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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94 views

3D homogenous coordinates versus 4D homogenous coordinates

We know that any 2D point $(x, y) $which represents as 3D homogeneous coordinates is of the form $(x, y, 1)$ which is the points of projective plane $P^2.$ If I use the same concepts for 3D points $(...
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2answers
131 views

$(x, y, 1)$ is 2D homogenous coordinates or 3D homogenous coordinates?

We know that $(x, y, 1)$ are the homogenous coordinates of a 2D point $(x, y)$. $(x, y, 1)$ has 2 degrees of freedom. That's why we should call it 2D homogenous coordinates. But many websites say it's ...
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1answer
136 views

Perspective transformation is perspective projection? [duplicate]

I know that ( Reference )in transformation source and destination has same coordinates dimensions. But in projection destination coordinate system has fewer dimensions than the source coordinate ...
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23 views

How to compute centroidal power diagram for 3D objects?

In this paper, Packing Irregular Objects in 3D Space via Hybrid Optimization, the authors used the centroidal power diagram method to divide a container into $m$ subregions for $m$ irregular 3D ...
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5answers
902 views

Existence of vanishing point

Consider the following example of perspective projection: I have one railway track with two parallel lines meeting at the point $X$ at infinity which is the theoretical approach. This X is called the ...
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0answers
48 views

3D shearing w. r. t $x$-axis [closed]

Shearing in $X$ axis is achieved by using the following shearing equations- $X_{new} = X_{old}, Y_{new} = Y_{old} + Sh_y × X_{old}, Z_{new} = Z_{old} + Sh_z × X_{old}.$ My question is during $Y_{new}...
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1answer
130 views

Difference between 2D and 3D pipeline

2D transformation and viewing: The camera projects the 2D world co-ordinate $(x_w, y_w)$ on its projection plane which co-ordinates $(x_v, y_v)$. 3D transformation and viewing: The camera projects the ...
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2answers
100 views

Difference between perspective and parallel projection [closed]

We know that in orthographic Projection Projectors (projection vectors) are perpendicular to the projection plane. And in Perspective Projection Object positions are transformed to the view plane ...
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1answer
140 views

$P^2$ vs projection plane

I want to explain what I understood of definition of the two things. Projection plane: The general processing steps for modeling and converting a world coordinate description of a scene to device ...
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1answer
60 views

Calculating UV coordinates for sampling texture atlas

I have an 8192x8192 texture atlas that contains 1024x1024 shadow maps aligned side by side. I'm trying to calculate the uv coordinates so that I can sample each shadow map appropriately based on the '...
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1answer
93 views

OpenGL transparency - object behind is not rendered

I'm trying to implement voxel world using OpenGL (Core 3.3). I've come across a problem with transparency. It looks like sometimes GPU decides to not render stuff that would be important. Can you help ...
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1answer
54 views

Motivation behind tesselation

This question is NOT about the hardware difficulties and shortcomings of tesselation shaders I am trying to understand the motivation behind tesselation shaders. Why/when/where tesselation is a good ...
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65 views

Is it possible that a superior, undiscovered 3D rendering method exists?

As far as I know, the only options we have for true 3D rendering are polygonal rendering, ray-marching and raytracing/casting. Why is that? Surely there must be other ways? Is there some paper ...
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45 views

Methods to interpolate between 2 topologically identical 3D meshes

I have 2 3D surface meshes. These meshes have vertex-correspondence and have the same topology (same edges and triangles connecting the vertices). However, the vertex positions (3d coordinates) are ...
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0answers
40 views

Proprietary 3D Format Reverse Engineering: What Could These Numbers And Matrices Represent?

I'm trying to reverse engineer a model format from an older Russian game (Pathologic) with limited success. It is a proprietary model format not recognized by any converters/editing tools (believe me, ...
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2answers
100 views

Why do OBJ files contain so many duplicate vertices if they use indices to define faces?

