Questions tagged [3d]

Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.

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68 views

3D sphere mesh with a predefined number of vertices and a given adjacency matrix of vertices

I need a 3D triangular sphere mesh with uniformly sampled vertices, say $V$, with a predefined adjacency. Is there a specific way to achieve that?
4
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1answer
733 views

Rotation matrix for a 3D object in space

This is the follow-up question from here: Minimum requirements to uniquely represent a 3D object in space Assume I have 3 original points in a 3D object (in 3D space) as ...
6
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1answer
185 views

3D projection that increases objects' size as they become more distant

tl;dr Is there a name for a type of (non-physical) projection that causes objects to become larger the farther they are from a camera? With a fisheye projection, an object twice as far from the ...
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0answers
160 views

Interpolation of orientations

I have a problem of linear interpolation of CRV (Conformal Rotation Vector) in which CRVs are used to parameterize the orientations. In my knowledge, in order to derive a linear interpolation of ...
5
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1answer
89 views

Best way to group 3d points into planes, if any

If I have some 3d points, how can I discover parallel planes within them (not just arbitrary planes). I want to know how many "levels" or "floors" something can travel within, after it has done so, ...
5
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2answers
217 views

What is missing in this image that stops it from looking like a photograph?

Look at this image: This is CG, Saya, a project meant to make as real CG as possible to the point of becoming indistinguishable from reality. I would say that it is pretty believable. But, it still ...
11
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1answer
697 views

Is this the correct way to implement Beer's Law?

When I implement Beer's law (color absorption over distance through an object), it never looks very good for some reason. When i have the color behind the object, I calculate the adjusted color like ...
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1answer
4k views

How to make a 3D model for Unity 5 [closed]

I'm using Unity 5 to make a small game (I'm a beginner) and I want to make a 3D model of a character. I'm not sure what software there is to do this and if there is some, I would like it to be ...
1
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1answer
483 views

How do I implement object picking, using OBB in OpenGL?

I am trying to make 3D drawing software. I wanted to have the drag feature so I am using object picking using the OBB algorithm. I am facing problems in understanding the algorithm, and my ...
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0answers
86 views

Advice on synthetic data generation using 3D mesh

I'm developing a deep learning algorithm to find and classify (post consumption) plastic bottles on a conveyor belt. A way to train my model is to get tons of labeled images of each bottle, which for ...
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0answers
348 views

Tilting a 3d object to face a camera and have it look like it's spinning on the y axis

I have a scene kit app I'm working on and at a certain point I move the camera under a list of objects and tilt it up to give a star wars type view of them. I then need to pull the objects up one at a ...
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1answer
85 views

Which 3D object properties should be affected by distance?

Which 3D object properties should be affected by distance in VR and other 3D applications and how important is it that they are changed? For example the level of detail, colour (?)...
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1answer
57 views

What metrics are used for deciding if a 3D object is visible?

I'm wondering what metrics I could use to decide upon the visibility of a 3D object in VR or other 3D applications and what advantages each has.
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1answer
335 views

Beginner CG Research Project [closed]

This summer I will be working with a professor on a research topic of my choice, in the field of graphics & simulation. While my professor is knowledgeable in the area he is being very hands off ...
4
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1answer
1k views

Bevel/Chamfer algorithm for arbitrary 3D mesh

I can't find any paper about a bevel/chamfer algorithm for 3D mesh. Bevel has a lot of special cases (corners, different bevel profile, bevel larger than a face). I am looking for robustness. Do you ...
3
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0answers
241 views

How to output a 32 floating value in a render buffer with fragment shader

I would like to downsample my depth buffer and my normals. For that, I take in input of my shader, the corresponding textures (depth, normal), and I write my new values in a multi render target. I ...
7
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2answers
913 views

How to translate mouse movement to a rotation gizmo?

I need to implement translation, scaling and rotation gizmos and I'm having trouble with the rotation gizmo. Basically I don't know how to translate the mouse movement to determine in which direction ...
3
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1answer
604 views

How to properly direct light sample GGX in path tracing

I have been trying to implement the GGX shader in my path tracer based on this paper: Microfacet Models for Refraction through Rough Surfaces It's pretty clear how the importance sampling works, but I ...
6
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1answer
254 views

Mix shader looks wrong on my path tracer

I apologize if my methods seem way off because this is my first time trying to build a path tracer and I'm struggling quite a bit. Currently, I am trying to mimic the "mix shader" node in Blender 3D ...
4
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1answer
132 views

How does a rigged model work?

What black magic is behind this? Starting from a pile of polygons, a skeleton, and an initial conformation, how is a new conformation turned into a new pile of polygons?
5
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2answers
1k views

Is there a way to draw spherical objects without triangles?

It seems that in all existing graphics libraries, 3D objects are always described in terms of triangles. Drawing triangles can be implemented very efficiently on video hardware and since any 3D object ...
4
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2answers
184 views

File format for swept profile with changing normal

I have to create a file describing a 3d surface with the following properties: a circular arc cross section is swept along a closed 2d curve spine defined with equations the normal direction of the ...
7
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2answers
7k views

How to achieve gimbal lock with Euler angles?

