtil/src/Matrix3f.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix3f::Matrix3f(const H3DUtil::ArithmeticTypes::Quaternion&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix3f.cpp:120:61: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix3f::Matrix3f’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix3f.cpp:120:61: error: for a function-style cast, remove the redundant ‘::Matrix3f’

HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d(const H3DUtil::ArithmeticTypes::Rotationd&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:53:16: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:53:16: error: for a function-style cast, remove the redundant ‘::Matrix4d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d(const H3DUtil::ArithmeticTypes::Quaternion&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:57:50: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:57:50: error: for a function-style cast, remove the redundant ‘::Matrix4d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d(const H3DUtil::ArithmeticTypes::Rotation&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:61:48: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:61:48: error: for a function-style cast, remove the redundant ‘::Matrix4d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d(const H3DUtil::ArithmeticTypes::Quaterniond&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:82:42: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:82:42: error: for a function-style cast, remove the redundant ‘::Matrix4d’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d(const H3DUtil::ArithmeticTypes::Matrix3d&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:91:42: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4d::Matrix4d’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4d.cpp:91:42: error: for a function-style cast, remove the redundant ‘::Matrix4d’

HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f(const H3DUtil::ArithmeticTypes::Rotation&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:53:16: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:53:16: error: for a function-style cast, remove the redundant ‘::Matrix4f’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f(const H3DUtil::ArithmeticTypes::Quaternion&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:74:42: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:74:42: error: for a function-style cast, remove the redundant ‘::Matrix4f’
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f(const H3DUtil::ArithmeticTypes::Matrix3f&)’:
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:83:42: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Matrix4f::Matrix4f’ directly
HAPI-1.1.1-Source/H3DUtil/src/Matrix4f.cpp:83:42: error: for a function-style cast, remove the redundant ‘::Matrix4f’

HAPI-1.1.1-Source/H3DUtil/src/Quaternion.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Quaternion::Quaternion(const H3DUtil::ArithmeticTypes::Matrix3d&)’:
HAPI-1.1.1-Source/H3DUtil/src/Quaternion.cpp:97:42: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Quaternion::Quaternion’ directly
HAPI-1.1.1-Source/H3DUtil/src/Quaternion.cpp:97:42: error: for a function-style cast, remove the redundant ‘::Quaternion’

HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Rotation::Rotation(const H3DUtil::ArithmeticTypes::Matrix3f&)’:
HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp:75:33: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Rotation::Rotation’ directly
HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp:75:33: error: for a function-style cast, remove the redundant ‘::Rotation’
HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Rotation::Rotation(const H3DUtil::ArithmeticTypes::Matrix3d&)’:
HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp:81:33: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Rotation::Rotation’ directly
HAPI-1.1.1-Source/H3DUtil/src/Rotation.cpp:81:33: error: for a function-style cast, remove the redundant ‘::Rotation’

HAPI-1.1.1-Source/H3DUtil/src/Rotationd.cpp: In constructor ‘H3DUtil::ArithmeticTypes::Rotationd::Rotationd(const H3DUtil::ArithmeticTypes::Matrix3d&)’:
HAPI-1.1.1-Source/H3DUtil/src/Rotationd.cpp:66:35: error: cannot call constructor ‘H3DUtil::ArithmeticTypes::Rotationd::Rotationd’ directly
HAPI-1.1.1-Source/H3DUtil/src/Rotationd.cpp:66:35: error: for a function-style cast, remove the redundant ‘::Rotationd’

Re: Falcon shivers

Fri, 27 Aug 2010 01:54:42 -0500

It could be the scaling value, if it is very big. What is your positionCalibration matrix? Please try to scale the scene instead of the positionCalibration matrix. If you scale the scene to fit in a box with around 0.2 * 0.2 m and give a unity matrix as positionCalibration matrix, just to test.

How many triangles are you sending to the haptic loop? If you have to many triangles in the haptic scene then the haptic rendering might not update at 1kHz which will give you problems. In H3DAPI this is taken care of by only sending triangles within a specific radius from the haptics device at any time. The radius is decided by factors such as the speed of the haptics proxy (how fast the user is moving) and some user multiplication values. So in a scene with 1 million triangles there should only be a few hundred in the haptic loop at one time. Every frame the haptic triangles are changed.

Re: Falcon shivers

Tue, 24 Aug 2010 14:25:12 -0500

Hi Markus,
Thanks for your reply.

I am adding the triangles since I use HAPI.I only rotate and move the model.

Without being 100% sure, I think the issue with some polygons of the model being felt while others not has to do with the setting of the model in Maya. It seems that some triangles were not recognised when the polygons were 'combined' together. Some models work, some not. I am trying to track this down with tests.

Still though, Falcon bounces on every part it touches even with correct set parameters for the Frictional Surface. It does work fine with simple primitives though (cube, sphere, torus etc all exported from Maya). I checked the maths behind the set of the parameters -following the HAPI manual- and everything I set should have worked well.

Re the scale, I have a position & orientation calibration matrix and I scale the workspace of the device so that it works ok with the rendering environemnt (graphical one) as there is big difference between them in terms of units. If I don't scale it, the proxy representation moves only in a very small region box. So small one might think it doesn't move at all.Do you think this might cause a problem?

Further, I am concerned a bit about the frame rate. Obviously, the Release mode is quicker that Debug but still overall the rendering, even without any transformations taking place, is really slow. I was wondering if the Callback function is needed to track changes in the graphic rendering. So far, I hold the changes in a boolean and I re-draw the haptic triangles every time there has been a change in the model. (perhaps this should go into a new post)

Thanks in advance..

Re: Falcon shivers

Tue, 24 Aug 2010 08:05:12 -0500

Did you add the spheres haptically as triangles or as the sphere primitive? It is better to use the latter approach. Are they working properly or are you bouncing when you touch them?

Again, do you have some weird transforms or only translations and simple rotations?

Did you check that the triangles are collected properly for the box object? If they are not then you will not feel anything.

Did you set some kind of position calibration matrix that scales the haptic workspace a lot? If you did then that might be your problem.

Re: Error in Scene destruction.

Tue, 24 Aug 2010 07:56:28 -0500

To me it looks like unref is done on a Node which is already deleted from the scene. Did you call delete on some node without it being removed from the scene graph?
If I could hazard a guess it looks like it is the window that is contained in Scene::window that is deleted without being unrefed. Are you doing some external deletion on nodes?

That is, nothing is locked, the lock does not exist because its parent does not exist.

Re: Composed volumes

Tue, 24 Aug 2010 07:46:16 -0500

Are you sure you are writing to the correct place in the target variable?
Not entirely sure but to me it looks like you are overwriting the same block of data over and over again.

That is at target[0] you write four floats.
Then at target[1] you write four floats, overwriting three of the previous four floats.... Not entirely sure about this.

Also, does the the pixel_data + bytepercomponent statement that you give to writeFloatasRational behave as you sexpect it to?

Re: image->getValue()

Tue, 24 Aug 2010 06:59:23 -0500

getImageData returns a pointer to the raw image data. How the data is structured in memory, or rather how to access individual values is decided by the pixelType, pixelComponentType and bitsPerPixel functions. If you are interested in modifying the data directly you should probably take a look in Image.cpp and try to figure out how it works.