Is there a software that can only render part of a mesh? - mesh

Is there such a software that can render only part of a mesh, while rendering the whole surface, as shown in the following picture? It will be perfect if it works for triangular mesh. Any help will be appreciated!
https://www.dropbox.com/s/pqpp0ijrmkm4fiv/nPower-SubD-NURBS-old-man-e1297714632154.jpg

Related

Render horizon silhouette using Metal in SceneKit

I'm working on simple side project and small part of it is rendering a terrain. I'm rendering the terrain using height map information. But here is my problem:
I would like to render just a silhouette/outline of the terrain/horizon. Here is screenshot from my app rendering height map:
And here is screenshot similar to desired result from peakfinder.org:
I would like to draw just lines representing silhouette of terrain with the rest transparent or solid colour. How can I solve it? Calculate local maximum somehow?
I created sample project here, in case you want to help me.
Thanks!

problems with CGAL AABB tree

I am using CGAL's AABB tree to perform point-location queries for my project. I have a cartesian grid in 3D and a surface immersed inside the grid. I need to find which elements of the grid are outside/inside/cut by the surface. For this, I cast a Ray and find the number of intersections for each corner of the cell and check if they are inside or outside.
This works fine as long as the corners of the grid do not coincide with nodes on the surface. But, I get rubbish results when the corner points of the cell coincide with nodes on the surface. One such scenario is shown in Erroneous result from CGAL.
I tried using Simple_cartesian<double> and Exact_predicates_inexact_constructions_kernel but the situation did not improve.
It seems that CGAL is so sensitive to floating point operations.
How can solve this issue?
Without seeing the code you wrote it is hard to say where the problem is. However the class Side_of_triangle_mesh seems to be exactly what you need.

Render texture and normalized view rect in Unity

I'm using Unity 3D 3.5 pro.
I've got this scene with two cameras in it. One of them is looking at a plane that has a render texture on it. The other is recording the render texture. When the camera that's recording the render texture has a 1:1 normalized view and height rect, everything is fine. But when It's something different, some weird stuff happens -- the render texture's image becomes distorted. I've tried releasing and discarding the render texture's contents in an update function, but nothing changes! It's totally stopping the project I'm working on from being completed. I have pictures here to explain the situation in detail. The reason its a problem is because i need to be able to place non rectangular objects in front of the square and not have their scales appear to be distorted, due to the scale of the plane on which the render texture is being shown not being a square. What could I be doing wrong?
I also placed a similar question on unity answers, but received no usable help there. Here was the thread:
http://answers.unity3d.com/questions/389094/rendertexture-normalized-view-rect.html
I figured it out. I needed to mess with the offset and tiling of the rendertexture. Silly rabbit!

blender export / one sided polygons

I'm really new to 3d modeling, blender, etc.
I created a model with blender (a room). Now I exported it (as .obj) so that I can import it to CopperCube (a tool to create 3d scences).
The problem is, that the walls are only visible from outside. Take a look into the pictures:
Blender:
http://imageshack.us/photo/my-images/341/blenderg.png/
CopperCube:
http://imageshack.us/photo/my-images/829/coppercube.png/
I asked the forum of CopperCube and they said that there are only one-side polygons (or flipped). Is there a way to change this? Sorry, but I am a total beginner with this...
Here's the answer of the CopperCube forum:
I don't know blender, but are there any options you can change for exporting? It looks like your model just has one sided polygons, or the normals are flipped for some of them.
Make sure you have the normals checkbox checked in OBJ export options (at the left side, it's off by default):
You will need to model your room to have slim cubes instead of planes whenever they should be visible from both sides.
You can display the normals in Blender in edit mode. In Properties (N) scroll down to Mesh Display and check the type of normals you want to see and their length.
To recalculate the normals or flip their direction go to the Tool Shelf (T) in the Normals section.

Refraction for object { mesh {...}} surface shows artifacts

We want to render a parametrized surface in front of a grid plane and observe the transformation of the grid due to refraction happening at the surface. Our surface is in this simple example a 2D normal distribution which we will view directly from above and the grid plane is placed below:
The surface is given in many triangle directives which we put together in a mesh and used it with
object {
fovea
scale <1,1,3>
texture { pigment {color rgbt <0,0,1,0.5> }}
interior {ior 1.4}
}
The scale here is not necessary and used only to amplify the artifacts. What you see in the image below is, that the refraction seems not to happen smoothly, but creates some sharp artifacts in the underlying grid pattern.
This image was created with Povray 3.6.1 under MacOS X 10.5.6 with the settings +Q9, +A and -J. Can anyone point out a hint? Thanks.
This was a stupid mistake. Since in Mathematica the surface looked really smooth, I assumed that it created a large number of triangle-faces. This assumption was wrong. The rendering engine Mathematica uses, seems to interpolate the normals given for each vertex and therefore the surfaces only looks as it has a high resolution.
A check of the underlying polygons reveals the truth:
Therefore, what looks like refraction artifacts in the rendered image above is actually correct behavior, because the face-normals of neighboring triangles really change that much.
Increasing the resolution of the surface grid solves the problem.