I was studying about Euler angles and I came across the problem gimbal lock which can occur by using Euler angles. In gimbal lock we lose one axis of rotation. But how? And when does it happen? On ...
3
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1answer
231 views

Improved Laplacian smoothing of noisy surface meshes

I have a question regarding Laplacian Smoothing of meshes and in particular the paper "Improved Laplacian smoothing of noisy surface meshes" by J. Vollmer in the early 2000's. What is the reason for ...
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0answers
44 views

Aligning similar surface meshes consistently

When I have a plaster cast of a mandibula and rest it upside down on a table, in most cases it will be in a stable position. In real life, I do not have a plaster cast, but a 3D scan, i.e. a surface ...
4
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1answer
1k views

Normal 2D photo to VR-compatible spherical photo

How to turn a normal photo like this one : into a photo that I can use in my game development platform (Unity3D). I just wrap a 3d sphere model with the photo and then it can be all around me when I ...
3
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2answers
287 views

Frustum aligned volume integration - aliasing issue - temporal reprojection

Raw volume raymarching especially aligned with frustum seem to produce a lot of aliasing/banding on edges of shadow map. Especially when fragment pos is far because step length is then getting bigger. ...
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1answer
2k views

Background behind 3D model

I have object loader, which i want to have background. I tried to put jpg image like texture to my application. I tried to make that with FreeImage library, but the image didn't show. Also i tried ...
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1answer
65 views
9
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1answer
1k views

Pipeline to create Voronoi Meshes

I would like to implement a Maya plugin (this question is independent from Maya) to create 3D Voronoi patterns, Something like I just know that I have to start from point sampling (I implemented the ...
5
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1answer
237 views

Creating Sparks using Code

I'm new to this area and have less knowledge. I want to create some graphics like sparks and lightning by writing some code, using my own physics. I don't want to use some engine, However I can use ...
5
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1answer
133 views

Where should I project a polygon corner when it is behind me?

I am creating a simple 3D engine as a learning project to get the hang on spherical trigonometry. I am using the following approach. 1. A model consists of a lot of triangular faces. 2. Each triangle ...
24
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1answer
821 views

Is my perspective math correct?

I've got a homework in which I have to calculate and plot some points using a pespective transformation, but I'm not sure my results are correct, since the 3d plot using Camera coordinates looks very ...
5
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1answer
283 views

Transformation Matrices

Consider the following problem and its answer: Given 3 points in 3D: $A=(A_x,A_y,A_z); B=(B_x,B_y,B_z) ; C=(C_x,C_y,C_z)$ Find the transformation matrix (in homogeneous coordinates) that ...
4
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1answer
196 views

Transformations about a Plane

I need to find the transformation matrix (homogeneous coordinates) that flips an object about a plane whose normal is directed towards (-2 2 0), and intersects the y-axis at y=2. I know how to do ...
5
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1answer
100 views

What other paradigms exist besides vector/fragment/transform graphics programming?

I am familiar with the basic concepts of writing vector and fragment shaders while using linear transformation matrices to describe orientations in 3D space. But, what other paradigms exist (...
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0answers
94 views

In a polygonal mesh 3d model which consist of triangles is it possible to separate different objects?

I have a 3d city model that is a collada file which consist of many triangles. When I select the model in a 3d software all buildings are selected. But I want every building to be selectable ...
4
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1answer
60 views

get partial view points from 3d surface mesh

I have a 3d surface mesh. Say the camera is located in some points and I want to get the visible points from the 3d surface mesh from the camera view. I believe this kind of process would be done ...
6
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1answer
504 views

Perspective correct interpolation of normal values

I'm currently writing a software rasterizer and I'm at the point where I can draw arbitrary triangles with vertex colors and perspective correct texture mapping. I do point and directional lighting by ...
3
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1answer
71 views

How can I draw a tube on basis of position and angle between two 3d points?

I'm struggling with this idea of creating two particles in 3d and draw a tube between them. I can't figure out how to properly set the angle of the tube. I've used two approaches: calculating the ...
3
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2answers
103 views

How to texturize a 3D model from video?

I have a base 3D mesh of an object that I want to texturize. I also have a 360 degrees video of the real-world object. What are good ways to use the video to texturize the mesh? Are there existing ...
4
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2answers
203 views

Implement own Bend function

I'm trying to write a mesh deformer that bends a Cube around an axis like this: The bend degree in figure A is 90 and something like 35 in B. So if I know my desired bend degree how can I get alpha? ...
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1answer
84 views

How to convert image results into data?

I have made an 3d solar exposure analysis for a 3d city model that determines how long a surface receive direct sunlight throughout the year. Results are coloured surfaces and legend of coloures that ...
1
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1answer
93 views

Optimal 2D graphics resource [closed]

I am a some-what experienced programer, and I have been working on creating a 3D graphics engine utilizing the OpenGL system, primarily focused on use in games. However, I also want to do some work ...
1
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0answers
339 views

Symmetry plane estimation for 3D point cloud

I have a question about finding the symmetry plane that separate the left and the right halves of a point cloud. We scanned an object, say a human face, with a 3D scanner, such as Kinect, which gives ...
3
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1answer
3k views

Calculate vanishing point

In perspective projection, group of parallel lines have the same vanishing point. I am interesting about the reverse calculation: Getting the group of parallel lines equations that their vanishing ...
3
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2answers
2k views

3D rotation matrix around vector

I am using matrix for performing 3D rotations. I know that in 3D space the matrix product order is important - changing the order of the matrices can effect the rotate result. So I am interesting ...
10
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1answer
15k views

What's the difference between orthographic and perspective projection?

I have been studying computer graphics, from the book Fundamentals of Computer Graphic (but the third edition), and I lastly read about projections. Though, I didn't exactly understand what's the ...
2
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2answers
831 views

How are hard and soft shadows cast?

I have been studying computer graphics, from the book Fundamentals of Computer Graphic (but the third edition), and I lastly read about texture mapping and shadow maps. Though, I didn't exactly ...
1
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1answer
587 views

Which 3D algorithms does Windows 10's “3D Builder” application use?

Windows 10 ships with "3D Builder", a Universal App that contains utility functions to prepare STL, OBJ, 3DS, and other files that represent geometries for 3D printing. The utility looks like this: ...