I have been experimenting with loading in OBJ files into memory using tinyobj. I have also been learning and analysing the OBJ file format specification. I have some code which loads the BMW car model ...
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1answer
44 views

How to ensure that a randomly-generated velocity vector moves the camera forward within a valid arc?

I spawn a camera in a scene using random coordinates for x and y and setting z=0 and orient ...
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1answer
104 views

How does 3D graphic software adjust for distortion inherent in perspective projection?

As this question and its answers point out, projecting a sphere on a flat picture plane, with perspective projection, may result in a ellipse, not a circle, and my understanding is that the only way a ...
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0answers
37 views

Calculating the intersection of two volumes

What is an efficient way to calculate the volume of intersection of two arbitrary volumes described as closed surfaces? That is, with two meshes, A and B, how do I calculate the intersection of A and ...
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1answer
88 views

How compute new camera parameters given a velocity vector?

My goal is to update camera parameters given a velocity vector so that the camera points in the direction of the velocity vector. How should one compute the update matrix for the camera parameters?
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25 views

Convert point clouds into voxels

I have points that are obtained by sampling a mesh(which is not watertight). Now, I would like to convert that mesh into voxel? Does anyone have any suggestions for solving this problem?
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0answers
58 views

Why do materials have both an ambient color and a diffuse color?

One of the first things I learned about computer graphics lighting (and light in general) is that when a ray of light hits a surface, the surface absorbs certain colors and the light retains the rest. ...
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0answers
31 views

Is there a Performance Penalty for LOD objects with different topology?

I have a fairly complex-shaped object I've modeled, and in creating the LOD meshes, I've merged some verts, deleted some and even added some after in cases where this manipulation produced an n-gon. ...
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1answer
156 views

How do I extrude a 2D Bezier curve representation into a 3D solid using Python?

Where P is the control point, w is weight. I plan to extrude this 2d representation into 3d. I have a discrete 2D representation (array which has [n_points, 2, 1] for each sample) of an airfoil that ...
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3answers
1k views

How can I get a signed distance (SDF) from a mesh?

I am trying to use constructive solid geometry (CSG) and boolean operators to combine various shapes and get the outer (possibly concave) hull. This seems to work okay when using primitive shapes like ...
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83 views

Quadric Edge Collapse Decimation of an object for reducing number of its vertices damages the original shape of object

I have been using "Simplification: Quadric Edge Collapse Decimation" for simplifying my meshes to only have ~800 vertices and it has been working with a couple of meshes I tried. However, ...
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0answers
18 views

How to extrude a face from a selected mesh in Babylon,js using the ExtrudeShape method?

I'm trying to extrude a face from a selected mesh in Babylon.js using the ExtrudeShape but can't figure out why I got flipped faces. The bottom extrusions always comes flipped for a reason I ignore. ...
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47 views

UV coordinates calculation broken

I've tried using the classic formula of calculating barycentric coordinates. When the plane on which you are projecting the texture is collinear to any of the base vectors it crashes with a division ...
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0answers
22 views

How to draw a pdb 3d structure in webgl?

I am trying to create a 3d structure in webgl using 3d coordinates from a pdb file mentioned below: https://www.rcsb.org/structure/1RE2 I don't know which one is the appropriate one, so i used gl....
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17 views

Translate the camera with Pan gesture (when it is rotated )

I am new here I am not good in math SO what I need is I need to translate the 3D camera with Pan gesture on 2d Screen With below code it is working But if camera has some Euler Angle (rotated ) then I ...
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2answers
270 views

How does OBJ format determine vertex normals?

I have a very simple obj file: ...
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0answers
41 views

Under what conditions does a mesh operation cause the mesh become non-manifold and how to avoid it?

I'm implementing some mesh operations (e.g. edge collapse, edge split, edge flip etc) and need to ensure applying such operations does not cause the mesh to become non-manifold. However, I'm not sure ...
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1answer
18 views

Plotting points along a 3D line segment

I'm trying to plot some points along a 3D line segment and could really use some help. In 2D, I've found success getting the angle of the line, the sine & cosine of the angle, and then adding the ...
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1answer
317 views

What software was used to make KDA - Villain?

