Geometrian

Hi,

I had come across an . . . unusual programming situation.

I have a FBO2D base class, which implements a 2D framebuffer object, and I wanted to implement a FBOCube class derived from it, implementing a cubemap framebuffer object. The point is that FBOCube is essentially six FBO2D classes, but it still kinda makes sense to derive from it. In effect, I want six FBO2D parents for a single object. The language is C++.

I realize this is awful, and I'm redesigning it, but I thought it was an interesting thing. I'm pretty sure it's not possible in C++. I'm curious: what does the programming community think?

-G

Hi,

I have a bizarre problem. There is a simple OpenGL fixed-function light drawn at (0.0f,10.0f,-1.0f). There are several boxes that happen to have faces lying in the plane z=-1.0f. Consequently, the light vector and the normal are exactly orthogonal.

When this happens, instead of being black, the color flickers light and dark along that face, even when the camera is stationary. The draw settings are identical each frame. It's not a z-fighting effect; there's only one layer of polygons, and the flickering continues even when the camera is stationary. Each vertex of the face appears either lit or unlit, though it's unpredictable which a given vertex will be from frame to frame.

The light has no ambient, and by tweaking the light's diffuse and specular factors, I find that the problem only occurs when the light's specular coefficient is nonzero. Perturbing the light slightly along z fixes the problem; it's only when the light is exactly in line with the surface that the problem occurs. I can fix the problem better by just using a shader (which I plan to do anyway), but I'm wondering if anyone has encountered this before?

I suspect it may be some kind of driver bug.

Hardware: NVIDIA GeForce GTX 580M

Driver: 305.60

Thanks,

-G

Hi,
 
I can create a Bullet heightmap and collide with it. The results generally seem to be correct (large scale features are there). To test, I drop some objects in random places and have a look.
 
A perfectly flat heightmap is collided perfectly (of any height, as long as it's constant).
 
However, if the heightfield is sloped, objects penetrate a surprisingly far distance (seemingly related to the slope at that point).
 
For completeness, how the heightfield is made:

float scale[3] = {1.0f,1.0f,1.0f};
 
//create and fill data
 
btHeightfieldTerrainShape* new_shape = new btHeightfieldTerrainShape(data_size[0],data_size[1], data, 1.0f, 0.0f,scale[1], 1, PHY_FLOAT, true);
new_shape->setLocalScaling(btVector3(scale[0],1.0f,scale[2]));

offset[0] = scale[0]*data_size[0] * 0.5f;
offset[1] = scale[1]              * 0.5f;
offset[2] = scale[2]*data_size[1] * 0.5f;
 
//translate heightmap's associated body to "offset", thus
//putting one corner of the heightmap at the origin.

Here's a screenshot from underneath a heightmap of some cubes falling on it. Notice that the cubes penetrate about 10% to 20% of their depth in!

Thanks,

-G

int version[2];
glGetIntegerv(GL_MAJOR_VERSION, version );
glGetIntegerv(GL_MINOR_VERSION, version+1);
printf("OpenGL %d.%d\n",version[0],version[1]);

Hi,

I'm looking for a way to animate humanoid characters in a physically-based manner. This is a problem of Physics and AI, but I think it's more a problem of AI. I asked about it on BulletPhysics.org here, but didn't get any answers. The problem is: given a ragdoll character, make it, under its own force, move around.

I have looked around a bit, but wasn't able to find anything useful in the way of a toolkit--mostly it's just technical papers on the topic.

My requirement is that the character is able to walk or run in any direction over fairly varied terrain, and get up after a fall. Pose matching, within reason, is also necessary. Minor attempts to correct if an obstacle has been tripped over would be nice. Open source is a must.

Having read a bit of the literature, I realize that these aren't trivial requirements, but there are for example youtube videos that demonstrate the technology in action. The problem is, there aren't toolkits that do it, as far as I can tell.

Thanks,