I want to try making small clips with realistic environment with the lighting in the KDA music video... Any ideas what kind of program to use?
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1answer
50 views

Calculating Material/Texture Placement from Bitmap to 3D Model

everyone! I am currently developing a program that converts a 3D model to 2D isometric pixel art. Part of my program extracts the texture from an FBX file (as FBX files can have textures built in), ...
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2answers
120 views

Why do some videos look smoother and others don't on the same monitor

I have a Dell monitor with 60 Hz refresh rate and therefore games playing on it are not very smooth as compared to 120 hz. But when I open videos on YouTube of the same game on the same monitor, some ...
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2answers
151 views

Mathematical Foundations of Radiative Transfer

I'm new to learning about ray tracing, but have been fairly confused by the mathematical foundations of it all. Specifically of radiometry/radiative transfer. I've internet searched a lot and skimmed ...
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44 views

3D Bouncing Cube

I'm trying to write a little program with a bouncing cube but I can't find the right x, y, z and angle for it. I have these lines: ...
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0answers
64 views

Atmospheric scattering band/seperation artifact

I am currently experimenting with some atmospheric scattering in glsl in my OpenGL engine. I am experiencing a strange phenomena where a strange band / separation artifact appears along the middle of ...
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1answer
78 views

How are obj files textured?

I am a new learner in 3d graphics. So forgive me if I seem to ask something very basic. I am confused how obj files are textured. So far I have seen: obj + jpg obj + mtl + jpg When I look online, ...
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3answers
101 views

Silhouette below 3D model

There are some 3D applications which can cast shadow or silhouette below 3D models. They render pretty fast and smooth. I wonder what kind of technology is the standard procedure to get 3D model ...
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23 views

Changing shader color

I have the following .fx file for my shader: ...
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2answers
82 views

What exactly is it about reality that is so difficult to recreate in a 3D simulation?

I have to admit that, while watching footage of the enhanced 2020 version of the 2018 game Forza Horizon 4, when they are driving fast, I have to sometimes remind myself that I am watching a video ...
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0answers
45 views

Algorithm to select regions based on curvature on a mesh

I'm trying to understand how to implement an algorithm similar to the one used by Magics' mark surface tool, you can see such behaviour on this video. Quoting the video: "Basically with this tool ...
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1answer
51 views

projecting 3d onto 2d plane is not showing up correctly

I am trying to learn about 3d graphics from first principles, so i have decided to implement a simple thing, create a circle in 3d space & rotate it along some axis. I understand the basics theory....
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1answer
351 views

Vertices, Vertex Normals and Face Normals

Using Open 3D Model Viewer, I have converted an OBJ file to an STL file. In the source file, the Vertex Normals are specified and in the destination, the face normal of the triangles are present which ...
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2answers
91 views

Rounding a 3D corner with Subdivisions

Following the instructions from this post on Stack Overflow, I have been able to find points A, B, and C from points V1, V2, and V3 and a radius value (code below). I would like to be able to find a ...
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0answers
39 views

Retaining hierarchy of assembly when converting STEP to GLTF

I want to convert STEP files to gLTF. I know that gLTF suuports hierarchy of assemblies and parts. Source: https://cadexchanger.com/blog/283-how-to-load-3d-cad-data-into-three-js-part-2 However, it is ...
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1answer
84 views

Blend Shape, Pose Blend Shape, and Shape Blend Shape

Since there is a lot of cross-section between computer vision and computer graphics for 3D pose and shape estimation of non-rigid objects, I would like to know what "blend shape", "pose ...
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1answer
35 views

Real 3D interior room from 360 images

If I have 360 images of an interior room from all different angles, would it be possible with current 3D software technology to create a real 3D representation of that room, where the camera could ...

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